Doctoral Degrees (Epidemiology and Biostatistics)

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Browsing Doctoral Degrees (Epidemiology and Biostatistics) by browse.metadata.advisor "Nachega, Jean"

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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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    Evaluation of the Mean Duration of Recent Infection (MDRI) and the False Recent Rate (FRR) for the Limiting Antigen Avidity Enzyme Immune Assay (LAg) and Bio-Rad HIV ½ Plus O Avidity Incidence Assay (BRAI)
    (Stellenbosch : Stellenbosch University, 2017-12) Gonese, Elizabeth; Hargrove, John; Nachega, Jean; Van Zyl, Gert; Kilmarx, Peter H.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Global Health. Epidemiology and Biostatistics.
    ENGLISH SUMMARY : Background: The evaluation of laboratory assays in estimating HIV incidence has become a priority because of the complexity of HIV epidemics and the need to measure the impact of public health interventions targeting reduction of HIV incidence. Biomarkers should have test properties that allow the lowest possible False Recent Rate (FRR, or probability of diagnosing a long-term infection as recently infected) over the longest possible period (Mean Duration of Recent Infection or MDRI) during which the case is considered as a recent infection. Methods: We compared the BED Capture Enzyme Immunoassay (BED), Sedia Limiting Antigen (LAg) and Bio-Rad HIV ½ Plus O Avidity Incidence Assay (BRAI) using samples from a prospective cohort trial, the Zimbabwe Vitamin A for Mothers and Babies Project (ZVITAMBO) 1997–2000. We determined MDRI using 591 samples from 184 seroconverting women, and determined FRR by testing 2825 cases known to be HIV- positive for >12 months. We used these results to estimate HIV incidence over the first 12 months postpartum, and during the period prior to childbirth. Results: At recommended cut-offs MDRI values were: BRAI, 135 days (120 – 151) at Avidity Index (AI) 30%; LAg, 104 days (98 - 110) at ODn cut-off 1.5; BED, 188 days (180 -196) at ODn cut-off 0.8. All error bounds in this thesis signify 95% confidence intervals. The coefficients of variation (CV) of the MDRI estimates for BRAI, LAg and BED were 5.9%, 2.9% and 2.1%, respectively. Corresponding FRRs were 1.1% (0.7-1.5) for BRAI, 0.6% (0.3-0.9) for LAg and 4.8% (4.1-5.7) for BED. MDRI and FRR estimates, all derived using postpartum women, were lower than in other published studies. Using original ZVITAMBO HIV diagnoses, adjusted HIV incidence over the first 12 months postpartum was estimated as; BRAI, 2.7% (1.8-3.7); LAg, 3.7% (2.7-4.8); BED, 3.6% (2.4 -4.9). Follow-up incidence was 3.4% (3.0-3.8). When cases with viral load <1000 copies/ml were defined as long-term infections, regardless of serological biomarker level, FRRs were; BRAI, 1.0% (0.7-1.5); LAg, 0.2% (0.2 -0.7); BED 3.8% (3.1-4.6). MDRIs were; BRAI, 133 days (113-154); LAg, 101 days (87-115); BED, 177 days (155 - 199). Corresponding incidences, unadjusted for FRR, were: BRAI, 3.9% (2.9-4.9); LAg, 3.1% (2.1-4.0); BED, 6.2 % (5.0-7.3). Adjusted estimates were 2.7% (1.5-4.0), 2.5% (1.6-3.5) and 2.6% (1.6-3.7) respectively. At baseline, with no follow-up estimate for comparison, adjusted incidence for serological biomarkers used alone were; BRAI, 8.1% (6.6-9.7); LAg, 6.9% (5.7-8.1); BED 6.7% (5.5-7.9). When viral load was also used, the adjusted and unadjusted incidence estimates were; BRAI, 7.3% (5.7-8.8) and 8.4% (6.8-10.0); LAg, 5.1% (3.9-6.3) and 5.7% (4.5-6.9); BED, 5.4% (4.1-6.7) and 8.6% (7.3-10.0). Conclusion: At recommended cut-offs; BRAI FRR was 1.9 times higher than that of LAg. BRAI MDRIs were also 1.3 times higher, but with a relative standard error 2.4 times as high. Postpartum BRAI incidence estimates were consistently lower than follow-up estimates. Adjusted biomarker estimates under-estimated follow-up incidence when we used viral load in combination with either serological test.