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Lee DS, Fahey DW, Skowron A, Allen MR, Burkhardt U, Chen Q, Doherty SJ, Freeman S, Forster PM, Fuglestvedt J, Gettelman A, De León RR, Lim LL, Lund MT, Millar RJ, Owen B, Penner JE, Pitari G, Prather MJ, Sausen R, Wilcox LJ. The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018. Atmos Environ (1994) 2021; 244:117834. [PMID: 32895604 PMCID: PMC7468346 DOI: 10.1016/j.atmosenv.2020.117834] [Citation(s) in RCA: 90] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Revised: 07/02/2020] [Accepted: 07/30/2020] [Indexed: 05/04/2023]
Abstract
Global aviation operations contribute to anthropogenic climate change via a complex set of processes that lead to a net surface warming. Of importance are aviation emissions of carbon dioxide (CO2), nitrogen oxides (NOx), water vapor, soot and sulfate aerosols, and increased cloudiness due to contrail formation. Aviation grew strongly over the past decades (1960-2018) in terms of activity, with revenue passenger kilometers increasing from 109 to 8269 billion km yr-1, and in terms of climate change impacts, with CO2 emissions increasing by a factor of 6.8 to 1034 Tg CO2 yr-1. Over the period 2013-2018, the growth rates in both terms show a marked increase. Here, we present a new comprehensive and quantitative approach for evaluating aviation climate forcing terms. Both radiative forcing (RF) and effective radiative forcing (ERF) terms and their sums are calculated for the years 2000-2018. Contrail cirrus, consisting of linear contrails and the cirrus cloudiness arising from them, yields the largest positive net (warming) ERF term followed by CO2 and NOx emissions. The formation and emission of sulfate aerosol yields a negative (cooling) term. The mean contrail cirrus ERF/RF ratio of 0.42 indicates that contrail cirrus is less effective in surface warming than other terms. For 2018 the net aviation ERF is +100.9 milliwatts (mW) m-2 (5-95% likelihood range of (55, 145)) with major contributions from contrail cirrus (57.4 mW m-2), CO2 (34.3 mW m-2), and NOx (17.5 mW m-2). Non-CO2 terms sum to yield a net positive (warming) ERF that accounts for more than half (66%) of the aviation net ERF in 2018. Using normalization to aviation fuel use, the contribution of global aviation in 2011 was calculated to be 3.5 (4.0, 3.4) % of the net anthropogenic ERF of 2290 (1130, 3330) mW m-2. Uncertainty distributions (5%, 95%) show that non-CO2 forcing terms contribute about 8 times more than CO2 to the uncertainty in the aviation net ERF in 2018. The best estimates of the ERFs from aviation aerosol-cloud interactions for soot and sulfate remain undetermined. CO2-warming-equivalent emissions based on global warming potentials (GWP* method) indicate that aviation emissions are currently warming the climate at approximately three times the rate of that associated with aviation CO2 emissions alone. CO2 and NOx aviation emissions and cloud effects remain a continued focus of anthropogenic climate change research and policy discussions.
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Affiliation(s)
- D S Lee
- Faculty of Science and Engineering, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, M1 5GD, United Kingdom
| | - D W Fahey
- NOAA Chemical Sciences Laboratory (CSL), Boulder, CO, USA
| | - A Skowron
- Faculty of Science and Engineering, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, M1 5GD, United Kingdom
| | - M R Allen
- School of Geography and the Environment, University of Oxford, Oxford, UK
- Department of Physics, University of Oxford, Oxford, UK
| | - U Burkhardt
- Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
| | - Q Chen
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
| | - S J Doherty
- Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO, USA
| | - S Freeman
- Faculty of Science and Engineering, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, M1 5GD, United Kingdom
| | - P M Forster
- School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - J Fuglestvedt
- CICERO-Center for International Climate Research-Oslo, PO Box 1129, Blindern, 0318, Oslo, Norway
| | - A Gettelman
- National Center for Atmospheric Research, Boulder, CO, USA
| | - R R De León
- Faculty of Science and Engineering, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, M1 5GD, United Kingdom
| | - L L Lim
- Faculty of Science and Engineering, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, M1 5GD, United Kingdom
| | - M T Lund
- CICERO-Center for International Climate Research-Oslo, PO Box 1129, Blindern, 0318, Oslo, Norway
| | - R J Millar
- School of Geography and the Environment, University of Oxford, Oxford, UK
- Committee on Climate Change, 151 Buckingham Palace Road, London, SW1W 9SZ, UK
| | - B Owen
- Faculty of Science and Engineering, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, M1 5GD, United Kingdom
| | - J E Penner
- Department of Climate and Space Sciences and Engineering, University of Michigan, 2455 Hayward St., Ann Arbor, MI, 48109-2143, USA
| | - G Pitari
- Department of Physical and Chemical Sciences, Università dell'Aquila, Via Vetoio, 67100, L'Aquila, Italy
| | - M J Prather
- Department of Earth System Science, University of California, Irvine, 3329 Croul Hall, CA, 92697-3100, USA
| | - R Sausen
- Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
| | - L J Wilcox
- National Centre for Atmospheric Science, Department of Meteorology, University of Reading, Earley Gate, Reading, RG6 6BB, UK
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Affiliation(s)
- Q H Lim
- Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - L L Lim
- Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
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Affiliation(s)
- L L Lim
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong.,Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.,Asia Diabetes Foundation, Hong Kong
| | - J C N Chan
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong.,Asia Diabetes Foundation, Hong Kong.,Hong Kong Institute of Diabetes and Obesity, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong.,Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong
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Paramasivam SS, Chinna K, Singh AKK, Ratnasingam J, Ibrahim L, Lim LL, Tan ATB, Chan SP, Tan PC, Omar SZ, Bilous RW, Vethakkan SR. Continuous glucose monitoring results in lower HbA 1c in Malaysian women with insulin-treated gestational diabetes: a randomized controlled trial. Diabet Med 2018; 35:1118-1129. [PMID: 29663517 DOI: 10.1111/dme.13649] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/10/2018] [Indexed: 02/05/2023]
Abstract
AIMS To determine if therapeutic, retrospective continuous glucose monitoring (CGM) improves HbA1c with less hypoglycaemia in women with insulin-treated gestational diabetes mellitus (GDM). METHODS This prospective, randomized controlled, open-label trial evaluated 50 women with insulin-treated GDM randomized to either retrospective CGM (6-day sensor) at 28, 32 and 36 weeks' gestation (Group 1, CGM, n = 25) or usual antenatal care without CGM (Group 2, control, n = 25). All women performed seven-point capillary blood glucose (CBG) profiles at least 3 days per week and recorded hypoglycaemic events (symptomatic and asymptomatic CBG < 3.5 mmol/l; non-fasting < 4.0 mmol/l). HbA1c was measured at 28, 33 and 37 weeks. In Group 1, both CGM and CBG data were used to manage diabetes, whereas mothers in Group 2 were managed based on CBG data alone. RESULTS Baseline characteristics (age, pre-pregnancy BMI, HbA1c , total insulin dose) were similar between groups. There was a lower increase in HbA1c from 28 to 37 weeks' gestation in the CGM group [∆HbA1c : CGM + 1 mmol/mol (0.09%), control + 3mmol/mol (0.30%); P = 0.024]. Mean HbA1c remained unchanged throughout the trial in the CGM group, but increased significantly in controls as pregnancy advanced. Mean HbA1c in the CGM group was lower at 37 weeks compared with controls [33 ± 4 mmol/mol (5.2 ± 0.4%) vs. 38 ± 7 mmol/mol (5.6 ± 0.6%), P < 0.006]. Some 92% of the CGM group achieved an HbA1c ≤ 39 mmol/mol (≤ 5.8%) at 37 weeks compared with 68% of the control group (P = 0.012). Neither group experienced severe hypoglycaemia. CONCLUSION CGM use may be beneficial in insulin-treated GDM because it improves HbA1c compared with usual antenatal care without increasing severe hypoglycaemia. (Clinical Trials Registry No.: NCT02204657).
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Affiliation(s)
- S S Paramasivam
- Department of Medicine, University Malaya Medical Centre, Kuala Lumpur
| | - K Chinna
- Department of Social and Preventive Medicine, University Malaya Medical Centre, Kuala Lumpur
| | - A K K Singh
- Department of Medicine, Serdang Hospital, Selangor
| | - J Ratnasingam
- Department of Medicine, University Malaya Medical Centre, Kuala Lumpur
| | - L Ibrahim
- Department of Medicine, University Malaya Medical Centre, Kuala Lumpur
| | - L L Lim
- Department of Medicine, University Malaya Medical Centre, Kuala Lumpur
| | - A T B Tan
- Department of Medicine, University Malaya Medical Centre, Kuala Lumpur
| | - S P Chan
- Department of Medicine, University Malaya Medical Centre, Kuala Lumpur
| | - P C Tan
- Department of Obstetrics and Gynaecology, University Malaya Medical Centre, Kuala Lumpur
| | - S Z Omar
- Department of Medicine, Serdang Hospital, Selangor
| | - R W Bilous
- Newcastle University Malaysia (NUMed), Johor, Malaysia
| | - S R Vethakkan
- Department of Medicine, University Malaya Medical Centre, Kuala Lumpur
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Lim LL, Shah FZM, Ibrahim L, Paramasivam SS, Ratnasingam J, Chan SP, Tan ATB, Vethakkan SR. Hypopituitarism in a Dengue Shock Syndrome Survivor without known Pituitary Adenoma. Trop Biomed 2016; 33:746-752. [PMID: 33579071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Dengue infection is endemic in South East Asia and parts of the Americas. Dengue hemorrhagic fever is characterized by vascular permeability, coagulation-disorders and thrombocytopenia, which can culminate in hypotension i.e. dengue shock syndrome. Hypopituitarism arising as a complication of dengue is extremely rare. Hemorrhagic pituitary apoplexy of pre-existing pituitary adenomas has been rarely reported in dengue. We describe an uncommon case of hypopituitarism in a dengue shock syndrome survivor without known pituitary adenoma. A 49 years old nulliparous lady (from Kuala Lumpur, Malaysia) presented with typical symptoms of hypocortisolism. Postural hypotension was evident with normal secondary sexual characteristics. Further history revealed that she survived an episode of dengue shock syndrome 6 years ago where premature menopause developed immediately after discharge, and subsequently insidious onset of multiple hormonal deficiencies indicative of panhypopituitarism. There were no neuro-ophthalmological symptoms suggestive of pituitary apoplexy during hospitalization for severe dengue. Magnetic resonance imaging of the pituitary 6 years later revealed an empty sella. Autoimmune screen and anti-thyroid peroxidase antibodies were negative. We describe a rare possible causative association of severe dengue with panhypopituitarism without known pituitary adenoma, postulating pituitary infarction secondary to hypotension (mimicking Sheehan's syndrome), or a direct viral cytopathic effect. Subclinical pituitary apoplexy secondary to asymptomatic pituitary hemorrhage however cannot be excluded. Future research is required to determine the need for and timing of pituitary axis assessment among dengue shock syndrome survivors.
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Affiliation(s)
- L L Lim
- Division of Endocrinology, Department of Internal Medicine, University of Malaya, 59100 Kuala Lumpur, Malaysia
| | - F Z M Shah
- Division of Endocrinology, Department of Internal Medicine, University Technology of MARA, 47000 Sungai Buloh, Malaysia
| | - L Ibrahim
- Division of Endocrinology, Department of Internal Medicine, University of Malaya, 59100 Kuala Lumpur, Malaysia
| | - S S Paramasivam
- Division of Endocrinology, Department of Internal Medicine, University of Malaya, 59100 Kuala Lumpur, Malaysia
| | - J Ratnasingam
- Division of Endocrinology, Department of Internal Medicine, University of Malaya, 59100 Kuala Lumpur, Malaysia
| | - S P Chan
- Division of Endocrinology, Department of Internal Medicine, University of Malaya, 59100 Kuala Lumpur, Malaysia
| | - A T B Tan
- Division of Endocrinology, Department of Internal Medicine, University of Malaya, 59100 Kuala Lumpur, Malaysia
| | - S R Vethakkan
- Division of Endocrinology, Department of Internal Medicine, University of Malaya, 59100 Kuala Lumpur, Malaysia
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Abstract
The comprehensive overview of Asian-Pacific migration summarizes early population movements during the colonial period and describes the major types of contemporary Asian population movements: (1) environmental refugees, (2) political refugees, (3) internal population movements, (4) contract labor migration, (5) migration of permanent settlers, (6) business related movements and tourism. Projections of net international migration are given. Population growth, employment absorption and emigration pressures are likely to contribute to a large mobility potential for Asia, with significant implications for Australia.
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Abstract
The feminization of women in international labor migration has been most pronounced in the case of Asia, with women moving in their own right as economic migrants and faced with regulatory and social constraints, gender discrimination and exploitation in countries of origin and destination. Asian countries, both sending and receiving, have been experimenting with gender-sensitive migration policies and programs. This paper describes the characteristics of Asian female labor migration, examines policy dimensions and suggests action to bridge the gaps between policy dimensions and implementation.
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Ratnasingam J, Karim N, Paramasivam SS, Ibrahim L, Lim LL, Tan ATB, Vethakkan SR, Jalaludin A, Chan SP. Hypothalamic pituitary dysfunction amongst nasopharyngeal cancer survivors. Pituitary 2015; 18:448-55. [PMID: 25134488 DOI: 10.1007/s11102-014-0593-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
PURPOSE Radiation fields for nasopharyngeal cancer (NPC) include the base of skull, which places the hypothalamus and pituitary at risk of damage. We aimed to establish the prevalence, pattern and severity of hypothalamic pituitary (HP) dysfunction amongst NPC survivors. METHODS We studied 50 patients (31 males) with mean age 57 ± 12.2 years who had treatment for NPC between 3 and 21 years (median 8 years) without pre-existing HP disorder from other causes. All patients had a baseline cortisol, fT4, TSH, LH, FSH, oestradiol/testosterone, prolactin and renal function. All patients underwent dynamic testing with insulin tolerance test to assess the somatotroph and corticotroph axes. Baseline blood measurements were used to assess thyrotroph, gonadotroph and lactotroph function. RESULTS Hypopituitarism was present in 82% of patients, 30% single axis, 28% two axes, 18% three axes and 6% four axes deficiencies. Somatotroph deficiency was most common (78%) while corticotroph, gonadotroph and thyrotroph deficiencies were noted in 40% (4 complete/16 partial), 22 and 4% of the patients respectively. Hyperprolactinaemia was present in 30% of patients. The development of HP dysfunction was significantly associated with the time elapsed from irradiation, OR 2.5 (1.2, 5.3), p = 0.02, for every 2 years post treatment. The use of concurrent chemo-irradiation (CCRT) compared to those who had radiotherapy alone was also significantly associated with HP dysfunction, OR 14.5 (2.4, 87.7), p < 0.01. CONCLUSION Despite low awareness and detection rates, HP dysfunction post-NPC irradiation is common. Use of CCRT may augment time related pituitary damage. As these endocrinopathies result in significant morbidity and mortality we recommend periodic assessment of pituitary function amongst NPC survivors.
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Affiliation(s)
- J Ratnasingam
- Endocrine Unit, Department of Medicine, University Malaya Medical Centre, Kuala Lumpur, Malaysia,
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Ratnasingam J, Tan ATB, Vethakkan SR, Paramasivam SS, Ibrahim L, Lim LL, Choong K. Primary hyperparathyroidism: a rare cause of genu valgus in adolescence. J Clin Endocrinol Metab 2013; 98:869-70. [PMID: 23337722 DOI: 10.1210/jc.2012-3839] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- J Ratnasingam
- Endocrine Unit, Department of Medicine, University Malaya Medical Centre, 59100 Kuala Lumpur, Malaysia.
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Lim LG, Ho KY, Chan YH, Teoh PL, Khor CJ, Lim LL, Rajnakova A, Ong TZ, Yeoh KG. Urgent endoscopy is associated with lower mortality in high-risk but not low-risk nonvariceal upper gastrointestinal bleeding. Endoscopy 2011; 43:300-6. [PMID: 21360421 DOI: 10.1055/s-0030-1256110] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND AND STUDY AIMS The role of urgent endoscopy in high-risk nonvariceal upper gastrointestinal bleeding (NVUGIB) is unclear. The aim of this study was to determine whether esophagogastroduodenoscopy (EGD) performed sooner than the currently recommended 24 h in high-risk patients presenting with NVUGIB is associated with lower all-cause in-hospital mortality. METHODS All adult patients undergoing EGD for the indications of coffee-grounds vomitus, hematemesis or melena at a university hospital over an 18-month period were enrolled. Patients with variceal and lower gastrointestinal bleeding were excluded. Data were prospectively collected. RESULTS A total of 934 patients were included. The area under the receiver operating characteristic curve (AUROC) for the Glasgow-Blatchford score (GBS) was 0.813 for predicting all-cause in-hospital mortality, with a cut-off score of ≥ 12 resulting in 90 % specificity. In low-risk patients with GBS < 12, presentation-to-endoscopy time in those who died and in those who survived was similar. In high-risk patients with GBS of ≥ 12, presentation-to-endoscopy time was significantly longer in those who died than in those who survived. Multivariate analysis of the high-risk cohort showed presentation-to-endoscopy time to be the only factor associated with all-cause in-hospital mortality. For high-risk patients, the AUROC for presentation-to-endoscopy time in predicting all-cause in-hospital mortality was 0.803, with a sensitivity of 100 % at the cut-off time of 13 h. All-cause in-hospital mortality in high-risk patients was significantly higher in those with presentation-to-endoscopy time of > 13 h compared with those undergoing endoscopy in < 13 h from presentation (44 % vs. 0 %; P < 0.001). CONCLUSIONS Endoscopy within 13 h of presentation was associated with lower mortality in high-risk but not low-risk NVUGIB.
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Affiliation(s)
- L G Lim
- Department of Gastroenterology and Hepatology, National University Health System, Singapore
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Chan A, Lim LL, Tao M. Utilisation review of epoetin alfa in cancer patients at a cancer centre in Singapore. Singapore Med J 2009; 50:365-370. [PMID: 19421679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
INTRODUCTION Recombinant erythropoietin-stimulating agents have been used to ameliorate the symptoms of anaemia in cancer patients. However, there have been concerns about an increased risk of thromboembolic events and mortality. This study reviews the usage of epoetin alfa in treating chemotherapy-induced anaemia at the National Cancer Centre Singapore (NCCS), as well as the prescribing and monitoring practices employed. METHODS Cancer patients who have received at least one dose of epoetin alfa at the NCCS between January 1, 2005 and October 15, 2007 were included in this study. RESULTS A total of 121 patients were identified and 91 patients were eligible for data collection. The majority of patients manifested breast cancer (30.8 percent) and ovarian cancer (15.4 percent). Over 90 percent of the patients were receiving either chemotherapy or radiotherapy when epoetin alfa was initiated. Epoetin alfa was initiated at a median haemoglobin level of 8.7 (range 7-14.3) g/dL. Approximately 41.8 percent of the patients had a positive response after the initiation of epoetin alfa. Baseline iron studies were performed in 12.1 percent of the patients. Blood pressure was uncontrolled, according to the Singapore Ministry of Health Hypertension guideline, in a substantial number of patients (32.6 percent) prior to the initiation epoetin alfa. There were no documented thromboembolic events. CONCLUSION This study identified a broad range of practices in the utilisation of epoetin alfa at NCCS, which may explain the variable patient response to epoetin alfa. The results of this study will be used to improve the management of chemotherapy-induced anaemia at the institution.
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Affiliation(s)
- A Chan
- Department of Pharmacy, Faculty of Science, National University of Singapore, Block S4, 18 Science Drive 4, Singapore.
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Lim LL, Cheung N, Wang JJ, Islam FMA, Mitchell P, Saw SM, Aung T, Wong TY. Prevalence and risk factors of retinal vein occlusion in an Asian population. Br J Ophthalmol 2008; 92:1316-9. [PMID: 18684751 DOI: 10.1136/bjo.2008.140640] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- L L Lim
- Centre for Eye Research Australia, University of Melbourne, Australia
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Affiliation(s)
- Y L Lo
- Department of Neurology, National Neuroscience Institute, Singapore General Hospital, Singapore.
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Paul Chen J, Lim LL. Recovery of precious metals by an electrochemical deposition method. Chemosphere 2005; 60:1384-92. [PMID: 16054907 DOI: 10.1016/j.chemosphere.2005.02.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2003] [Revised: 02/01/2005] [Accepted: 02/01/2005] [Indexed: 05/03/2023]
Abstract
Conversion of soluble precious metals into a solid form for further reuse was studied by using an electrochemical deposition approach. It was found that the metal recovery followed a first-order reaction kinetics. The distance between the electrodes had no much impact on the recovery, while higher mixing led to faster kinetics. The presence of humic acid (HA) with lower concentration (<20mg l (-1)) did not have impact on the recovery. When its concentration was increased to 50 mg l (-1), it decreased the metal reduction. Presence of ethylene diamine tetraacetic acid (EDTA) and ionic strength slightly reduced the copper recovery rate. Around 50% removal of for HA and EDTA was achieved. In the competing environment, metal recovery was in the following order: silver>lead>copper. X-ray photoelectron spectroscopic and scanning electronic microscopic analysis of the reduced metals demonstrated that the depositions were composed of mainly elemental metals together with their oxides which were due to the oxidation.
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Affiliation(s)
- J Paul Chen
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore.
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Abstract
BACKGROUND Chronic hepatitis B virus carriers receiving chemotherapy develop a high hepatitis B virus reactivation rate (38-53%) with a high mortality (37-60%). Few studies have characterized the efficacy of lamivudine in the treatment of chemotherapy-induced hepatitis B virus reactivation. AIM To determine whether lamivudine prophylaxis reduces chemotherapy-induced hepatitis B virus reactivation and mortality. METHODS The medical records of all hepatitis B surface antigen-positive patients with malignancy treated with chemotherapy since 1995 at the National University Hospital of Singapore were identified, and divided into those who received lamivudine prophylaxis before chemotherapy (P) and those who did not (NP). The parameters examined included gender, age, malignancy type, steroid usage, number of chemotherapy courses and regimens, follow-up duration and hepatitis B virus status. The outcome measures were hepatitis B virus reactivation (abrupt rise of serum alanine aminotransferase to > 200 IU/L) and reactivation death. Patients with primary hepatoma or liver metastasis were excluded. RESULTS Thirty-five patients were identified: 16 in the P group and 19 in the NP group. The baseline characteristics of the two groups were similar. Seven of the 19 patients in the NP group and none of the 16 patients in the P group developed reactivation (36.8% vs. 0%, P=0.009). Six of the seven patients in the NP group who developed reactivation received lamivudine at that time, but five died (mortality, 71.4%), whilst no patient in the P group died from reactivation (P=0.064). CONCLUSIONS Prophylactic lamivudine appears to prevent hepatitis B virus reactivation and its associated mortality in patients treated with chemotherapy. This should be confirmed with prospective studies.
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Affiliation(s)
- L L Lim
- Department of Medicine, National University Hospital, Singapore.
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Abstract
"Exploring the unique experience of migration transition in Malaysia, this paper identifies the turning points in relation to the level and nature of economic and labor market developments in Malaysia. Examining the development dynamics that mark the passage from exporting labor to depending on foreign labor, the paper concludes that such dynamics are influenced not only by economic but also sociocultural, demographic and policy factors. Several lessons from the Malaysian experience are drawn at the end to be utilized by other countries that still have to reach the turning points of the migration transition."
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Lim LL. [Immigration and economic development in Eastern Asia]. Polit Etrang 2002; 59:761-81. [PMID: 12346374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
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Abstract
Most of the commonly used metal waste treatment approaches only allow removal of metals which are ultimately discarded as sludge and do not permit the reuse of the metals, resulting in a waste of raw materials. In this study, the recovery of precious metals of sliver and copper in a synthesized wastewater in batch reactors was investigated using a reduction method by hydrazine as the reducing agent. Recovery of metal ions was greatest at pH > 11. The presence of humic acid did not have negative effects on the recovery process. Varying dissolved oxygen levels in the hydrazine solution did not significantly affect the recovery of both metals while seeding and ageing processes resulted in an increase in the particle size of the solid obtained. Under competitive conditions between Cu2+ and Ag+ ions, the recovery of silver remained the same, while that of copper was enhanced.
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Abstract
A sample of 945 cardiac patients admitted under emergency conditions completed a quality of life questionnaire 4 months post-discharge. Half (471) were randomly allocated to a group used to develop a logistic regression model to predict mortality and cardiovascular morbidity 8 months later. Age 65-85 years, ever having heart failure, experiencing another cardiovascular event since discharge, and low global quality of life (QOL) score were found to be predictive of these outcomes; an interaction between QOL and heart failure was also found. The model was used to formulate a risk index which was validated in the remaining 474 patients. The index defines four levels of increasing risk of adverse outcomes, with rates in the development and validation groups, respectively, of: low risk 4% and 9%; moderate risk 13% and 15%; high risk 31% and 33%; very high risk 52% and 40%. Scores in the emotional, physical and social QOL domains were also found to be predictive of adverse outcomes, suggesting that interventions in any of these areas may prove beneficial. The index may be useful for follow-up evaluation of cardiac patients.
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Affiliation(s)
- T Dixon
- Cardiovascular Disease and Risk Factor Monitoring Unit, Australian Institute of Health and Welfare, 6A Traeger Court, 2617, Bruce ACT, Australia.
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Abstract
The objective of this study was to develop a simplified scoring system to predict 30-day mortality in patients with acute ischemic stroke. A retrospective cohort study was performed in a tertiary referral hospital in the Hunter Region of Australia. A prognostic index was created by assigning points to the variables in a Cox model. The index included impaired consciousness (5 points), dysphagia (3 points), urinary incontinence (4 points), admission body temperature higher than 36.5 degrees C (2 points), and hyperglycemia without a clinical history of diabetes (2 points). A score of 11 or more defined a high-risk group. The index achieved a sensitivity, specificity, and positive predictive value of 68%, 98% and 75%, respectively, in the derivation sample and 57%, 97% and 68%, respectively, in the validation sample. The results provide a simple risk stratification instrument for clinical research and practice. Further evaluation of the model in a prospective cohort is warranted
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Affiliation(s)
- Y Wang
- Centre for Clinical Epidemiology and Biostatistics, David Maddison Clinical Sciences Building, Royal Newcastle Hospital, Newcastle, New South Wales 2300, Australia.
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Abstract
The objective of this study was to determine the accuracy of administrative data (by use of hospital discharge codes) for measuring comorbidity in patients with heart disease. One thousand seven hundred and sixty-five medical records of subjects admitted to hospital for AMI, unstable angina, angina pectoris, chronic IHD or heart failure were reviewed. The number and types of comorbidities were determined from the medical records (regarded as the "gold standard"). These were compared with the 10 discharge codes obtained from the hospital administrative records (referred to as the "administrative data"). The rate of false-negative and false-positive comorbidity diagnoses were determined. Twenty of the 21 comorbidities studied were underreported in the administrative data. For these 20 comorbidities, the median false-negative rate was 49.5% and ranged from 11% for diabetes to 100% for dementia. False-positive rates were low, less than 1.5%, except for chronic arrythmia (4.8%) and hypertension (4.2%). Mean percent agreement was high, ranging from 88% for hypertension to 100% for AIDS/HIV. Administrative data based on hospital discharge codes consistently underestimate the presence of comorbid conditions in our population. This has implications for administrators when estimating mortality, length of stay and disability. Researchers also need to be aware when using administrative data based on hospital discharge codes to assess subject's comorbidities that they may be widely underreported.
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Affiliation(s)
- H Powell
- Department of Respiratory and Sleep Medicine, John Hunter Hospital, Locked Bag 1, Hunter Region Mail Centre, Newcastle, NSW 2310, Australia.
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Abstract
STUDY OBJECTIVE To examine the hospital management of unstable angina (UAP) in 1996 and 1998, according to patient demographic variables and disease severity. DESIGN Medical record review. SETTING 37 hospitals across New South Wales, Australia, representative of the secondary and tertiary care hospitals in the State. PARTICIPANTS All patients (or a random sample of patients) with UAP admitted to these hospitals during five months in 1996 and six months in 1998 (1872 and 1368 patients respectively). MAIN RESULTS In the two years between 1996 and 1998, there was an increase in the use of beta blockers and a corresponding decrease in the use of calcium channel blockers, as well as a decrease in the use of intravenous nitrates. Those aged 75 or more were roughly half as likely as those aged less than 65 to be prescribed heparin, aspirin and heparin, beta blockers, intravenous nitrates, and only one third as likely to be offered coronary angiography in hospital. They were one and a half times as likely to be prescribed calcium channel blockers compared with the youngest age group. A similar pattern was seen for gender, where men were more likely than women to be given aspirin, aspirin and heparin, and coronary angiography, and less likely to be given calcium channel blockers. Those with a past history were less likely, and those with more severe disease were more likely than others to be given most interventions. CONCLUSIONS In view of the low use of evidence-based management of UAP among women and the elderly, it would seem appropriate for disease management guidelines to target these groups.
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Affiliation(s)
- R F Heller
- Centre for Clinical Epidemiology and Biostatistics, Faculty of Medicine and Health Sciences, The University of Newcastle, NSW, Australia.
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Abstract
PURPOSE Catamenial epilepsy is a condition characterized by an increase in seizures during particular phases of the menstrual cycle. The incidence of catamenial epilepsy varies widely, partly because of a lack of a universally adopted definition. Specific treatment options for these patients are limited. The use of acetazolamide (AZ) has been based largely on anecdotal reports demonstrating efficacy in small or poorly characterized populations. The purpose of this study was to analyze retrospectively the efficacy, safety profile, and tolerability of AZ in women with catamenial epilepsy. METHODS Women with catamenial epilepsy identified from 1990 through 1999 were invited to participate in a retrospective telephone questionnaire addressing the relationship of seizures and the menstrual cycle and the use, efficacy, and adverse effects of AZ. Seizure outcome was classified as: seizure free (SF), significantly improved (SI), or not significantly improved (NSI). Responses to AZ were compared in women with different types of epilepsy and comparing continuous versus intermittent dosing using Fisher's exact tests. RESULTS Twenty women were identified who had received or were currently taking AZ. The drug was given continuously in 55% and intermittently in 45% of patients. A > or =50% decrease in the seizure frequency was reported by 40% of subjects. Response rates were similar in generalized and focal epilepsy and in temporal and extratemporal epilepsy. There was no significant difference in effectiveness comparing continuous with intermittent dosing. A loss of efficacy over 6-24 months was reported by 15% of women. CONCLUSIONS Despite our small sample and retrospective design, AZ appears to demonstrate efficacy for catamenial epilepsy.
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Affiliation(s)
- L L Lim
- Department of Neurology, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, U.S.A
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Abstract
OBJECTIVES To examine the benefits of a guideline-based educational program to improve management of unstable angina pectoris (UAP) in hospital patients. DESIGN Randomised controlled trial. SETTING 37 public hospitals across New South Wales. PATIENTS 1,872 patients admitted with a diagnosis of UAP between 1 February and 30 June 1996 (baseline survey), and 1,368 patients with the same diagnosis admitted between 1 July and 31 December 1998 (follow-up survey). INTERVENTION Educational sessions run by local opinion leaders, presenting guidelines on management of UAP from the National Health and Medical Research Council and feedback on local practice using data from the baseline survey. Sessions were run between March and June 1998. MAIN OUTCOME MEASURES Use of evidence-based practice, identified by review of medical records. RESULTS Use of beta-blockers increased in intervention and control hospitals, although the increase was significant only in the former. Use of calcium-channel blockers decreased significantly in both intervention and control hospitals. However, the change in drug use between baseline and follow-up did not differ significantly between intervention and control hospitals. CONCLUSIONS Despite some appropriate changes in drug use for UAP management between 1996 and 1998, there was no evidence that a guideline-based educational program was of benefit in changing management. This reaffirms the difficulty of changing doctors' behaviour through practice guidelines. Alternative methods of encouraging evidence-based practice should be considered.
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Affiliation(s)
- R F Heller
- Centre for Clinical Epidemiology and Biostatistics, Faculty of Medicine and Health Sciences, University of Newcastle, NSW.
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25
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Brennan ML, Anderson MM, Shih DM, Qu XD, Wang X, Mehta AC, Lim LL, Shi W, Hazen SL, Jacob JS, Crowley JR, Heinecke JW, Lusis AJ. Increased atherosclerosis in myeloperoxidase-deficient mice. J Clin Invest 2001; 107:419-30. [PMID: 11181641 PMCID: PMC199241 DOI: 10.1172/jci8797] [Citation(s) in RCA: 250] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Myeloperoxidase (MPO), a heme enzyme secreted by activated phagocytes, generates an array of oxidants proposed to play critical roles in host defense and local tissue damage. Both MPO and its reaction products are present in human atherosclerotic plaque, and it has been proposed that MPO oxidatively modifies targets in the artery wall. We have now generated MPO-deficient mice, and show here that neutrophils from homozygous mutants lack peroxidase and chlorination activity in vitro and fail to generate chlorotyrosine or to kill Candida albicans in vivo. To examine the potential role of MPO in atherosclerosis, we subjected LDL receptor-deficient mice to lethal irradiation, repopulated their marrow with MPO-deficient or wild-type cells, and provided them a high-fat, high-cholesterol diet for 14 weeks. White cell counts and plasma lipoprotein profiles were similar between the two groups at sacrifice. Cross-sectional analysis of the aorta indicated that lesions in MPO-deficient mice were about 50% larger than controls. Similar results were obtained in a genetic cross with LDL receptor-deficient mice. In contrast to advanced human atherosclerotic lesions, the chlorotyrosine content of aortic lesions from wild-type as well as MPO-deficient mice was essentially undetectable. These data suggest an unexpected, protective role for MPO-generated reactive intermediates in murine atherosclerosis. They also identify an important distinction between murine and human atherosclerosis with regard to the potential involvement of MPO in protein oxidation.
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Affiliation(s)
- M L Brennan
- Department of Microbiology, Immunology and Molecular Genetics, University of California-Los Angeles (UCLA), Los Angeles, California, USA
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26
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Abstract
BACKGROUND The influence of hyperglycemia on stroke mortality is controversial. The aim of this study was to investigate the prognostic role of hyperglycemia and diabetes on short-term and long-term mortality in patients with acute ischemic stroke. METHODS This retrospective cohort study included 416 acute ischemic stroke patients admitted to a tertiary hospital between July 1, 1995 and June 30, 1997. In-hospital mortality and 1-year mortality after discharge were the outcomes of the study. All patients were classified into four groups according to the glucose status and history of diabetes: group 1, normoglycemic without diabetes; group 2, normoglycemic with diabetes; group 3, hyperglycemic with diabetes and group 4, hyperglycemic without diabetes. Cochrane-Armitage trend test was used to assess the trend of mortality across the 4 groups. The influence of hyperglycemia on in-hospital and 1-year mortality were studied by logistic regression and Cox proportional hazards regression adjusting for confounders. RESULTS The Cochrane-Armitage trend test showed there was a strong trend towards increasing in-hospital mortality across groups 1 to 4 (P < .001). Hyperglycemia without a history of diabetes was an independent predictor of in-hospital mortality, odds ratio 3.0 (95% confidence interval: 1.1-8.3; P = .035). Hyperglycemia (with or without diabetes) did not predict in-hospital mortality significantly. Neither hyperglycemia per se nor hyperglycemia without a history of diabetes were significant in predicting 1-year mortality. CONCLUSION Hyperglycemia without diabetes is independently associated with higher in-hospital mortality in patients with acute ischemic stroke. There was a trend to increasing in-hospital mortality across groups 1 to 4.
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Affiliation(s)
- Y Wang
- Centre for Clinical Epidemiology and Biostatistics, Royal Newcastle Hospital, Newcastle, New South Wales, Australia
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Heller RF, O'Connell RL, D'Este C, Lim LL, Fletcher PJ. Differences in cardiac procedures among patients in metropolitan and non-metropolitan hospitals in New South Wales after acute myocardial infarction and angina. Aust J Rural Health 2000; 8:310-7. [PMID: 11894790 DOI: 10.1046/j.1440-1584.2000.00300.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An observational cohort study examined the difference in use of cardiac procedures during and after hospital admission for acute chest pain in 47 metropolitan or non-metropolitan hospitals across New South Wales (NSW). There were 3836 patients, represented by 4151 admissions to hospital after acute myocardial infarction (AMI), unstable angina or other angina. Follow up at 22 months was completed on 1695 patients. Patients admitted to metropolitan hospitals had higher rates of most cardiac procedures while in-patients than did patients in non-metropolitan hospitals. Odds ratios (95% confidence intervals) for the use of exercise stress tests, echocardiograms, nuclear studies and coronary angiography were 3.30 (1.38, 7.90), 9.34 (4.07, 21.44), 4.87 (2.08, 11.39) and 68.64 (17.29, 272.49), respectively, for patients with AMI and 1.93 (0.91, 4.12), 5.60 (1.60, 19.57), 3.51 (1.48, 8.33) and 38.57 (9.36, 158.94), respectively, for patients with unstable angina. Rates were similar between hospital types during the 22 months after discharge. The appropriateness of this large variation in resource use between metropolitan and non-metropolitan hospitals requires examination.
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Affiliation(s)
- R F Heller
- Centre for Clinical Epidemiology and Biostatistics, Faculty of Medicine and Health Sciences, University of Newcastle, Newcastle, New South Wales, Australia
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Vu HD, Heller RF, Lim LL, D'Este C, O'Connell RL. Mortality after acute myocardial infarction is lower in metropolitan regions than in non-metropolitan regions. J Epidemiol Community Health 2000; 54:590-5. [PMID: 10890870 PMCID: PMC1731723 DOI: 10.1136/jech.54.8.590] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
STUDY OBJECTIVES To compare in-hospital mortality for acute myocardial infarction (AMI) between metropolitan and non-metropolitan hospitals after adjustment for patients' severity; to examine the role of the use of effective cardiac medications in the possible mortality difference between these types of hospital. DESIGN Retrospective cohort study. SETTING 47 acute public hospitals in metropolitan and non-metropolitan areas of New South Wales, Australia, taking part in the Acute Cardiac Care Project based on medical record review. PATIENTS 1665 patients with principal discharge diagnosis of AMI from February to June 1996. MAIN RESULTS There was no difference in crude mortality rate (assessed as seven day mortality) between metropolitan and non-metropolitan hospitals (11.0% compared with 10.7% respectively, p=0.893). After adjustment for severity in a logistic regression model, the odds of death in non-metropolitan hospitals was significantly higher than in metropolitan hospitals (odds ratio = 1. 90; 95% CI 1.21, 3.23). The addition of the use of effective cardiac medications to the model resulted in the difference between hospital type becoming non-significant (odds ratio=1.09; 95% CI 0.57, 2.07). CONCLUSIONS In-hospital mortality in non-metropolitan hospitals was higher than that in metropolitan hospitals, after adjustment for patients' severity. This might partly be explained by the difference in use of effective cardiac medications between hospital type.
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Affiliation(s)
- H D Vu
- Centre for Clinical Epidemiology and Biostatistics, The University of Newcastle, David Maddison Clinical Sciences Building, Royal Newcastle Hospital, Newcastle NSW 2300, Australia
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29
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Page J, Heller RF, Kinlay S, Lim LL, Qian W, Suping Z, Kongpatanakul S, Akhtar M, Khedr S, Macharia W. Where do developing World clinicians obtain evidence for practice: a case study on pneumonia. J Clin Epidemiol 2000; 53:669-75. [PMID: 10941942 DOI: 10.1016/s0895-4356(99)00231-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
There are few data on the practice of evidence based medicine in the developing world, nor on the actual sources of evidence that clinicians use in practice. To test the hypothesis that there was variation between and within developing countries in the proposed management of a patient with hospital acquired pneumonia, and that part of the variation can be explained by the sources of evidence used. Questionnaire responses to hypothetical case history. Investigators from 6 centres within the International Clinical Epidemiology Network (INCLEN) in China, Thailand, India, Egypt, and Kenya. Doctors chosen to represent primary and secondary hospital practice in the regions of the study centres. Investigations and initial treatments which would be ordered for a hypothetical 60-year-old woman who develops pneumonia 5 days after hospital admission, whether local data on antibiotic sensitivities are available and where information would be obtained to guide management. Chest x-ray and sputum gram stain/culture were consistently the most commonly ordered investigations, there being much greater variation in the initial treatment choices with either penicillin, a third-generation cephalosporin or aminoglycoside being the most popular choice. Textbooks were the commonest form of information source, and access to a library, textbooks and journals were statistically significantly associated with appropriate choice of investigations, but not treatment. Access to local antibiotic sensitivities was associated with appropriate initial treatment choice. Improving access to information in the literature and to local data may increase the practice of evidence-based medicine in the developing world.
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Affiliation(s)
- J Page
- Centre for Clinical Epidemiology and Biostatistics, The Univeristy of Newcastle, Australia
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Abstract
OBJECTIVE To report on the nature, incidence and severity of problems commonly experienced by cardiac patients in the early months of recovery, and to test the hypotheses that there exist differences in the incidences of these problems depending on age and sex. METHODS 1124 emergency cardiac patients discharged from hospital with acute myocardial infarction, unstable angina, stable angina pectoris, chronic ischaemic heart disease or heart failure were surveyed 4 months after discharge. They were asked to indicate how often during the previous 2 weeks they had experienced each of a range of feelings and problems common to cardiac patients. RESULTS A large proportion of patients reported experiencing problems in the areas of emotional reactions (70%), physical condition (79%), convalescence (67%) and relating to family and friends (63%). Severe problems were experienced especially in the physical and convalescence areas (43% and 44%, respectively). A greater proportion of patients diagnosed with heart failure experienced problems than those with other diagnoses, and these problems were more severe. Amongst myocardial infarction patients, a greater proportion of females than males reported severe problems in the emotional and physical areas, and patients 65 years and over were more likely than younger patients to report experiencing severe problems with physical condition. CONCLUSIONS Many cardiac patients are experiencing psychosocial problems 4 months after hospital discharge, especially with physical activities and convalescence. A knowledge of the incidence and nature of these problems may help nurses to assist patients to validate their experiences.
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Affiliation(s)
- T Dixon
- Statistical Assistant, Centre for Clinical Epidemiology and Biostatistics, The University of Newcastle, Newcastle, Australia.
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Heller RF, Fisher JD, D'Este CA, Lim LL, Dobson AJ, Porter R. Death and readmission in the year after hospital admission with cardiovascular disease: the Hunter Area Heart and Stroke Register. Med J Aust 2000; 172:261-5. [PMID: 10860090 DOI: 10.5694/j.1326-5377.2000.tb123940.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVES To compare outcomes one year after hospital admission for patients initially discharged with a diagnosis of acute myocardial infarction (AMI), other ischaemic heart disease (other IHD), congestive heart failure (CHF) or stroke. DESIGN Cohort study. SETTING Hunter Area Heart and Stroke Register, which registers all patients admitted with heart disease or stroke to any of the 22 hospitals in the Hunter Area Health Service in New South Wales. PATIENTS 4981 patients with AMI, other IHD, CHF or stroke admitted to hospital as an emergency between 1 July 1995 and 30 June 1997 and followed for at least one year. MAIN OUTCOME MEASURES Death from any cause or emergency hospital readmission for cardiovascular disease. RESULTS In-hospital mortality varied from 1% of those with other IHD to 22% of those with stroke. Almost a third of all patients discharged alive (and 38% of those aged 70 or more) had died or been readmitted within one year. This varied from 22% of those with stroke to 49% of those with CHF. The causes of death and readmission were from a spectrum of cardiovascular disease, regardless of the cause of the original hospital admission. CONCLUSIONS Data from this population register show the poor outcome, especially with increasing age, among patients admitted to hospital with cardiovascular disease. This should alert us to determine whether optimal secondary prevention strategies are being adopted among such patients.
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Affiliation(s)
- R F Heller
- Centre for Clinical Epidemiology and Biostatistics, Faculty of Medicine and Health Sciences, University of Newcastle, NSW.
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Abstract
OBJECTIVES To examine the variation in stated management of acute myocardial infarction (AMI) among clinicians of different specialties, and to compare stated with actual practice. DESIGN Mail survey using a hypothetical case history, and review of medical records. SETTING 47 public hospitals in New South Wales. SUBJECTS 224 cardiologists, general/other physicians and general practitioners (GPs) who manage patients with AMI; 390 patients admitted for AMI between February and June 1996. OUTCOME MEASURES Stated and actual use of treatments and investigations for AMI. RESULTS Stated use of aspirin, thrombolysis and beta-blockers (95%-100%, 95%-100% and 80%-86%, respectively) was high in all three specialties. Cardiologists were significantly more likely than GPs to state use of heparin (87% v 57%; P < 0.001), ACE inhibitors (84% v 49%; P < 0.001) and echocardiography or gated pool heart scan (79% v 26%; P < 0.001). Stated use of nitrates by cardiologists was significantly lower compared with the other specialties (29% v 50% and 44%; P = 0.027). Actual use of aspirin was high (> 80%) in all specialties. Actual use of thrombolysis was similar to stated use after adjusting for factors such as time to hospital arrival and ST-segment elevation. There were substantial differences between stated and actual use. CONCLUSIONS There were differences in practice patterns between and among clinicians of different specialties in NSW, consistent with findings from other countries. The high stated and actual use of aspirin and thrombolysis is encouraging.
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Affiliation(s)
- L L Lim
- Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, NSW.
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O'Connell RL, Lim LL. Utility of the Charlson comorbidity index computed from routinely collected hospital discharge diagnosis codes. Methods Inf Med 2000; 39:7-11. [PMID: 10786063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
This study aims to determine whether the Charlson comorbidity index computed from ICD-9-CM discharge diagnosis codes adds additional information to a model containing adjustment for more informed patient details (e.g., disease severity and history), besides solely age and sex, when predicting long-term survival. We conducted a retrospective cohort study of patients admitted to hospital for suspected acute myocardial infarction. Index scores were calculated by applying the D'Hoore et al. algorithm (1993). The index significantly improved the model fit (likelihood ratio test: p < 0.001). The D'Hoore-adapted Charlson index is a useful comorbidity risk adjustment tool when applied to AMI and angina patients.
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Affiliation(s)
- R L O'Connell
- Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, Australia.
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Abstract
BACKGROUND AND PURPOSE The influence of body temperature on stroke outcome remains uncertain. The aim of this study was to investigate the prognostic role of admission body temperature on short-term and long-term mortality in a retrospective cohort study of patients with acute stroke. METHODS A retrospective cohort of 509 patients with acute stroke, admitted to a tertiary hospital between July 1, 1995, and June 30, 1997, was studied. The relationship between admission body temperature and mortality both in-hospital and at 1-year mortality was evaluated. Body temperature on admission was classified as hypothermia (</=36.5 degrees C), normothermia (>36.5 degrees C and </=37.5 degrees C), and hyperthermia (>37.5 degrees C). Logistic regression and proportional hazards function analysis were performed after adjustment for clinical predictors of stroke outcome. RESULTS In ischemic stoke, mortality was lower among patients with hypothermia and higher among patients with hyperthermia. The odds ratio for in-hospital mortality in hypothermic versus normothermic patients was 0.1 (95% CI, 0.02 to 0.5). The relative risk for 1-year mortality of hyperthermic versus normothermic patients was 3.4 (95% CI, 1.6 to 7.3). A similar but nonsignificant trend for in-hospital mortality was seen among patients with hemorrhagic stroke. CONCLUSIONS An association between admission body temperature and stroke mortality was noted independent of clinical variables of stroke severity. Hyperthermia was associated with an increase in 1-year mortality. Hypothermia was associated with a reduction in in-hospital mortality.
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Affiliation(s)
- Y Wang
- Centre for Clinical Epidemiology and Biostatistics, Royal Newcastle Hospital, New South Wales, Australia.
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35
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Abstract
Many extensions of survival models based on the Cox proportional hazards approach have been proposed to handle clustered or multiple event data. Of particular note are five Cox-based models for recurrent event data: Andersen and Gill (AG); Wei, Lin and Weissfeld (WLW); Prentice, Williams and Peterson, total time (PWP-CP) and gap time (PWP-GT); and Lee, Wei and Amato (LWA). Some authors have compared these models by observing differences that arise from fitting the models to real and simulated data. However, no attempt has been made to systematically identify the components of the models that are appropriate for recurrent event data. We propose a systematic way of characterizing such Cox-based models using four key components: risk intervals; baseline hazard; risk set, and correlation adjustment. From the definitions of risk interval and risk set there are conceptually seven such Cox-based models that are permissible, five of which are those previously identified. The two new variant models are termed the 'total time - restricted' (TT-R) and 'gap time - unrestricted' (GT-UR) models. The aim of the paper is to determine which models are appropriate for recurrent event data using the key components. The models are fitted to simulated data sets and to a data set of childhood recurrent infectious diseases. The LWA model is not appropriate for recurrent event data because it allows a subject to be at risk several times for the same event. The WLW model overestimates treatment effect and is not recommended. We conclude that PWP-GT and TT-R are useful models for analysing recurrent event data, providing answers to slightly different research questions. Further, applying a robust variance to any of these models does not adequately account for within-subject correlation.
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Affiliation(s)
- P J Kelly
- Centre for Clinical Epidemiology and Biostatistics, The University of Newcastle, Level 3, David Maddison Building, Royal Newcastle Hospital, Newcastle, NSW, 2300, Australia.
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36
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Abstract
Many extensions of survival models based on the Cox proportional hazards approach have been proposed to handle clustered or multiple event data. Of particular note are five Cox-based models for recurrent event data: Andersen and Gill (AG); Wei, Lin and Weissfeld (WLW); Prentice, Williams and Peterson, total time (PWP-CP) and gap time (PWP-GT); and Lee, Wei and Amato (LWA). Some authors have compared these models by observing differences that arise from fitting the models to real and simulated data. However, no attempt has been made to systematically identify the components of the models that are appropriate for recurrent event data. We propose a systematic way of characterizing such Cox-based models using four key components: risk intervals; baseline hazard; risk set, and correlation adjustment. From the definitions of risk interval and risk set there are conceptually seven such Cox-based models that are permissible, five of which are those previously identified. The two new variant models are termed the 'total time - restricted' (TT-R) and 'gap time - unrestricted' (GT-UR) models. The aim of the paper is to determine which models are appropriate for recurrent event data using the key components. The models are fitted to simulated data sets and to a data set of childhood recurrent infectious diseases. The LWA model is not appropriate for recurrent event data because it allows a subject to be at risk several times for the same event. The WLW model overestimates treatment effect and is not recommended. We conclude that PWP-GT and TT-R are useful models for analysing recurrent event data, providing answers to slightly different research questions. Further, applying a robust variance to any of these models does not adequately account for within-subject correlation.
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Affiliation(s)
- P J Kelly
- Centre for Clinical Epidemiology and Biostatistics, The University of Newcastle, Level 3, David Maddison Building, Royal Newcastle Hospital, Newcastle, NSW, 2300, Australia.
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Abstract
OBJECTIVE As conflicting studies have recently been published, we aimed to determine if Helicobacter pylori (H. pylori) infection is associated with gastric adenocarcinoma. METHODS This was a meta-analysis of observational epidemiological studies. RESULTS A total of 42 studies met the selection criteria and were categorized by the type of study design: eight cohort and 34 case-control studies. The pooled odds ratio for H. pylori in relation to gastric carcinoma was 2.04 (95% CI: 1.69-2.45). Both patient age (OR 0.77, 95% CI: 0.68-0.89) and intestinal type cancers (OR 1.14, 95% CI: 1.05-1.25) were independent effect modifiers. Analysis of other effect modifiers showed no relationship with female gender (OR 0.76, 95% CI: 0.64-0.89), stage of cancer (advanced %) (OR 1.12, 95% CI: 0.88-1.43), anatomical location (cardia %) (OR 1.54, 95% CI: 0.32-7.39) or cohort (nested case-control) studies (OR 1.72, 95% CI: 0.32-9.17). There was significant heterogeneity among the studies (tau2 = 149; p < 0.001). The quality of the studies varied considerably, with the majority of excellent studies producing positive results and the very poor to moderate studies producing mixed results. CONCLUSIONS H. pylori infection is associated with a 2-fold increased risk of developing gastric adenocarcinoma.
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Affiliation(s)
- G D Eslick
- Centre for Clinical Epidemiology and Biostatistics, Royal Newcastle Hospital, The University of Newcastle, Australia
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Abstract
OBJECTIVE As conflicting studies have recently been published, we aimed to determine if Helicobacter pylori (H. pylori) infection is associated with gastric adenocarcinoma. METHODS This was a meta-analysis of observational epidemiological studies. RESULTS A total of 42 studies met the selection criteria and were categorized by the type of study design: eight cohort and 34 case-control studies. The pooled odds ratio for H. pylori in relation to gastric carcinoma was 2.04 (95% CI: 1.69-2.45). Both patient age (OR 0.77, 95% CI: 0.68-0.89) and intestinal type cancers (OR 1.14, 95% CI: 1.05-1.25) were independent effect modifiers. Analysis of other effect modifiers showed no relationship with female gender (OR 0.76, 95% CI: 0.64-0.89), stage of cancer (advanced %) (OR 1.12, 95% CI: 0.88-1.43), anatomical location (cardia %) (OR 1.54, 95% CI: 0.32-7.39) or cohort (nested case-control) studies (OR 1.72, 95% CI: 0.32-9.17). There was significant heterogeneity among the studies (tau2 = 149; p < 0.001). The quality of the studies varied considerably, with the majority of excellent studies producing positive results and the very poor to moderate studies producing mixed results. CONCLUSIONS H. pylori infection is associated with a 2-fold increased risk of developing gastric adenocarcinoma.
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Affiliation(s)
- G D Eslick
- Centre for Clinical Epidemiology and Biostatistics, Royal Newcastle Hospital, The University of Newcastle, Australia
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39
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Abstract
The objective of this study was to validate the SF-12 Health Survey in heart and stroke patients using a community-based study. Between November 1995 and August 1996, 3,362 patients were invited to join the Hunter Heart and Stroke Register in New South Wales, Australia and to complete the SF-12 Health Survey. Of the 3,362 patients, 2,341 (70%) returned the SF-12. Of those 2,341 patients, 78% completed all 12 items. Those who did not complete the questionnaire were significantly more likely to be females, older, less educated, have stayed longer in hospital and been admitted on emergency. The SF-12 demonstrated construct validity in an analysis restricted to the 1,831 patients who completed the questionnaire: scores measuring physical and mental health status were statistically significantly higher in men than women, in younger than older, in those who had shorter than longer lengths of stay in hospital, in patients whose hospital admissions were planned than emergencies and in heart than stroke patients. Construct validity of the SF-12 among patients able to complete the SF-12 suggests considerable potential for its use in assessing health status in large-scale surveys. However, caution should be taken with the heart and stroke population because of a relatively high in completion rate.
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Affiliation(s)
- L L Lim
- Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, Australia.
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40
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Lim LL, O'Connell RL, Heller RF. Differences in management of heart attack patients between metropolitan and regional hospitals in the Hunter Region of Australia. Aust N Z J Public Health 1999; 23:61-6. [PMID: 10083691 DOI: 10.1111/j.1467-842x.1999.tb01206.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
OBJECTIVES To test the hypothesis that among patients with acute myocardial infarction (AMI) length of hospital stay, drug use in hospital and on discharge were different between metropolitan and regional hospitals after adjusting for differences in patient baseline risk. METHODS A retrospective cohort study using a community-based register of heart attack patients assessed 1,406 patients admitted for definite AMI to three metropolitan and five regional hospitals in the Lower Hunter Region of NSW, between January 1, 1990, and March 31, 1994. RESULTS Patients in metropolitan hospitals were significantly less likely to stay in hospital for more than seven days (adjusted odds ratio = 0.50; 95% CI 0.34-0.73), significantly more likely to receive ACE inhibitors (adj. OR = 1.47; 1.27-1.71) and less likely to receive calcium channel blocker (adj. OR = 0.70; 0.54-0.98). Regardless of disease severity, metropolitan hospitals had a higher percentage of patients for whom drugs shown to decrease mortality after AMI were used (streptokinase, aspirin, ACE inhibitor); a lower percentage of patients received drugs shown to have no benefit or even a detrimental effect (calcium channel blocker). Both groups had relatively low use of beta blocker, also shown to be of benefit. CONCLUSIONS Regional hospitals had longer hospital stays than metropolitan hospitals and less use of drugs of proven benefit.
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Affiliation(s)
- L L Lim
- Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, New South Wales.
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41
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Abstract
We examined the variation in stated practice in the management of acute myocardial infarction (AMI) among doctors in Australia, Brazil, Chile, India and Thailand. Hospitals were identified as primary, secondary or tertiary by investigators from around their own region. All doctors within each hospital who would be expected to treat patients with AMI were asked to indicate which investigations and treatments they would offer to a patient with an AMI who develops angina on Day 3 after admission. The numbers of hospitals ranged from 5 to 26 per country, and doctor response rates varied from 70 to 100%. Within-country variation was large, and statistically significant variations were seen between countries in the use of most interventions. The large variation both between and within a range of countries across the economic spectrum suggests a widespread need for agreement about what constitutes appropriate management after AMI.
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Affiliation(s)
- R F Heller
- Centre for Clinical Epidemiology and Biostatistics, The University of Newcastle, Faculty of Medicine and Health Sciences, NSW, Australia.
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42
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Abstract
We tested the hypothesis that low quality of life (QOL) after discharge from hospital with ischaemic heart disease (IHD) is associated with higher rates of later adverse outcomes (death and subsequent hospital admission for acute myocardial infarction or congestive cardiac failure). Three hundred and seventy-five patients previously enrolled in an intervention study which assessed QOL six months after hospitalisation were followed up for an additional 18 months. The rates of adverse outcomes increased as QOL decreased (high QOL 9%; moderate 18%; low 28%). After adjustment for known prognostic factors, the risk of an adverse outcome was still higher in 'low' and 'moderate' compared to 'high' QOL subjects (low QOL adjusted OR = 2.6, 95% CI = 1.2-5.8; moderate 1.9, 0.8-4.2). In conclusion, QOL after discharge from hospital appears to be an independent predictor of later morbidity and mortality.
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Affiliation(s)
- L L Lim
- Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, New South Wales.
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Lim LL, Tesfay GM, Heller RF. Management of patients with diabetes after heart attack: a population-based study of 1982 patients from a heart disease register. Aust N Z J Med 1998; 28:334-42. [PMID: 9673746 DOI: 10.1111/j.1445-5994.1998.tb01958.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Previous studies examining the management of patients with diabetes after acute myocardial infarction (AMI) have been based on clinical studies under experimental conditions. We used data from a population-based heart disease register to document differences in the management after AMI between patients with and without diabetes. HYPOTHESIS There were no differences in the prescription rates of aspirin, beta blockers, streptokinase, ACE inhibitors and calcium channel blockers between patients with and without diabetes admitted to hospital with AMI. METHODS A retrospective study of 268 patients with, and 1714 patients without, diabetes discharged from hospital with 'definite' AMI between August 1988 and March 1994. RESULTS The prescription rates of all five drug classes increased between 1988 and 1994 both for patients with and without diabetes. Patients with diabetes were significantly less likely to have been prescribed aspirin (76% vs 85%), beta blockers (41% vs 53%) and streptokinase (25% vs 43%) but more likely to have been prescribed ACE inhibitors (47% vs 29%) and calcium channel blockers (50% vs 40%). The differences in prescription rates were statistically significant after controlling for age, sex, history of ischaemic heart disease, smoking status, educational level and disease severity. CONCLUSION Patients with diabetes were less likely to have been prescribed three of the five drug classes where evidence points to a beneficial effect after AMI. Further work is needed to identify the reasons for the disparity between management of patients with and without diabetes, and to develop effective strategies to increase the implementation of best practice guidelines in the management of patients with diabetes after AMI.
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Affiliation(s)
- L L Lim
- Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, NSW
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Lim LL, Kinlay S, Fisher JD, Dobson AJ, Heller RF. Can ECG changes predict the long-term outcome in patients admitted to hospital for suspected acute myocardial infarction? Cardiology 1997; 88:460-7. [PMID: 9286509 DOI: 10.1159/000177377] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
7,028 patients with suspected acute myocardial infarction and discharged alive from hospital were followed in a 10-year community-based study. The long-term prognosis was relatively good if the electrocardiograms (ECGs) were normal (5-year all-cause death rate 5%), poor with uncodable ECGs showing rhythm or conduction disturbances (37%), and intermediate with new Q wave, new ST elevation, new T wave inversion or ischemic ECG (17-21%), and with new ST depression (27%). Similar patterns were found for ischemic cardiac death and reinfarction. The long-term prognosis of patients with suspected acute myocardial infarction is relatively good if the ECGs are normal and poor if ECGs are uncodable. ST depression may be a marker for a worse long-term outcome.
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Affiliation(s)
- L L Lim
- Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, N.S.W., Australia
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45
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Abstract
This study examined the reproducibility of data, not generally considered at risk for poor patient recall, obtained on two separate occasions. Our study used data collected for a register of heart attacks in the Lower Hunter Region of New South Wales, and included 1675 patients who were registered at least twice. Reporting inconsistencies between occasions were assessed for eight data items. We found that the sex of five patients had been recorded differently on the two occasions. Among patients interviewed on both occasions, between 0.5 per cent and 2.0 per cent of patients had inconsistent reports for marital status, country of birth, smoking status and height, 2.7 per cent for date of birth, 13 per cent for education level and between 1.6 per cent and 9.6 per cent for the history of various medical conditions. Patients not from an English-speaking background, over 60 years of age or without tertiary education tended to have higher rates of inconsistent reporting. Time between occasions, marital status and sex were not associated with increased rates of inconsistent reporting. We concluded that apparently straightforward data items, such as date of birth and education level, were not perfectly reproducible when obtained by patient interview on separate occasions. Our results provide a starting point for sensitivity analysis in other studies if the potential inaccuracies in reporting of such data should be of concern.
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Affiliation(s)
- L L Lim
- Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, NSW.
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46
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Henry D, Lim LL, Garcia Rodriguez LA, Perez Gutthann S, Carson JL, Griffin M, Savage R, Logan R, Moride Y, Hawkey C, Hill S, Fries JT. Variability in risk of gastrointestinal complications with individual non-steroidal anti-inflammatory drugs: results of a collaborative meta-analysis. BMJ 1996; 312:1563-6. [PMID: 8664664 PMCID: PMC2351326 DOI: 10.1136/bmj.312.7046.1563] [Citation(s) in RCA: 504] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVE To compare the relative risks of serious gastrointestinal complications reported with individual non-steroidal anti-inflammatory drugs. DESIGN Systematic review of controlled epidemiological studies that found a relation between use of the drugs and admission to hospital for haemorrhage or perforation. SETTING Hospital and community based case-control and cohort studies. MAIN OUTCOME MEASURES (a) Estimated relative risks of gastrointestinal complications with use of individual drugs, exposure to ibuprofen being used as reference; (b) a ranking that best summarised the sequence of relative risks observed in the studies. RESULTS 12 studies met the inclusion criteria. 11 provided comparative data on ibuprofen and other drugs. Ibuprofen ranked lowest or equal lowest for risk in 10 of the 11 studies. Pooled relative risks calculated with exposure to ibuprofen used as reference were all significantly greater than 1.0 (interval of point estimates 1.6 to 9.2). Overall, ibuprofen was associated with the lowest relative risk, followed by diclofenac. Azapropazone, tolmetin, ketoprofen, and piroxicam ranked highest for risk and indomethacin, naproxen, sulindac, and aspirin occupied intermediate positions. Higher doses of ibuprofen were associated with relative risks similar to those with naproxen and indomethacin. CONCLUSIONS The low risk of serious gastrointestinal complications with ibuprofen seems to be attributable mainly to the low doses of the drug used in clinical practice. In higher doses ibuprofen is associated with a similar risk to other non-steroidal anti-inflammatory drugs. Use of low risk drugs in low dosage as first line treatment would substantially reduce the morbidity and mortality due to serious gastrointestinal toxicity from these drugs.
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Affiliation(s)
- D Henry
- Centre for Clinical Epidemiology and Biostatistics, Faculty of Medicine and Health Sciences, University of Newcastle, New South Wales, Australia.
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Lim LL, Valenti LA, Knapp JC, Dobson AJ, Plotnikoff R, Higginbotham N, Heller RF. A self-administered quality-of-life questionnaire after acute myocardial infarction. J Clin Epidemiol 1993; 46:1249-56. [PMID: 8229102 DOI: 10.1016/0895-4356(93)90089-j] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A slightly modified version of the Quality-of-Life after Myocardial Infarction (QLMI) questionnaire developed by Oldridge and colleagues was applied in a self-administered mode to patients with suspected acute myocardial infarction (AMI) in a randomized controlled trial of secondary prevention. Acceptability of the questionnaire was good, with 93% of responders answering all items. Factor analysis suggested three quality-of-life (QL) dimensions which we called "emotional", "physical" and "social". These differed somewhat from the dimensions proposed by Oldridge and colleagues. However, a sensitivity analysis showed relative invariance of results to weighting schemes. Scores on our three dimensions were responsive to differences between the treatment groups, and demonstrated construct validity based on associations between the measured QL and variables expected to affect QL. We conclude that the QLMI questionnaire has good potential as an instrument for assessing QL in post-AMI patients and that it can be successfully self-administered.
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Affiliation(s)
- L L Lim
- Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, NSW, Australia
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48
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Lim LL. Estimating compliance to study medication from serum drug levels: application to an AIDS clinical trial of zidovudine. Biometrics 1992; 48:619-30. [PMID: 1637984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This paper examines the use of serum drug levels to assess compliance to study medication in a clinical trial. We discuss problems of false-positivity, false-negativity, and bias that arise because of experimental errors in the drug assays, pharmacokinetic variations of the drug, and differential dosing levels. Basic concepts in probability are applied to derive a simple model that quantifies these problems. This model is used to obtain an estimate of compliance rate that corrects for these problems. However, derivation of this estimate requires additional information about false-positive and false-negative rates of the assay as well as some knowledge of the pharmacokinetic properties of the drug. We illustrate the evaluation of such a compliance estimate in the setting of an AIDS clinical trial of zidovudine (ZDV), in which some accessory data are available on the properties of ZDV serum assays and on the pharmacokinetic behavior of ZDV. We also describe a method that uses the accessory data to provide the additional information needed for computing the compliance estimate.
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Affiliation(s)
- L L Lim
- Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts 02115
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Lim LL, Whitehead J. Estimating the ventilation-perfusion distribution: an ill-posed integral equation problem. Biometrics 1992; 48:175-87. [PMID: 1316180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The distribution of ventilation-perfusion ratio over the lung is a useful indicator of the efficiency of lung function. Information about this distribution can be obtained by observing the retention in blood of inert gases passed through the lung. These retentions are related to the ventilation-perfusion distribution through an ill-posed integral equation. An unusual feature of this problem of estimating the ventilation-perfusion distribution is the small amount of data available; typically there are just six data points, as only six gases are used in the experiment. A nonparametric smoothing method is compared to a simpler method that models the distribution as a histogram with five classes. Results from the smoothing method are found to be very unstable. In contrast, the simpler method gives stable solutions with parameters that are physiologically meaningful. It is concluded that while such smoothing methods may be useful for solving some ill-posed integral equation problems, the simpler method is preferable when data are scarce.
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Affiliation(s)
- L L Lim
- Department of Applied Statistics, University of Reading, United Kingdom
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50
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Krogstad DJ, Eveland MR, Lim LL, Volberding PA, Sadler BM. Drug level monitoring in a double-blind multicenter trial: false-positive zidovudine measurements in AIDS clinical trials group protocol 019. Antimicrob Agents Chemother 1991; 35:1160-4. [PMID: 1929258 PMCID: PMC284304 DOI: 10.1128/aac.35.6.1160] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Twenty-three different laboratories using four different assay methods reported zidovudine (ZDV; azidothymidine) measurements in a double-blind trial of ZDV for asymptomatic human immunodeficiency virus-infected patients (AIDS Clinical Trials Group Protocol 019). The risk of false-positive ZDV measurements was defined with coded specimens containing no ZDV in a quality control testing program. This testing identified six problem laboratories which reported ZDV levels of greater than or equal to 100 ng/ml for specimens with no ZDV; all of these laboratories used high-performance liquid chromatography. These six laboratories reported a disproportionately high fraction of positive assays for subjects randomized to the placebo group (31% for these 6 laboratories versus 4% for the other 17 laboratories; P less than 0.0001). The high number of false-positive ZDV results reported by these six laboratories suggested that many of the positive results that they reported for patient specimens were also false-positive results. This hypothesis was examined by retesting specimens from patients in the placebo group that had been reported as positive by these laboratories. Ninety percent (19 of 21) of these specimens were negative on retesting at the reference laboratory. These results confirm the hypothesis; they demonstrate the need for quality control testing to avoid the misinterpretation of multicenter trials because of incorrect laboratory data.
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Affiliation(s)
- D J Krogstad
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
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