Joint spatial modelling of disease risk using multiple sources: an application on HIV prevalence from antenatal sentinel and demographic and health surveys in Namibia.

BACKGROUND: In disease mapping field, researchers often encounter data from multiple sources. Such data are fraught with challenges such as lack of a representative sample, often incomplete and most of which may have measurement errors, and may be spatially and temporally misaligned. This paper presents a joint model in the effort to deal with the sampling bias and misalignment. METHODS: A joint (bivariate) spatial model was applied to estimate HIV prevalence using two sources: 2014 National HIV Sentinel survey (NHSS) among pregnant women aged 15-49 years attending antenatal care (ANC) and the 2013 Namibia Demographic and Health Surveys (NDHS). RESULTS: Findings revealed that health districts and constituencies in the northern part of Namibia were found to be highly associated with HIV infection. Also, the study showed that place of residence, gender, gravida, marital status, number of kids dead, wealth index, education, and condom use were significantly associated with HIV infection in Namibia. CONCLUSION: This study had shown determinants of HIV infection in Namibia and had revealed areas at high risk through HIV prevalence mapping. Moreover, a joint modelling approach was used in order to deal with spatially misaligned data. Finally, it was shown that prediction of HIV prevalence using the NDHS data source can be enhanced by jointly modelling other HIV data such as NHSS data. These findings would help Namibia to tailor national intervention strategies for specific regions and groups of population.

Household and community variations and nested risk factors for diarrhoea prevalence in southern Malawi: a binary logistic multi-level analysis.

This paper examines household and community-level influences on diarrhoeal prevalence in southern Malawi. A Bayesian multi-level modelling technique is used in the estimation of hierarchically built data from a survey of individuals nested within households nested within communities. Households have strong unobserved influence on diarrhoeal illness (sigma(2)(u) = 4.476; 95% CI: 2.081, 6.871). A joint Wald test of significance shows that an individual's age [chi(2)(4) = 55.921, p = 0.000] and school [chi(2)(2) = 18.203, p = 0.000] have strong influence on an individual's diarrhoeal prevalence. An individual's history of malarial-like illness also has a strong positive relationship with diarrhoeal prevalence [beta = 0.606, p = 0.000]. Household factors that influence diarrhoea include employment status of head of household [beta = -0.619, p < 0.021], maternal age [beta = -0.013, p < 0.003], and size of household [beta = -0.669, p = 0.000]. The positive relationship between diarrhoea and malaria-like episodes highlights common risk factors hence the need for common approaches to combat the diseases. Significant household effects underline the importance of household considerations in policy issues.

Care-Seeking Behaviour and Implications for Malaria Control in Southern Malawi

Although malaria is a controllable and preventable disease; it remains among the leading causes of mortality and morbidity in southern Malawi. The importance of early diagnosis and prompt treatment with hospital prescribed drugs and effective home management to control malaria is well established; however; these in part depend on how households make their decisions when family members have suffered from malaria. This study examines the behaviour of households with regard to decisions they make in managing malaria illness. Using hierarchically built data from a survey of 1;400 mothers nested within 33 communities; a series of two-level logistic regression models with Bayesian estimation was used to determine predictors of care-seeking behaviour towards malaria when a family member or a child was perceived to have malaria. The results show that most families normally visit or use medication prescribed at health facilities for both adult (80) and child (86) members when they are perceived to have malaria. The main obstacle to accessing the nearest health facility was distance and transport costs (73) and the main problems encountered at health facilities were long waiting time or absence of health workers (73) and shortage of drugs (35). Among the main predictor variables for choices of treatment for childhood malaria was the absence of a health surveillance assistant for those that visited hospitals [Beta=0.56; 95CI:-0.86;-0.26]; bought medication from open markets [Beta=0.51; 95CI:0.20;0.82]; and those that used other traditional methods or did nothing [Beta=0.70; 95CI:-0.04;1.44; p=0.06].. The results have an important role to play in the control and prevention of malaria in Malawi. The results reveal the need for increased awareness about the dangers of purchasing drugs from non-medical and/or uncertified private institutions and sources such as those found in open markets. They also show the important role of community health workers in the delivery of health systems. The study recommends empowerment of community health workers through rigorous and relevant health promotion programmes to update both their knowledge and their skills in communication and counselling

Care-Seeking Behaviour and Implications for Malaria Control in Southern Malawi

Abstract:Although malaria is a controllable and preventable disease; it remains among the leading causes of mortality and morbidity in southern Malawi. The importance of early diagnosis and prompt treatment with hospital prescribed drugs and effective home management to control malaria is well established; however; these in part depend on how households make their decisions when family members have suffered from malaria. This study examines the behaviour of households with regard to decisions they make in managing malaria illness. Using hierarchically built data from a survey of 1;400 mothers nested within 33 communities; a series of two-level logistic regression models with Bayesian estimation was used to determine predictors of care-seeking behaviour towards malaria when a family member or a child was perceived to have malaria. The results show that most families normally visit or use medication prescribed at health facilities for both adult (80) and child (86) members when they are perceived to have malaria. The main obstacle to accessing the nearest health facility was distance and transport costs (73) and the main problems encountered at health facilities were long waiting time or absence of health workers (73) and shortage of drugs (35). Among the main predictor variables for choices of treatment for childhood malaria was the absence of a health surveillance assistant for those that visited hospitals [?=0.56; 95 CI:-0.86;-0.26]; bought medication from open markets [?=0.51; 95 CI:0.20;0.82]; and those that used other traditional methods or did nothing [?=0.70; 95

Performance of selected nonparametric tests for discrete longitudinal data under different patterns of missing data.

Comparison of changes over time of a continuous response variable between treatment groups is often of main interest in clinical trials. When the distributional properties of the continuous response variable are not regular enough, or when the response is discrete, nonparametric techniques have been used. The relative performances of selected repeated measures nonparametric two-sample tests proposed by Wei and Lachin, Koziol, Wei and Johnson, and the adapted Wilcoxon Rank-Sum test are compared through simulations based on quality of life data. The Wilcoxon Rank-Sum test is the most powerful and is not significantly affected by the different patterns of missing data.

Suicidal ideation and associated factors among in-school adolescents in Zambia.

A cross sectional study was conducted to estimate the prevalence and correlates of suicidal ideation among in-school adolescents in Zambia. Backward logistic regression analysis was conducted to assess the association between relevant predictor variables and suicidal ideation within the last 12 months. A total of 1970 in-school adolescents who participated in the Zambia Global School-Based Health Survey in 2004 responded to the question on suicidal ideation. Overall, 54.0% were males, 40.8% were current drinkers, and 35.9% ever smoked marijuana (cannabis). Altogether 31.3% reported suicidal ideation in the past 12 months (males = 31.1%; females = 31.4%). Being male (OR = 1.05; 95%CI 1.03, 1.05): being <14 years old (OR = 1.21; 95%CI 1.19, 1.23), having been drunk (OR = 1.28; 95%CI 1.27, 1.29). worried (OR= 1.05; 95%CI 1.04, 1.06), sad or hopeless in the past 12 months (OR = 1.02; 95%CI 1.01, 1.03) and ever used marijuana (OR = 1.18; 95%CI 1.17, 1.19) were positively associated with suicidal ideation. Loneliness appeared to be protective (OR = 0.92; 95%CI 0.91, 0.92). All the results, except for ever smoked marijuana and ever been drunk, may have been biased due to non-response to the question on suicidal ideation. A series of cross sectional studies should be conducted to monitor changes in behavioural factors among others ever smoked marijuana and ever been drunk in order to broaden our understanding of factors that may be causing adolescents to seriously consider committing suicide.