Developing high intensity ultrasonic cleaning (HIUC) for post-processing additively manufactured metal components

The high energy phenomenon of cavitation bubble collapses has enabled numerous applications, including cleaning. In ultrasonic cleaning, cavitation intensity is typically lower than in other applications, such as sonochemistry and material processing. However, there has been an emerging application in intense cleaning of metal additively manufactured (AM) components. The presence of partially melted powders on AM surfaces is undesirable, contributing to high surface roughness and posing contamination risks during usage. We designed a high-intensity cavitation cleaning process that has significantly higher inertial cavitation intensity - i.e., erosion potential - than a conventional ultrasonic cleaning tank. Through acoustic signal characterisation, we showed that placing transducer sets on four sides of the tank could effectively focus and generate high-amplitude pressure waves directed towards the central region. Strong subharmonic signals indicate intensely inertial cavitation throughout the tank. Cavitation intensities were measured at various locations to understand the wave transmission characteristics and distribution patterns. Our results show that the cavitation intensity distribution is highly dependent on the height position. Finally, we demonstrated that the high intensity ultrasonic cleaning (HIUC) process could remove partially melted powders from an AM surface - which was not possible through conventional ultrasonic cleaning. HIUC could lead to higher cleaning efficiency and enhanced AM specimen cleanliness.

Spatial Methods for Inferring Extremes in Dengue Outbreak Risk in Singapore

Dengue is a major vector-borne disease worldwide. Here, we examined the spatial distribution of extreme weekly dengue outbreak risk in Singapore from 2007 to 2020. We divided Singapore into equal-sized hexagons with a circumradius of 165 m and obtained the weekly number of dengue cases and the surface characteristics of each hexagon. We accounted for spatial heterogeneity using max-stable processes. The 5-, 10-, 20-, and 30-year return levels, or the weekly dengue case counts expected to be exceeded once every 5, 10, 20, and 30 years, respectively, were determined for each hexagon conditional on their surface characteristics remaining constant over time. The return levels were higher in the country's east, with the maximum weekly dengue cases per hexagon expected to exceed 51 at least once in 30 years in many areas. The surface characteristics with the largest impact on outbreak risk were the age of public apartments and the percentage of impervious surfaces, where a 3-year and 10% increase in each characteristic resulted in a 3.8% and 3.3% increase in risk, respectively. Vector control efforts should be prioritized in older residential estates and places with large contiguous masses of built-up environments. Our findings indicate the likely scale of outbreaks in the long term.

Strategies to Mitigate Establishment Using the Wolbachia Incompatible Insect Technique

The Incompatible Insect Technique (IIT) strategy involves the release of male mosquitoes infected with the bacterium Wolbachia. Regular releases of male Wolbachia-infected mosquitoes can lead to the suppression of mosquito populations, thereby reducing the risk of transmission of vector-borne diseases such as dengue. However, due to imperfect sex-sorting under IIT, fertile Wolbachia-infected female mosquitoes may potentially be unintentionally released into the environment, which may result in replacement and failure to suppress the mosquito populations. As such, mitigating Wolbachia establishment requires a combination of IIT with other strategies. We introduced a simple compartmental model to simulate ex-ante mosquito population dynamics subjected to a Wolbachia-IIT programme. In silico, we explored the risk of replacement, and strategies that could mitigate the establishment of the released Wolbachia strain in the mosquito population. Our results suggest that mitigation may be achieved through the application of a sterile insect technique. Our simulations indicate that these interventions do not override the intended wild type suppression of the IIT approach. These findings will inform policy makers of possible ways to mitigate the potential establishment of Wolbachia using the IIT population control strategy.

Fine-scale estimation of effective reproduction numbers for dengue surveillance

The effective reproduction number R_t is an epidemiological quantity that provides an instantaneous measure of transmission potential of an infectious disease. While dengue is an increasingly important vector-borne disease, few have used R_t as a measure to inform public health operations and policy for dengue. This study demonstrates the utility of R_t for real time dengue surveillance. Using nationally representative, geo-located dengue case data from Singapore over 2010–2020, we estimated R_t by modifying methods from Bayesian (EpiEstim) and filtering (EpiFilter) approaches, at both the national and local levels. We conducted model assessment of R_t from each proposed method and determined exogenous temporal and spatial drivers for R_t in relation to a wide range of environmental and anthropogenic factors. At the national level, both methods achieved satisfactory model performance (R²_EpiEstim = 0.95, R²_EpiFilter = 0.97), but disparities in performance were large at finer spatial scales when case counts are low (MASE _EpiEstim = 1.23, MASE_EpiFilter = 0.59). Impervious surfaces and vegetation with structure dominated by human management (without tree canopy) were positively associated with increased transmission intensity. Vegetation with structure dominated by human management (with tree canopy), on the other hand, was associated with lower dengue transmission intensity. We showed that dengue outbreaks were preceded by sustained periods of high transmissibility, demonstrating the potential of R_t as a dengue surveillance tool for detecting large rises in dengue cases. Real time estimation of R_t at the fine scale can assist public health agencies in identifying high transmission risk areas and facilitating localised outbreak preparedness and response.

The effective reproduction number R_t is an epidemiological quantity that provides an instantaneous measure of transmission potential of an infectious disease. While dengue is an increasingly important vector-borne disease, few have used R_t as a measure to inform public health operations and policy for dengue. This study demonstrates the utility of R_t for real time dengue surveillance. Using nationally representative, geo-located dengue case data from Singapore over 2010–2020, we estimated R_t by modifying methods from Bayesian (EpiEstim) and filtering (EpiFilter) approaches, at both the national and local levels. We conducted model assessment of R_t from each proposed method and determined exogenous temporal and spatial drivers for R_t in relation to a wide range of environmental and anthropogenic factors. At the national level, both methods achieved high accuracy, but disparities in performance were large at finer spatial scales when case counts are low. This study demonstrates the potential of R_t as a dengue surveillance tool for detecting large rises in dengue cases. Real time estimation of R_t at the fine scale can assist public health agencies in identifying high transmission risk areas and facilitating localised outbreak preparedness and response.

Testing strategies to contain COVID-19 in migrant worker dormitories

Introduction

COVID-19 transmission within overcrowded migrant worker dormitories is an ongoing global issue. Many countries have implemented extensive control measures to prevent the entire migrant worker population from becoming infected. Here, we explore case count outcomes when utilizing lockdown and testing under different testing measures and transmissibility settings.

Methods

We built a mathematical model which estimates transmission across 10 different blocks with 1000 individuals per block under different parameter combinations and testing conditions over the period of 1 month. We vary parameters including differences in block connectivity, underlying recovered proportions at the time of intervention, case importation rates and testing protocols using either PCR or rapid antigen testing.

Results

We estimate that a relatively transmissible environment with fortnightly PCR testing at a relatively low initial recovered proportion of 40%, low connectivity where 10% of contacts occurred outside of the infected individuals’ block and a high importation rate of 1100000 per day, results in an average of 39 (95%Interval: 9–121) new COVID-19 cases after one month of observation. Similar results were observed for weekly rapid antigen testing at 33 (9–95) cases.

Interpretation

Our findings support the need for either fortnightly PCR testing or weekly rapid antigen testing in high population density environments such as migrant worker dormitories. Repeated mass testing is highly effective, preventing localized site outbreaks and reducing the need for site wide lockdowns or other extensive social distancing measures within and outside of dormitories.

Hyperendemicity associated with increased dengue burden

Over 105 million dengue infections are estimated to occur annually. Understanding the disease dynamics of dengue is often difficult due to multiple strains circulating within a population. Interactions between dengue serotype dynamics may result in complex cross-immunity dynamics at the population level and create difficulties in terms of formulating intervention strategies for the disease. In this study, a nationally representative 16-year time series with over 43 000 serotyped dengue infections was used to infer the long-run effects of between and within strain interactions and their impacts on past outbreaks. We used a novel identification strategy incorporating sign-identified Bayesian vector autoregressions, using structural impulse responses, historical decompositions and counterfactual analysis to conduct inference on dengue dynamics post-estimation. We found that on the population level: (i) across-serotype interactions on the population level were highly persistent, with a one time increase in any other serotype associated with long run decreases in the serotype of interest (range: 0.5–2.5 years) and (ii) over 38.7% of dengue cases of any serotype were associated with across-serotype interactions. The findings in this paper will substantially impact public health policy interventions with respect to dengue.

From the 20th to the 21st century: the first 100 years of paediatrics in Singapore

In Singapore, paediatrics as a separate discipline was started in 1921 at Singapore General Hospital (SGH). From Mistri Wing to Alexandra Hospital (AH) and Tan Tock Seng Hospital (TTSH), paediatrics was started at National University Hospital (NUH) and the Children’s Hospital at KK Women’s and Children’s Hospital (KKH) from 1997. After World War II, neonatology started in KKH, followed by Toa Payoh Hospital (TPH), AH, NUH and SGH. Neonates from TPH and AH were moved to KKH in 1990. Our pioneering giants include Dr Gopal Haridas, Professors Wong Hock Boon (First Paediatrics Professor), Tan Cheng Lim and Tan Kim Leong. Paediatrics in Singapore is resplendent with many achievements. Prof Wong identified the relationship of hyperbilirubinaemia/kernicterus with glucose-6-phosphate dehydrogenase (G6PD) deficiency and initiated G6PD deficiency screening. This has saved many lives and improved the overall health of children in Singapore. 100 years on, we stand firmly on the shoulders of our pioneering clinician giants as we face the paediatric millennial health needs of this new century.

Dynamic dengue haemorrhagic fever calculators as clinical decision support tools in adult dengue

BACKGROUND

The objective of this study was to develop multiple prediction tools that calculate the risk of developing dengue haemorrhagic fever.

METHODS

Training data consisted of 1771 individuals from 2006-2008 admitted with dengue fever whereby 304 developed dengue haemorrhagic fever during hospitalisation. Least absolute shrinkage and selection operator regression was used to construct three types of calculators, static admission calculators and dynamic calculators that predict the risk of developing dengue haemorrhagic fever for a subsequent day (DAily Risk Tomorrow [DART]) or for any future point after a specific day since fever onset (DAily Risk Ever [DARE]).

RESULTS

From 119 admission covariates, 35 were in at least one of the calculators, which reported area under the curve (AUC) values of at least 0.72. Addition of person-time data for DART improved AUC to 0.76. DARE calculators displayed a large increase in AUC to 0.79 past day 7 with the inclusion of a strong predictor, maximum temperature on day 6 since onset, indicative of a saddleback fever.

CONCLUSIONS

All calculators performed well when validated with 2005 data. Addition of daily variables further improved the accuracy. These calculators can be used in tandem to assess the risk of dengue haemorrhagic fever upon admission and updated daily to obtain more precise risk estimates.

Estimating direct and spill-over impacts of political elections on COVID-19 transmission using synthetic control methods

Mass gathering events have been identified as high-risk environments for community transmission of coronavirus disease 2019 (COVID-19). Empirical estimates of their direct and spill-over effects however remain challenging to identify. In this study, we propose the use of a novel synthetic control framework to obtain causal estimates for direct and spill-over impacts of these events. The Sabah state elections in Malaysia were used as an example for our proposed methodology and we investigate the event's spatial and temporal impacts on COVID-19 transmission. Results indicate an estimated (i) 70.0% of COVID-19 case counts within Sabah post-state election were attributable to the election's direct effect; (ii) 64.4% of COVID-19 cases in the rest of Malaysia post-state election were attributable to the election's spill-over effects. Sensitivity analysis was further conducted by examining epidemiological pre-trends, surveillance efforts, varying synthetic control matching characteristics and spill-over specifications. We demonstrate that our estimates are not due to pre-existing epidemiological trends, surveillance efforts, and/or preventive policies. These estimates highlight the potential of mass gatherings in one region to spill-over into an outbreak of national scale. Relaxations of mass gathering restrictions must therefore be carefully considered, even in the context of low community transmission and enforcement of safe distancing guidelines.

Economic impact of dengue in Singapore from 2010 to 2020 and the cost-effectiveness of Wolbachia interventions

The release of Wolbachia-infected mosquitoes is a promising disease intervention strategy that aims to control dengue and other arboviral infections. While early field trials and modelling studies suggest promising epidemiological and entomological outcomes, the overall cost effectiveness of the technology is not well studied in a resource rich setting nor under the suppression approach that aims to suppress the wild-type mosquito population through the release of Wolbachia-infected males. We used economical and epidemiological data from 2010 to 2020 to first ascertain the economic and health costs of dengue in Singapore, a high income nation where dengue is hyper-endemic. The hypothetical cost effectiveness of a national Wolbachia suppression program was then evaluated historically from 2010 to 2020. We estimated that the average economic impact of dengue in Singapore from 2010 to 2020 in constant 2010US$ ranged from $1.014 to $2.265 Billion. Using empirically derived disability weights, we estimated a disease burden of 7,645-21,262 DALYs from 2010-2020. Under an assumed steady-state running cost of a national Wolbachia suppression program in Singapore, we conservatively estimate that Wolbachia would cost an estimated $50,453-$100,907 per DALYs averted and would lead to an estimated $329.40 Million saved in economic costs over 2010 to 2020 under 40% intervention efficacy. Wolbachia releases in Singapore are expected to be highly cost-effective and its rollout must be prioritised to reduce the onward spread of dengue.

Ethnicity, Neighborhood and Individual Socioeconomic Status, and Obesity: The Singapore Multiethnic Cohort

OBJECTIVE

It remains unclear whether ethnicity has an impact on obesity independent of socioeconomic status (SES) and environmental factors. Singapore provides a unique opportunity to address this issue because three major Asian ethnic groups are represented, and government policies prevent ethnic segregation. Therefore this study examined associations between ethnicity, SES, and obesity within neighborhoods in Singapore.

METHODS

Cross-sectional data from 29,819 participants of the Singapore Multiethnic Cohort who were aged 21 to 75 years and of Chinese, Malay, and Indian ethnicity were used. Obesity was defined using Asian criteria. Multilevel models used obesity as the dependent variable and age, marital status, ethnicity, education level, income, and neighborhood SES as independent variables.

RESULTS

Education level was more strongly inversely associated with obesity than income level or neighborhood SES. The association between ethnicity and obesity was not substantially explained by measures of individual and neighborhood SES. In females, the fully adjusted odds ratio of obesity was 5.01 for Malay ethnicity and 4.81 for Indian ethnicity as compared with Chinese ethnicity. In males, these odds ratios were 2.61 and 2.07, respectively.

CONCLUSIONS

Ethnicity was strongly associated with obesity independent of SES and neighborhood environment. More research on sociocultural factors contributing to ethnic differences in obesity is warranted.

Projected burden of type 2 diabetes mellitus-related complications in Singapore until 2050: a Bayesian evidence synthesis

OBJECTIVE

We examined the effects of age, gender, and ethnicity on the risk of acute myocardial infarction, stroke, and end-stage renal disease according to type 2 diabetes mellitus status among adults aged 40-79 in Singapore.

METHODS

A Bayesian inference framework was used to derive age-specific, gender-specific and ethnicity-specific prevalence of type 2 diabetes mellitus from the 2010 Singapore National Health Survey, and age-standardized gender and ethnicity-specific incidence rates of acute myocardial infarction, stroke and end-stage renal disease from the National Registry of Diseases Office. Population forecasts were used in tandem with incidence rates to project the future chronic disease burden until 2050.

RESULTS

The highest relative risk of acute myocardial infarction was observed in the youngest age group (aged 40-44), with higher relative risk for women (men: 4.3 (2.7-6.4); women: 16.9 (9.3-28.3)). A similar trend was observed for stroke (men: 6.5 (4.2-9.7); women: 10.7 (6.0-17.4)). For end-stage renal disease, the highest relative risk was for men aged 45-50 (11.8 (8.0-16.9)) and women aged 55-60 (16.4 (10.7-24.0)). The annual incidence of acute myocardial infarction is projected to rise from 9300 (in 2019) to 16 400 (in 2050), the number of strokes from 7300 to 12 800, and the number of end-stage renal disease cases from 1700 to 2700.

CONCLUSIONS

Type 2 diabetes mellitus was associated with an increased risk of complications and is modulated by age and gender. Prevention and early detection of type 2 diabetes mellitus can reduce the increasing burden of secondary complications.

Incidence of breast cancer attributable to breast density, modifiable and non-modifiable breast cancer risk factors in Singapore

Incidence of breast cancer is rising rapidly in Asia. Some breast cancer risk factors are modifiable. We examined the impact of known breast cancer risk factors, including body mass index (BMI), reproductive and hormonal risk factors, and breast density on the incidence of breast cancer, in Singapore. The study population was a population-based prospective trial of screening mammography - Singapore Breast Cancer Screening Project. Population attributable risk and absolute risks of breast cancer due to various risk factors were calculated. Among 28,130 women, 474 women (1.7%) developed breast cancer. The population attributable risk was highest for ethnicity (49.4%) and lowest for family history of breast cancer (3.8%). The proportion of breast cancers that is attributable to modifiable risk factor BMI was 16.2%. The proportion of breast cancers that is attributable to reproductive risk factors were low; 9.2% for age at menarche and 4.2% for number of live births. Up to 45.9% of all breast cancers could be avoided if all women had breast density <12% and BMI <25 kg/m². Notably, sixty percent of women with the lowest risk based on non-modifiable risk factors will never reach the risk level recommended for mammography screening. A combination of easily assessable breast cancer risk factors can help to identify women at high risk of developing breast cancer for targeted screening. A large number of high-risk women could benefit from risk-reduction and risk stratification strategies.

Evaluating smoking control policies in the e-cigarette era: a modelling study

Background

In jurisdictions in which electronic cigarettes are currently prohibited, policy makers must weigh the potentially lower risk compared with conventional cigarettes against the risk of initiation of e-cigarettes among non-smokers.

Methods

We simulated a synthetic population over a 50-year time horizon with an open cohort model using data from Singapore, a country where e-cigarettes are currently prohibited, and data from the USA, the UK and Japan. Using the smoking prevalence and the quality-adjusted life year gained calculated, we compared tobacco control policies without e-cigarettes—namely, raising the minimum legal age (MLA), introducing a smoke-free generation (SFG) and tax rises on tobacco consumption—with policies legalising e-cigarettes, either taking a laissez-faire approach or under some form of restriction. We also evaluated combinations of these policies.

Results

Regardless of the country informing the transition probabilities to and from e-cigarette use in Singapore, a laissez-faire e-cigarette policy could reduce the smoking prevalence in the short term, but it is not as effective as other policies in the long term. The most effective single policies evaluated were SFG and aggressive tax rises; the most effective combination of policies considered was MLA plus moderate tax rises and e-cigarettes on prescription.

Conclusion

Policy makers in jurisdictions in which e-cigarettes are not yet established may be advised not to prioritise e-cigarettes in their tobacco end-game strategy, unless their use can be restricted to current smokers seeking to quit.

Surface Accessibility and Dynamics of Macromolecular Assemblies Probed by Covalent Labeling Mass Spectrometry and Integrative Modeling

Mass spectrometry (MS) has become an indispensable tool for investigating the architectures and dynamics of macromolecular assemblies. Here we show that covalent labeling of solvent accessible residues followed by their MS-based identification yields modeling restraints that allow mapping the location and orientation of subunits within protein assemblies. Together with complementary restraints derived from cross-linking and native MS, we built native-like models of four heterocomplexes with known subunit structures and compared them with available X-ray crystal structures. The results demonstrated that covalent labeling followed by MS markedly increased the predictive power of the integrative modeling strategy enabling more accurate protein assembly models. We applied this strategy to the F-type ATP synthase from spinach chloroplasts (cATPase) providing a structural basis for its function as a nanomotor. By subjecting the models generated by our restraint-based strategy to molecular dynamics (MD) simulations, we revealed the conformational states of the peripheral stalk and assigned flexible regions in the enzyme. Our strategy can readily incorporate complementary chemical labeling strategies and we anticipate that it will be applicable to many other systems providing new insights into the structure and function of protein complexes.

Vitamin D levels in 87 Asian patients with cutaneous lupus erythematosus: a case-control study

BACKGROUND

Cutaneous lupus erythematosus (CLE) is an autoimmune disease, often exacerbated by sun exposure. Patients are encouraged to avoid sun exposure, therefore predisposing them to vitamin D deficiency.

AIM

To investigate the prevalence of and risk factors for vitamin D deficiency in patients with CLE.

METHODS

Total serum 25-hydroxy vitamin D (25(OH)D) was measured in 87 consecutive patients with CLE and in 79 controls. Clinical characteristics, disease severity, medications used and lifestyle factors were analysed and compared to determine risk factors for inadequate (25(OH)D), defined as a serum (25(OH)D) level of < 20 μg/L.

RESULTS

We found that 51% (n = 44) of the patients with CLE had 25(OH)D levels of < 20 μg/L compared with 73% (n = 58) of the controls (P < 0.01). No significant differences in (25(OH)D) levels were found between cases and controls with regard to age, sex, ethnicity, smoking, sun exposure, sunblock use or vitamin D supplementation. Treatment with antimalarials showed a statistically significant association with lower vitamin D levels.

CONCLUSION

Low levels of vitamin D were found in both patients with CLE and controls. Despite being on vitamin D supplementation and living in an equatorial location, our Asian patients with CLE still had low levels of vitamin D. It is therefore important to ensure adequate vitamin D supplementation in patients with CLE, especially for those who are on antimalarial therapy.

Evaluation of carbon-based nanosorbents synthesised by ethylene decomposition on stainless steel substrates as potential sequestrating materials for nickel ions in aqueous solution

The present work covers the preparation of carbon-based nanosorbents by ethylene decomposition on stainless steel mesh without the use of external catalyst for the treatment of water containing nickel ions (Ni2+). The reaction temperature was varied from 650 to 850 degrees C, while reaction time and ethylene to nitrogen flow ratio were maintained at 30 min and 1:1 cm3/min, respectively. Results show that nanosorbents synthesised at a reaction temperature of 650 degrees C had the smallest average diameter (75 nm), largest BET surface area (68.95 m2/g) and least amount of impurity (0.98 wt.% Fe). A series of batch-sorption tests were performed to evaluate the effects of initial pH, initial metal concentration and contact time on Ni2+ removal by the nanosorbents. The equilibrium data fitted well to Freundlich isotherm. The kinetic data were best correlated to a pseudo second-order model indicating that the process was of chemisorption type. Further analysis by the Boyd kinetic model revealed that boundary layer diffusion was the controlling step. This primary study suggests that the prepared material with Freundlich constants compared well with those in the literature, is a promising sorbent for the sequestration of Ni2+ in aqueous solutions.

Sidewall oxide effects on spin-torque- and magnetic-field-induced reversal characteristics of thin-film nanomagnets

The successful operation of spin-based data storage devices depends on thermally stable magnetic bits. At the same time, the data-processing speeds required by today's technology necessitate ultrafast switching in storage devices. Achieving both thermal stability and fast switching requires controlling the effective damping in magnetic nanoparticles. By carrying out a surface chemical analysis, we show that through exposure to ambient oxygen during processing, a nanomagnet can develop an antiferromagnetic sidewall oxide layer that has detrimental effects, which include a reduction in the thermal stability at room temperature and anomalously high magnetic damping at low temperatures. The in situ deposition of a thin Al metal layer, oxidized to completion in air, greatly reduces or eliminates these problems. This implies that the effective damping and the thermal stability of a nanomagnet can be tuned, leading to a variety of potential applications in spintronic devices such as spin-torque oscillators and patterned media.

Optimising management in Turner syndrome: from infancy to adult transfer

Turner syndrome can be defined as loss or abnormality of the second X chromosome in at least one cell line in a phenotypic female. The condition occurs in approximately 1 in every 2000 live female births,(1) so that in the UK the prevalence for any year of life is in the region of 200 girls. The condition is much more common in utero, it being estimated that 1-2% of all conceptuses are affected, of whom only 1% will survive to term.

Angiotensin-I converting enzyme insertion/deletion polymorphism and its association with diabetic nephropathy: a meta-analysis of studies reported between 1994 and 2004 and comprising 14,727 subjects

AIMS/HYPOTHESIS

The ACE insertion/deletion polymorphism has been examined for association with diabetic nephropathy over the past decade with conflicting results. To clarify this situation, we conducted a comprehensive meta-analysis encompassing all relevant studies that were published between 1994 and 2004 and investigated this potential genetic association.

METHODS

A total of 14,727 subjects from 47 studies was included in this meta-analysis. Cases (n=8,663) were type 1 or 2 diabetic subjects with incipient (microalbuminuria) or advanced diabetic nephropathy (proteinuria, chronic renal failure, end-stage renal disease). Control subjects (n=6,064) were predominantly normoalbuminuric.

RESULTS

No obvious publication bias was detected. Using a minimal-case definition based on incipient diabetic nephropathy, subjects with the II genotype had a 22% lower risk of diabetic nephropathy than carriers of the D allele (pooled odds ratio [OR]=0.78, 95% CI=0.69-0.88). While there was a reduced risk of diabetic nephropathy associated with the II genotype among Caucasians with either type 1 or type 2 diabetes, the association was most marked among type 2 diabetic Asians (Chinese, Japanese, Koreans) (OR=0.65, 95% CI=0. 51-0.83). This OR is significantly different from the OR of 0.90 (95% CI= 0.78-1.04) that was obtained for type 2 diabetic Caucasians (p=0.019). Using a stricter case definition based on advanced diabetic nephropathy, a comparable risk reduction of 24-32% was observed among the three subgroups, although statistical significance was reached only among Asians.

CONCLUSIONS/INTERPRETATION

The results of our meta-analysis support a genetic association of the ACE Ins/Del polymorphism with diabetic nephropathy. These findings may have implications for the management of diabetic nephropathy using ACE inhibitors especially among type 2 diabetic Asians.

A randomized trial of amifostine as a cytoprotectant for patients receiving myeloablative therapy for allogeneic hematopoietic stem cell transplantation

We initiated a randomized study of amifostine (the organic thiophosphate formerly known as WR-2721) given to patients during myeloablative conditioning therapy for allogeneic bone marrow transplantation. Amifostine was given at a dose of 1000 mg/day of conditioning and was well tolerated if attention was given to serum calcium levels, blood pressure and antiemetics. Since August 1998, 60 patients (30 on each arm) have completed the study. There was no significant difference in the days to neutrophil or platelet engraftment in either arm of the study. Significantly, the duration of grade I-IV mucositis was decreased in the group that received amifostine (P=0.02). Also grade III or IV infections (P=0.008), duration of antibiotic therapy (P=0.03) and duration of fever (P=0.04) were significantly reduced with amifostine. However, there were no differences in the incidence of grade III or IV mucositis, liver toxicity or renal toxicity. There were also no differences in early mortality, relapse and long-term survival. We conclude that amifostine, while reducing the duration of mucositis and infections (possibly through some preservation of gut mucosal integrity), has a modest effect in allogeneic bone marrow transplants given the multiplicity of factors influencing organ toxicity and survival in this setting.

Variation in mortality and intraventricular haemorrhage in occupants of Pacific Rim nurseries

OBJECTIVE

A network of neonatal intensive care units in Pacific Rim countries was formed to compare infant risk factors, clinical practices, and outcomes for very low birthweight infants.

METHODOLOGY

A multicentre, prospective study compared outcomes for infants born smaller than 1501 g or at less than 31 weeks gestation.

RESULTS

Gestational age-specific survival and incidence of intracranial haemorrhage varied for infants born in these nurseries. We found differences in infant risk factors among the nurseries. There were also significant differences in the use of antenatal steroids, but similar rates for Caesarean section and surfactant treatment. The factor most predictive of neonatal death and severe intracranial abnormality was an elevated Clinical Risk Index for Babies (CRIB) score. Antenatal steroid treatment (>24 h prior to delivery) was associated with improved survival and decreased incidence of severe intracranial abnormalities. Antenatal steroid treatment for less than 24 h prior to delivery was not associated with improved survival. Caesarean delivery was associated with improved survival, but showed no benefit regarding the incidence of severe intracranial abnormality.

CONCLUSIONS

Our Pacific Rim nursery network found differences in neonatal outcomes that correlated best with measures of neonatal risk at birth, antenatal steroid treatment, and Caesarean delivery. These data emphasize the importance of obstetric care to improve postnatal outcomes in premature infants, and highlight the usefulness of CRIB scores in these patients.

Ureaplasma urealyticum and its association with chronic lung disease in Asian neonates

OBJECTIVE

The aim of the present prospective cohort study was to evaluate the relationship between lower respiratory tract colonization with Ureaplasma urealyticum and development of chronic lung disease (CLD) in a high-risk neonatal population.

METHODS

Prospective cohort study of preterm infants with a birthweight < 1,500 g needing mechanical ventilation within 24 h of birth in a tertiary care neonatal unit. Endotracheal aspirates from these infants were cultured within 24 h for U. urealyticum and the rate of colonization was determined. The primary outcome measure was the incidence of CLD at 28 days of life.

RESULTS

Of the 41 infants studied, 10 (24%) infants were colonized with U. urealyticum. The colonization rate was higher in babies < 1,000 g compared with babies weighing 1,000-1,500 g (P = 0.04). There was no significant difference between the colonized and non-colonized groups with regard to the antenatal use of steroids, maternal prolonged rupture of membranes, gestational age, birthweight, sex, respiratory distress syndrome, use of surfactant, patent ductus arteriosus and gastrooesophageal reflux. Of the 37 survivors, 20 (54%) developed CLD; eight infants (88.5%) in the colonized group developed CLD compared with 12 infants (42.8%) in the non-colonized group (P = 0.01).

CONCLUSIONS

Neonates colonized with U. urealyticum were twice as likely to have CLD than non-colonized babies (relative risk 2.01; 95% confidence interval 1.27-3.37). These data suggest a significant association between colonization with U. urealyticum and CLD in infants weighing < 1,500 g.

Perinatal drug abuse in KK Women's and Children's Hospital

No local figures are available in Singapore on the incidence of perinatal drug abuse and its effect on the foetus and the neonate. The objectives of this study were to determine the incidence of perinatal drug abuse and neonatal abstinence syndrome; to identify a maternal profile at high risk for substance abuse and to document the presenting features and treatment of infants with neonatal abstinence syndrome. Out of 14,690 births during the period January 1994 to December 1996, 38 (0.25%) had evidence of perinatal drug abuse. The study revealed that a high-risk maternal profile for drug abuse comprised of single mothers (52%); history of smoking (52%); no antenatal care (37%) and belonging to the Malay ethnic group (82%); and younger maternal age. Self-reporting was uncommon, occurring only in 8% and in 40% of cases, there was no known history of maternal drug addiction. The drug abused in all cases was heroin. Human immunodeficiency virus (HIV) screening was done only in a minority (21%) of the mothers and it was negative in all. Eighteen (47%) infants had evidence of neonatal abstinence syndrome with neurological manifestations being the commonest. Urine toxicology screening was positive in 26% of cases and had only 70% sensitivity and 41% positive predictive value. On follow up, default rate was high with 42% babies not attending follow up at the outpatient clinic. In conclusion, there is a need to maintain a high index of suspicion of substance abuse in those with high-risk maternal profile and their neonates should be closely watched for features of neonatal abstinence syndrome. Alternative methods of toxicology screening apart from urine need to be evaluated in order to improve the drug detection rate.

Blood pressure standards for very low birthweight infants during the first day of life

Blood pressures during the first day of life were measured prospectively in 61 very low birthweight infants using umbilical or peripheral arterial lines. Video recordings of real time waveforms were reviewed. Blood pressure correlated linearly with birthweight and gestation. Comparison with available standards showed that infants weighing under 800 g had lower acceptable mean arterial pressure (MAP). The lower limits of MAP for infants between 26 to 32 weeks of gestation were numerically similar to the gestational ages.

Persistence of anti-hypertensive effect after missed dose of perindopril

AIMS

To assess the persistence of the antihypertensive effect of the ACE-inhibitor perindopril after one missed dose.

METHODS

After a placebo run-in period, 10 hypertensive patients were started on perindopril 4 mg once daily in the morning, increased to 8 mg once daily after 4 weeks if office diastolic BP >85 mmHg. 24 h BP monitoring was performed at the end of the placebo run-in period and during active treatment in week 9 and 10 on either active treatment or a placebo-day using a double-blind, randomized, cross-over design.

RESULTS

Office BP decreased from 155+/-3/100+/-2 mmHg at the end of placebo to 139+/-3/89+/-2 mmHg (P<0.05 vs placebo) after 8 weeks of active treatment. After 2 months of active treatment, 24 h ABP showed significant decreases in day BP by -11+/-1/-7+/-1 mmHg and in night BP by -11+/-2/-7+/-1 mmHg while on active treatment. During the placebo-day, daytime BP showed decreases by -10+/-1/-5+/-1 and night BP by -8+/-2/-6+/-1 mmHg (NS vs active treatment day).

CONCLUSIONS

Perindopril 4-8 mg day-1 causes a persistent decrease in BP during the 24 h dosing interval, which is mostly maintained over the 24-48 h after dosing.

Parainfluenza type 3 viral outbreak in a neonatal nursery

An outbreak of parainfluenza virus type 3 infection that occurred in a special neonatal care unit is described. Birth weights of affected infants ranged from 1860 to 2080 g and gestational ages were between 28 and 32 weeks. Three infants presented with recurrent episodes of apnoea associated with oxygen desaturations on postnatal ages of 16 days, 26 days and 66 days respectively; upper respiratory tract infection symptoms such as coryza were absent in them. Two older infants who had oxygen dependent bronchopulmonary dysplasia presented with worsening of the respiratory status due to bronchiolitis at 5 and 6 months of age respectively. All infants required supplemental oxygen and assisted ventilatory support and there were no deaths. Parainfluenza virus type 3 was identified by direct antigen detection in 3 cases and was isolated in the other two. The outbreak was controlled by isolating the infected infants, use of gowns and strict hand washing. Nonporous surfaces contaminated with parainfluenza virus type 3 were cleansed with water and detergent. Viral respiratory infections should be considered in the differential diagnosis when growing premature infants present with recurrent apnoeic episodes and they may be severe enough to require assisted ventilatory support. The source of the outbreak was possibly a medical officer and a medical student who had an upper respiratory tract infection prior to the outbreak in the nursery. Medical and nursing staff with viral respiratory infections should avoid working in the nurseries until they are well.

Group B Streptococcal septicaemia/meningitis in neonates in a Singapore teaching hospital

Our aims were to establish the incidence and clinical characteristics of early and late onset Group B Streptococcal (GBS) septicaemia in neonates in our hospital over a period of 1 year. Routine screening for maternal GBS was not standard practice in the hospital. GBS was isolated from high vaginal swabs (HVS) obtained antenatally or postnatally for risk factors as determined by the obstetrician or neonatologist in charge. Data obtained were analyzed separately and these did not form part of the study. By a system of clinical case review and follow-up, mail, telephone and home visits, the outcome of all 15,062 livebirths in the hospital over a 1-year period were verified and reported. Our results show a low incidence of GBS infection in neonates in the hospital: early onset disease was 0.265 per 1,000 livebirths and late onset a quarter of that. The majority of our cases of early onset GBS disease were in premature infants. Because of our low incidence, prophylaxis schedules would have to ensure an acceptably smaller number of mothers exposed to antibiotics over and above the current level and the cooperation of our obstetricians. We have devised a schedule incorporating a current PROM (prelabour premature rupture of membranes) protocol which would result in only an additional 2.2% of mothers requiring prophylactic antibiotics.

Congenital candidiasis: varied presentations

Congenital candidiasis, especially the disseminated disease, is very uncommon but has been reported in very low birth weight infants. Five cases of congenital candidiasis, two with cutaneous type and three with systemic type, are described. All cases were symptomatic within the first 24 hours of life and none of them had significant risk factors such as the presence of foreign body in the maternal genital tract. Cutaneous candidiasis presented as extensive erythematous rash with infiltrative plaques in one and as bullous lesions in the other. Three infants who had disseminated candidiasis presented with extreme leukemoid reaction, severe hyperglycemia, and skin mottling with some patchy areas resembling first-degree burns, respectively. One infant had meningitis and the autopsy of another who died revealed several microabscesses containing Candida spores in the liver and lungs. The urine microscopy obtained by suprapubic bladder aspiration was found to be a good diagnostic marker of systemic invasion. The purpose of this report is to highlight the importance of recognizing candida as a possible pathogen in a critically ill neonate even though the clinical presentation may be nonspecific and varied. The presence of characteristic skin lesions of Candida species within 24 hours of life is an important clue to the possible diagnosis of congenital candidal infection. Even though very high mortality has been reported in congenital disseminated candidiasis, early recognition and treatment could give a favorable outcome.

Efficacy and tolerability of doxazosin versus enalapril in the treatment of patients with mild-to-moderate hypertension

The effects of 4 weeks of treatment with doxazosin or enalapril on diastolic blood pressure (DBP) and plasma lipid levels were studied in 160 patients 18 to 50 years old with mild-to-moderate hypertension. Comparing baseline measurements with measurements taken after 4 weeks, DBP was significantly reduced by 6.8 +/- 7.4 (mean +/- SD) mm Hg and 12.0 +/- 7.1 mm Hg in the doxazosin and enalapril groups, respectively. Systolic blood pressure was significantly decreased from baseline to end of treatment in both groups. There were no significant changes in heart rate from baseline to end of treatment in the doxazosin group, but there was a statistically significant decrease in heart rate in the enalapril group. High-density lipoprotein cholesterol increased statistically significantly in the doxazosin group but not in the enalapril group. A decrease in triglycerides was statistically significant with respect to the doxazosin group and was close to significance for the enalapril group. Forty-nine (62%) patients in the doxazosin group and 43 (54%) patients in the enalapril group reported at least one adverse event. Significant reductions in DBP after 4 weeks of treatment were achieved by both drugs, each taken once daily. This reduction was more pronounced in the enalapril group 24 hours postdose, with a mean final daily dose of 2.8 mg of doxazosin and 12.6 mg of enalapril. However, even relatively short-term treatment with low-dose doxazosin showed a more favorable effect on lipids than did enalapril.

Is 'herbal health tonic' safe in pregnancy; fetal alcohol syndrome revisited

So called 'Herbal Health Tonics' are freely available in the market. This has been promoted by the manufacturers for the following symptoms: poor appetite, gastroenteric weakness, poor blood circulation, chills, fatigue, weak constitution and weakness after disease. We report a case of suspected fetal alcohol syndrome (FAS). A baby boy of 3,700 g born to a 29-year-old Chinese mother at 41 weeks' gestation was found to have features consistent with FAS. On follow up at 3 years of age, both motor and mental milestones as well as speech and language were delayed suggesting the possibility of FAS. There was a history of maternal ingestion of 'Herbal Health Tonic' (which contained 14% alcohol) daily for the first 2 months of the antenatal period. She denied exposure to alcohol or any other drugs. The authors would like to highlight the risk of such 'Herbal Health Tonics' in pregnancy and their probable deleterious effects on the growing fetus. We feel that it is extremely important to look into the traditional practices among pregnant women in Singapore and in other parts of the world where there are similar practices, otherwise more cases like these could occur in future.

The 'TRAP' sequence--life threatening consequences to the pump twin

The acardius foetal malformation is a rare abnormality occurring in monozygotic multiple pregnancies. This is a case report of a pair of twins with the "twin reversed arterial perfusion (TRAP)" sequence and its complications. The recipient twin was born acardius acephalus. The pump twin had problems of prematurity, disseminated intravascular coagulation, sclerema and right ventricular hypertrophy. On follow-up at seven months he has failure to thrive, spastic quadriplegia and developmental delay. An awareness of the TRAP sequence may lead to better antenatal diagnosis and optimal management of the twin pregnancy.

An outbreak of methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit in Singapore: a 20-month study of clinical characteristics and control

Methicillin resistant Staphylococcus aureus (MRSA) is a major infection control problem in many countries. There have been many reports of outbreaks in neonatal nurseries including, in our part of the world, Australia, Hong Kong and Malaysia. A recent outbreak of MRSA in the neonatal intensive care unit in the Kandang Kerbau Hospital, Singapore, presented us with the opportunity to study the clinical characteristics of the outbreak and the effects of infection control measures. Neonates admitted to the neonatal intensive care unit were studied over a 20-month period. They were all screened for nasal colonisation on admission and weekly thereafter. Infections were documented. Over this period there were altogether 2,576 admissions of which 85 infants had nasal colonisation with MRSA (3.3%) and 28 developed infections (1%). Although the majority of infants colonised by MRSA suffered no ill effects, 3 had septicaemia and 2 had septicaemia with osteomyelitis. There were no deaths. Standard infection control measures with barrier nursing and the use of mupirocin nasal ointment were ineffective, and control was achieved only after strict cohorting together with the use of mupirocin was instituted. This was done without additional costs to the department and without additional nurses or doctors.

A survey of postoperative wound infections in obstetrics and gynaecology--the Kandang Kerbau Hospital experience

Postoperative wound infection is of great importance to both the surgeon and patient. This study covers 6,639 major operations in Kandang Kerbau Hospital, Singapore over a 12-month period. The overall wound infection rate was 2.26%. The highest wound infection rate occurred in hysterectomies and the lowest in laparoscopies. There was a good correlation between monthly caesarean wound infection rate and number of caesarean sections. Staphylococcus aureus was the most common organism isolated. The wound infection rate was also higher in crowded wards and among some surgeons. After distribution of the survey results, we noted a decrease in wound infection rate for some surgeons and a changing pattern in the use of antibiotics. A further study of other risk factors was encouraged.

Acute glomerulonephritis--changing patterns in Singapore children

This study compared the pattern of acute glomerulonephritis (AGN), a disease known to be influenced by socioeconomic and environmental factors, in children 12 years and under, for the years 1971 and 1985. All children admitted to the four major paediatric departments with haematuria and at least two of the following (oedema, hypertension or oliguria) had an initial diagnosis of AGN. A sample population from one unit from 1980 to 1984 showed that over 70% of these children had evidence of a post-streptococcal aetiology. In 1971, 411 children were admitted with AGN, as compared with only 58 in 1985. The age-sex-race standardized rates for 1971 and 1985 were 0.632 and 0.023/1,000 children 12 years and under, respectively (P less than 0.001). The mean age of presentation was lower in 1971. Over this period, Singapore saw a threefold rise in the gross national product, accompanied by rapid urbanization. On analysis of the housing pattern, only 31% of the children lived in high-rise apartments in 1971, in contrast with 86% in 1985 (P less than 0.001). The majority of non-apartment dwellers had homes in rural districts. From an epidemiological perspective, factors which could have led to the highly significant decline in prevalence of AGN in Singapore children included improvement in the socioeconomic status and health care system, and urbanization of the country.

Reliability of the Dinamap non-invasive monitor in the measurement of blood pressure of ill Asian newborns

Four hundred thirty-one paired sets of readings of systolic and diastolic blood pressure and 438 paired sets of readings of mean arterial BP from 49 ill newborns, including 21 very low birth weight infants, were analyzed for the extent and pattern of agreement and the linear relationship between the Dinamap oscillometric monitor and the direct intraarterial blood pressure readings. Agreement between the two methods was measured by the intraclass correlation, whereas the linear relationship was assessed by the product-moment correlation. The intraclass correlations for systolic, diastolic and mean blood pressures were 0.696, 0.766, and 0.781, respectively. The product-moment correlations for systolic, diastolic and mean blood pressures were 0.706, 0.768, and 0.786, respectively. BP measurements by the Dinamap monitor showed reasonably close agreement to those obtained by the intraarterial mean arterial pressure ranges above 40 mmHg. For mean arterial pressure of 40 mmHg and lower, BP readings by the Dinamap monitor tended to be higher than those obtained by the intraarterial method. These findings appeared to be consistent regardless of the birth weight of the newborn.

Neonatology in Singapore

A short account of the history of Neonatology in Singapore is given. Current practice and results of management of neonates are highlighted and future directions for neonatology in Singapore outlined. Brief mention is made of 2 common controversies in neonatal practice.

Kawasaki disease--the Singapore experience

50 children with Kawasaki disease were seen between September 1983 to March 1988. Their ages ranged from 3 months to 10 years with a mean age of 25 months. Male to Female ratio was 2.3 to 1. The diagnosis of Kawasaki disease was made between the fourth to fifteenth day of illness. Marked thrombocytosis, raised erythrocyte sedimentation rate, leucocytosis, mild anemia and sterile pyuria were common features. All patients had a normal ECG and chest X-ray. 2D echocardiogram was done in the sub-acute phase of the illness in every patient. Sixteen patients (32%) had coronary artery dilatation. Thirteen of these had serial 2D echocardiograms done over a period of more than one year. Twelve had echocardiographic resolution of the coronary lesion within 18 months of follow up. Patients with coronary artery dilatation were significantly younger. All had full clinical recovery with aspirin therapy. Kawasaki disease afflicts mostly young children and can present as a diagnostic problem. Coronary artery involvement is common, and except for age, it is not predictable by any clinical or laboratory parameter. Serial echocardiographic examinations are necessary in the management of these patients.

HLA-DR antigens in Chinese children with insulin-dependent diabetes mellitus

We studied the distribution of HLA-DR and MT1, MT2, MT3 genotypes in 23 Chinese children with insulin-dependent diabetes mellitus (IDDM). The frequency of DR3 was 48% in IDDM children compared to 14% of normal controls (corrected p = 0.0098, RR = 5.70). The frequency of DR4 was not increased. These differences when compared with the results of Western populations may contribute to the relative rarity of IDDM among Chinese children.

HLA-system in Chinese children with insulin-dependent diabetes mellitus: a strong association with DR3

We studied the distribution of HLA-A, B, and DR and MT1, MT2, MT3 genotypes in all 20 Chinese children with insulin-dependent diabetes mellitus (IDDM) attending the four government pediatric units in Singapore. We found an increase in HLA BW22 but the corrected probability value was not statistically significant. AW33 and B17 were observed in 50% and 55% of IDDM children, respectively, compared with 11% and 13% of normal controls, respectively. The values for AW33 were as follows: corrected P = 0.00094 and relative risk (RR) = 8.17; for B17 they were corrected P = 0.001 and RR = 7.55. In addition, the frequency of DR3 was 50% in IDDM children compared with 14% of normal controls (corrected P = 0.0019, RR = 6.20). AW33, B17, and DR3 are in linkage disequilibrium in our normal Chinese population. All ten patients who were positive for DR3 also had B17. The frequency of DR4 was not increased, and there were no protection IDDM related antigens found. These differences compared with the results in Western populations may contribute to the relative rarity of IDDM among Chinese children.

Five years' experience with aortocoronary bypass grafting

During a 5-year period (Apr. 14, 1970 to Apr. 14, 1975) 930 patients underwent aortocoronary bypass grafting; the procedure was done as an emergency in 141. Of the entire group 3.3% died at operation, 1.6% died in hospital and 5.8% died later; of the patients undergoing emergency grafting 12.1% died at operation and 5.7% died later. From a detailed analysis of the first 600 patients it was found that both operative and late mortality were clearly related to two factors: severe left ventricular dysfunction at the time of operation and inadequate surgical treatment because of insertion of insufficient numbers of grafts or because of poor blood flow through the grafts.

The synthesis of Benzo[4,5]cyclohepta[1,2,3-de]naphthalene

Muller et al have recently reported a synthesis of benzo[4,5] cyclohepta[1,2,3-de]naphthalene by a dehydrogenation reaction. Some investigations into alternative routes to this compound are now reported. One of these succeeded in giving a compound identical with that described by the previous workers.