Doctoral Degrees (Epidemiology and Biostatistics)

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Browsing Doctoral Degrees (Epidemiology and Biostatistics) by Subject "HIV (Viruses) -- Epidemiology -- South Africa"

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    An evaluation of the effectiveness of task-shifting health systems approaches, including community-based and pharmaceutical care models, for HIV treatment and prevention programs in South Africa
    (Stellenbosch : Stellenbosch University, 2020-12) Fatti, Geoffrey; Chikte, Usuf M. E.; Nachega, Jean; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Global Health. Epidemiology and Biostatistics.
    ENGLISH SUMMARY : Southern Africa is the epicenter of the human immunodeficiency virus (HIV) pandemic having the highest burden of HIV globally. Although South Africa has made great strides with the roll-out of its antiretroviral treatment (ART) program, ongoing challenges include high attrition of patients from ART care and ongoing elevated HIV incidence. There is also a severe shortage of professional health workers in the region, which impacts HIV program delivery. Task-shifting health systems approaches have been developed in order for the health system to provide large-scale HIV program delivery with limited numbers of professional health workers. This thesis evaluates the effectiveness of task-shifting health systems interventions in HIV prevention and treatment programs in South Africa, including community-based programs utilizing community healthcare workers (CHWs), and pharmaceutical care models. Data were collected in cohort studies conducted between 2004 and 2015/2016 in four provinces of South Africa. The results chapters of the thesis are presented in the form of published papers. The first paper evaluates the effectiveness of a community-based support (CBS) program amongst a large cohort of adults living with HIV receiving ART up to five years after ART initiation. Adults who received CBS had improved ART outcomes, including improved patient retention with lower loss to follow-up and lower mortality, both of which were reduced by one third. The second paper evaluates the effectiveness of a community-based combination HIV prevention intervention delivered by CHWs for pregnant and postpartum women in a high HIV incidence district in KwaZulu-Natal. Maternal HIV incidence amongst participants who received the intervention was considerably lower compared to other studies from the region. The paper further recommends expanded roll-out of home-based couples HIV counselling and testing, and initiating oral pre-exposure prophylaxis for HIV particularly for pregnant women within serodiscordant couples, in order to reduce maternal HIV incidence. The third paper compares the effectiveness and cost of two task-shifting pharmaceutical care models for ART delivery in South Africa, namely the indirectly supervised pharmacist assistant (ISPA) model and the nurse-managed model. The ISPA model was found to have a higher quality of pharmaceutical care, was less costly to implement and was possibly associated with improved patient clinical outcomes. The fourth paper evaluates the effectiveness and cost-effectiveness of CBS for adolescents and youth receiving ART at 47 health facilities in South Africa. CBS was found to substantially reduce patient attrition from ART care in adolescents and youth, and was a low cost intervention with reasonable cost-effectiveness. Lastly, a published scientific letter is included as an appendix, which is a critique of findings from a cluster-randomized trial investigating the effectiveness of two interventions as part of the current South African National Adherence guidelines (AGL). The letter recommends the inclusion of long-term CBS for ART patients utilizing CHWs in a revised version of the AGL. The thesis concludes that task-shifting healthcare models including communitybased and pharmaceutical care models are effective and cost-efficient for HIV program delivery in South Africa, and can aid the greater Southern African regions’ progress toward several of the interrelated UNAIDS Sustainable Development Goals by 2030.
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    Optimisation and benchmarking of analytical approaches to estimation of population level HIV incidence from survey data
    (Stellenbosch : Stellenbosch University, 2022-04) Mhlanga, Laurette; Welte, Alex; Grebe, Eduard; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Global Health. Epidemiology and Biostatistics.
    ENGLISH SUMMARY: Disease prevalence (the proportion of a population with a condition of interest) is conceptually and procedurally much more straightforward to estimate than disease incidence (the rate of occurrence of new cases - for example, infections). For long-lasting conditions, incidence is fundamentally more difficult to estimate than prevalence, but also more interesting, as it sheds light on current epidemiological trends such as the emerging burden on health systems and the impact of recent policy interventions. Progress towards reducing reliance on questionable assumptions in the analysis of large population based surveys (for the estimation of HIV incidence) has been slow. The work of Kassanjee et al and the work of Mahiane et al, in particular, provide rigorous ways of estimating incidence by using 1) markers of ‘recent infection’, 2) the ‘gradient’ of prevalence, and 3) ‘excess mortality’ associated with HIV infection, without the need for simplifying assumptions to the effect that any particular parameters are constant over ranges of time and/or age. To date, the use of these methods has largely ignored 1) the rich details of the age and time structure of survey data, and 2) the opportunities for combining the two methods. The primary objective of this work was to find stable approaches to applying the Mahiane and Kassanjee methods to large age/time structured population survey data sets which include HIV status, and optionally, ‘recent infection’ status. In order to evaluate proposed methods, a sophisticated simulation platform was created to simulate HIV epidemics and generate survey data sets that are structured like real population survey data, with the underlying incidence, prevalence, and mortality explicitly known. The first non-trivial step in the analysis of survey data amounts essentially to performing a smoothing procedure from which the (age/time specific) prevalence of HIV infection, the prevalence of ‘recent infection’, and the gradient of prevalence of infection can be inferred without recourse to ‘epidemiological’ assumptions. The second step involves the correct accounting for uncertainty in a context-specific weighted mean of the Mahiane and Kassanjee estimators. These two steps are approached incrementally, as there are numerous details which have not previously been systematically elucidated. The investigation culminates in a proposed generic ‘once size fits most’ algorithm based on: 1) fitting survey data to generalised linear models defined by simple link functions and high order polynomials in age and time; 2) the use of a ‘moving window’ rule for data inclusion into a separate analysis for each age/time point for which incidence is to be estimated; 3) a ‘variance optimal’ weighting scheme for the combination of the Mahiane and Kassanjee estimators (when both are applicable); 4) flexible use of a delta method expansion or bootstrapping to estimate confidence intervals and p values. We find it is relatively easy to obtain estimates with practically negligible bias, but samplesizes/ sampling-density requirements are always considerable. We also make numerous observations on survey design and the inherent challenges faced by all attempts to estimate HIV incidence using surveys of reasonable size.