Model-based inference for small area estimation with sampling weights

Obtaining reliable estimates about health outcomes for areas or domains where only few to no samples are available is the goal of small area estimation (SAE). Often, we rely on health surveys to obtain information about health outcomes. Such surveys are often characterised by a complex design, stratification, and unequal sampling weights as common features. Hierarchical Bayesian models are well recognised in SAE as a spatial smoothing method, but often ignore the sampling weights that reflect the complex sampling design. In this paper, we focus on data obtained from a health survey where the sampling weights of the sampled individuals are the only information available about the design. We develop a predictive model-based approach to estimate the prevalence of a binary outcome for both the sampled and non-sampled individuals, using hierarchical Bayesian models that take into account the sampling weights. A simulation study is carried out to compare the performance of our proposed method with other established methods. The results indicate that our proposed method achieves great reductions in mean squared error when compared with standard approaches. It performs equally well or better when compared with more elaborate methods when there is a relationship between the responses and the sampling weights. The proposed method is applied to estimate asthma prevalence across districts.

Foodborne Illness Among School Children in Ga East, Accra

BACKGROUND

A food borne illness was reported in Ga-East district of Greater Accra Region among school children in May, 2007 after eating food provided at school. The objective of the investigation was to determine the source, mode of contamination and the causative agent.

METHODS

A case-control study was conducted, cases were schoolchildren with abdominal symptoms and controls were children of the same sex and class without any symptom during the same period. The school children were selected by systematic sampling. Food handlers and the children were interviewed by a structured questionnaire. Food handlers were physically examined and their stools and blood examined. The kitchen for food preparation was inspected. Risks of food borne infection from the foods eaten were determined using attack rates.

RESULTS

The minimum, peak and maximum incubation periods were 2, 11 and 61 hours respectively. The source was rice and groundnut soup (with the highest attack rate difference). Stool and blood samples of food handlers were not infective. Storage facility for food items was poor. No food samples were available for organism isolation. A protocol to prevent such outbreaks was nonexistent.

CONCLUSION

The short incubation period and symptoms presented suggest an infective origin. The storage of the meat may potentially have been the point of contamination. The study showed that the schoolchildren ate contaminated food although the investigation could not determine the causative agent. Protocols to prevent such outbreaks need to be developed for the schools.

Filtration to reduce paediatric dose for a linear slot-scanning digital X-ray machine

This paper describes modelling, application and validation of a filtration technique for a linear slot-scanning digital X-ray system to reduce radiation dose to paediatric patients while preserving diagnostic image quality. A dose prediction model was implemented, which calculates patient entrance doses using variable input parameters. Effective dose is calculated using a Monte Carlo simulation. An added filter of 1.8-mm aluminium was predicted to lower the radiation dose significantly. An objective image quality study was conducted using detective quantum efficiency (DQE). The PTW Normi 4FLU test phantom was used for quantitative assessment, showing that image contrast and spatial resolution were maintained with the proposed filter. A paediatric cadaver full-body imaging trial assessed the diagnostic quality of the images and measured the dose reduction using a 1.8-mm aluminium filter. Assessment by radiologists indicated that diagnostic quality was maintained with the added filtration, despite a reduction in DQE. A new filtration technique for full-body paediatric scanning on the Lodox Statscan has been validated, reducing entrance dose for paediatric patients by 36 % on average and effective dose by 27 % on average, while maintaining image quality.

The cost of treatment failure: resource use and costs incurred by hepatitis C virus genotype 1-infected patients who do or do not achieve sustained virological response to therapy

Chronic hepatitis C virus (HCV) infection places a considerable economic burden on health services. Cost-effectiveness analyses of antiviral treatment for patients with chronic HCV infection are dependent on assumptions about cost reductions following sustained virological response (SVR) to therapy. This study quantified the medium-term difference in health resource usage and costs depending on treatment outcome. Retrospective chart review of patients with HCV genotype 1 infection who had received at least 2 months pegylated interferon and ribavirin therapy, with known treatment outcome was conducted. Disease status was categorized as chronic hepatitis, cirrhosis or decompensated liver disease. Health resource use was documented for each patient in each disease state. Unit costs were from the NHS 'Payment by Results' database and the British National Formulary. One hundred and ninety three patients (108 SVR, 85 non-SVR) with mean follow-up of 3.5 (SVR) and 4.9 (non-SVR) years were enrolled. No SVR patient progressed to a more severe liver disease state. Annual transition rates for non-SVR patients were 7.4% (chronic hepatitis to cirrhosis) and 4.9% (cirrhosis to decompensated liver disease). By extrapolation of modelled data over a 5-year post-treatment period, failure of patients with chronic hepatitis to achieve SVR was associated with a 13-fold increase (roughly £2300) in costs, whilst for patients who were retreated, the increase was 56-fold, equating to more than £10 000. Achievement of an SVR has significant effects on health service usage and costs. This work provides real-life data for future cost-effectiveness analyses related to the treatment for chronic HCV infection.

Effect of aluminium filtration on dose and image quality in paediatric slot-scanning radiography

This paper examines the effect that a 1.8 mm aluminium filter has on paediatric patient dose and image quality for linear slot scanning radiography (LSSR). A dynamic dose prediction model for LSSR accurately predicted the dose reduction effects of added aluminium filtration. A cadaver imaging study was carried out to assess the effects of filtration on image quality. With 1.8 mm added aluminium filtration, no visible degradation to image contrast or clarity was found, and in some cases the aluminium filtration improved the image quality as judged by radiologists.

Service provision for liver disease in the UK: a national questionnaire-based survey

The National Plan for Liver Services in 2009 called for a review of current liver services across the UK to identify areas of good and poor provision. We present the results of a national questionnaire survey of liver services, which focussed on staffing and training, access to key facilities and clinical management of liver disease. Areas of good practice include the increased proportion of consultants who trained at a liver centre, the introduction of specific liver clinics and the widespread use of terlipressin and antibiotics for variceal bleeding. Areas of poor practice include limited access to alcohol psychiatry services and transjugular intrahepatic portosystemic shunts (TIPS) and limited recording of outcome measures or patient databases. Wide variation in the clinical management of serious liver diseases supports the need for managed clinical networks. These results will help to guide the development of standards of care for liver services across the UK.

Approximate Bayesian computation reveals the factors that influence genetic diversity and population structure of foxsnakes

Contemporary geographical range and patterns of genetic diversity within species reflect complex interactions between multiple factors acting across spatial and temporal scales, and it is notoriously difficult to disentangle causation. Here, we quantify patterns of genetic diversity and genetic population structure using mitochondrial DNA sequences (101 individuals, cytochrome b) and microsatellites (816 individuals, 12 loci) and use Approximate Bayesian computation methods to test competing models of the demographic history of eastern and western foxsnakes. Our analyses indicate that post-glacial colonization and past population declines, probably caused by the infilling of deciduous forest and cooler temperatures since the mid-Holocene, largely underpin large-scale genetic patterns for foxsnakes. At finer geographical scales, our results point to more recent anthropogenic habitat loss as having accentuated genetic population structure by causing further declines and fragmentation.

Electronic learning and open educational resources in the health sciences in ghana

OBJECTIVES

To determine whether a group of Ghanaian students are able to easily use electronic learning material and whether they perceive this method of learning as acceptable.

SETTING

The University of Ghana Medical School (UGMS) and the School of Medical Sciences (SMS), Kwame Nkrumah University of Science and Technology (KNUST) PARTICIPANTS: One hundred and fifty third year medical students at SMS and nineteen fifth year medical students at UGMS METHODS: Two e-learning materials were developed, one on the polymerase chain reaction and the other on total abdominal hysterectomy and these were distributed to selected medical students. Two weeks after the distribution of the programmes, a one-page, self-administered questionnaire was distributed to the target groups of students at the two institutions.

RESULTS

Ninety three percent (139) of respondents at KNUST and 95% (18) at UG report having access to a computer for learning purposes. All of the UG students viewed the TAH programme; 82% (130) of the KNUST students viewed the PCR animations. All students who viewed the programmes at both institutions indicated that the e-learning pro-grammes were "more effective" in comparison to other methods of learning.

CONCLUSION

Computer ownership or availability at both medical schools is sufficient to permit the distribution and viewing of e-learning materials by students and the medical students considered both programmes to be very helpful.

A comparison of the natural history and outcome of treatment for Asian and non-Asian hepatitis C-infected patients

Ethnicity is an important host variable, but its impact on disease progression and response to therapy in Hepatitis C infection is unclear. Here we compare the natural history and outcome of therapy in white and Asian (Indian subcontinent) Hepatitis C infected patients. A total of 2123 White and 120 Asian HCV infected patients were identified within the Trent HCV study. Response to therapy was assessed in 224 white and 46 Asian patients with genotype 3 infection who received pegylated interferon and ribavirin. Asian patients were more likely to be older, female, infected with genotype 3 and to consume no alcohol. At time of first biopsy, fibrosis stage was significantly higher in Asian patients than in Whites (3.0 ± 2.3 vs 1.8 ± 2.0, P < 0.001), as were necro-inflammation and steatosis scores. However, in those patients where duration of infection could be estimated, fibrosis progression was similar for both groups (0.25 ± 0.31 vs. 0.16 ± 0.54 Ishak points/year, P = 0.068). 78.3% of Asian and 67.9% of White genotype 3 patients had a sustained virological response following Pegylated Interferon and Ribavirin. Cirrhosis and increased levels of GGT, but not ethnicity were associated with a reduction in the likelihood of a sustained virological response on multivariate analysis. Asian patients with Hepatitis C are more likely to be female, less likely to give a history of risk factors, present to medical services at an older age, and have more severe liver disease at diagnosis, but disease progression and response to treatment are similar to white patients.

Antibody fragments as tools in crystallography

While antibody-based therapeutics have become firmly established as front-line drugs, the use of antibodies as research tools in small molecule drug discovery is still in its infancy. In this review we focus on the use of antibody fragments as crystallization chaperones to aid the structural determination of otherwise 'uncrystallizable' or 'undruggable' target proteins. We also highlight a potential application for this technology, in which antibody-mediated structures may be used to inform the design of new chemical entities.

Staffs' knowledge and perceptions of working with women with intellectual disabilities and mental health problems

AIM

There is a growing evidence of the physical and mental health inequalities in people with intellectual disability (ID) although less has been written concerning the mental health of women with ID (International Association for the Scientific Study of Intellectual Disabilities). This is compared with the substantive literature published within mainstream psychiatry on gender. The aim of this study was to explore a range of health and social care staffs' knowledge and perceptions of caring for women with ID who have mental health problems focusing upon risk and resilient/protective factors.

METHOD

A qualitative methodology was used. Eight focus groups were conducted with hospital, community and residential staff across one region of the UK. The focus groups were audiotaped and the transcriptions were subjected to a thematic content analysis using Newell & Burnard's framework.

FINDINGS

Six inter-related risk factors were identified by the participants as potential causes for the women with ID to develop a mental illness and these were: having an ID and being female, unmet expectations, dysfunctional family upbringing, unstable relationships/loss of children, domestic violence and negative life experiences. Few of the participants acknowledged hormonal issues as a risk factor. Resilient/protective factors included being proactive, greater community participation, early recognition and mental health maintenance.

CONCLUSION

These results are discussed in light of current developments and policy within mainstream psychiatric gender approaches. Greater recognition of a proactive health approach for both staff and women with an ID is recommended.

Hepatitis C virus-infected patients with a persistently normal alanine aminotransferase: do they exist and is this really a group with mild disease?

Opinion varies on whether or not hepatitis C virus (HCV) infected patients with persistently normal aminotransferase (PNALT) levels represent a group with mild disease. To evaluate the risk of ALT flare and fibrosis progression in patients with PNALT followed up as part of the Trent HCV cohort. Treatment-naïve patients with an elevated ALT (n = 1140) or PNALT, the latter defined as either an ALT < or = 30 IU/L (n = 43) or an ALT < or = 40 IU/L (n = 87) on > or =2 occasions in the 6 months following diagnosis, and no ALT > 40 U/L were included. The likelihood of maintaining a PNALT < or = 30 IU/L was 42.2% and PNALT < or = 40 IU/L 41.7% at 3 years. The Ishak fibrosis score was > or =3 in 3.7%, 8.3% and 29.6% of patients with PNALT < or = 30 IU/L, PNALT < or = 40 IU/L and elevated ALT, respectively. Fibrosis progression between paired biopsies was similar for patients with PNALT < or = 30 IU/L (0.33 +/- 0.94 Ishak fibrosis points/year), PNALT < or = 40 IU/L (0.35 +/- 0.82) and elevated ALT (0.19 +/- 0.48). The majority of those defined as PNALT subsequently have an abnormal ALT. They have a similar risk of disease progression to other HCV infected patients and, therefore, warrant the same consideration with regard to treatment.

Listening to women with intellectual disabilities and mental health problems: a focus on risk and resilient factors

Women without intellectual disabilities are more likely to develop mental health problems as a result of physiological functioning and psychosocial risk factors. However, little is known about the mental health of women with intellectual disabilities. The aim of this study was to explore a small group of women's perceptions of the risk and protective factors pertaining to their mental health conditions. Twelve semi-structured interviews were conducted in 2007 in Northern Ireland. Thematic content analysis identified three risk factors and four protective/resilient factors. None of the women identified physiological functioning as a risk factor. Results suggest that women with intellectual disabilities experience psychosocial risk factors similar to those reported by women without intellectual disability. Additional risk factors place them at higher risk of developing mental health problems. However, more research is required.

Listening to women with intellectual disabilities and mental health problems: a focus on risk and resilient factors

Women without intellectual disabilities are more likely to develop mental health problems as a result of physiological functioning and psychosocial risk factors. However, little is known about the mental health of women with intellectual disabilities. The aim of this study was to explore a small group of women's perceptions of the risk and protective factors pertaining to their mental health conditions. Twelve semi-structured interviews were conducted in 2007 in Northern Ireland. Thematic content analysis identified three risk factors and four protective/resilient factors. None of the women identified physiological functioning as a risk factor. Results suggest that women with intellectual disabilities experience psychosocial risk factors similar to those reported by women without intellectual disability. Additional risk factors place them at higher risk of developing mental health problems. However, more research is required.

Effect of improved home ventilation on asthma control and house dust mite allergen levels

BACKGROUND

The warm, humid environment in modern homes favours the dust mite population, but the effect of improved home ventilation on asthma control has not been established. We tested the hypothesis that a domestic mechanical heat recovery ventilation system (MHRV), in addition to allergen avoidance measures, can improve asthma control by attenuating re-colonization rates.

METHODS

We conducted a randomized double-blind placebo-controlled parallel group trial of the installation of MHRV activated in half the homes of 120 adults with asthma, allergic to Dermatophagoides pteronyssinus. All homes had carpets steam cleaned and new bedding and mattress covers at baseline. The primary outcome was morning peak expiratory flow (PEF) at 12 months.

RESULTS

At 12 months, the primary end-point; change in mean morning PEF as compared with baseline, did not differ between the MHRV group and the control group (mean difference 13.5 l/min, 95% CI: -2.6 to 29.8, P = 0.10). However, a secondary end-point; evening mean PEF, was significantly improved in the MHRV group (mean difference 24.5 l/min, 95% CI: 8.9-40.1, P = 0.002). Indoor relative humidity was reduced in MHRV homes, but there was no difference between the groups in Der p 1 levels, compared with baseline.

CONCLUSIONS

The addition of MHRV to house dust mite eradication strategies did not achieve a reduction in mite allergen levels, but did improve evening PEF.

Autoantibodies in chronic hepatitis C virus infection and their association with disease profile

Autoantibodies are commonly detected in chronic hepatitis C (HCV) but their significance remains uncertain. We assessed the prevalence of anti-nuclear (ANA) and anti-smooth muscle (ASM) antibodies within a cohort of 963 treatment-naïve HCV patients. We also assessed for differences between autoantibody-positive and autoantibody-negative patients in demographics, markers of disease activity and response to anti-viral treatment. One hundred and seventy-two patients (17.9%) had at least one autoantibody, of which were 104 (10.8%) ASM, 54 (5.6%) ANA and 14 (1.5%) positive for both. Autoantibody-positive patients were older (43 vs 39 years, P = 0.001) caused by an age-related increase in ANA (but not ASM). There were no differences in gender, alcohol intake, ethnicity or viral genotype. The presence of autoantibodies, and specifically ASM, was associated with an increase in interface hepatitis score amongst men (1.1 vs 0.8, P = 0.005) but no difference in other necroinflammatory measures, liver function tests or immunoglobulins (Ig). There was no difference in initial fibrosis stage or rate of fibrosis progression. Autoantibodies did not affect response to anti-viral treatment. We conclude that autoantibodies are frequent in HCV infection. Anti-nuclear antibodies increase with age, whereas ASM antibodies are associated with interface hepatitis in men. Neither autoantibody carries increased risk of fibrosis progression or failure of therapy.

The many faces of hydatid disease

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