Evaluation of a density-based rapid diagnostic test for sickle cell disease in a clinical setting in Zambia.

Although simple and low-cost interventions for sickle cell disease (SCD) exist in many developing countries, child mortality associated with SCD remains high, in part, because of the lack of access to diagnostic tests for SCD. A density-based test using aqueous multiphase systems (SCD-AMPS) is a candidate for a low-cost, point-of-care diagnostic for SCD. In this paper, the field evaluation of SCD-AMPS in a large (n = 505) case-control study in Zambia is described. Of the two variations of the SCD-AMPS used, the best system (SCD-AMPS-2) demonstrated a sensitivity of 86% (82-90%) and a specificity of 60% (53-67%). Subsequent analysis identified potential sources of false positives that include clotting, variation between batches of SCD-AMPS, and shipping conditions. Importantly, SCD-AMPS-2 was 84% (62-94%) sensitive in detecting SCD in children between 6 months and 1 year old. In addition to an evaluation of performance, an assessment of end-user operability was done with health workers in rural clinics in Zambia. These health workers rated the SCD-AMPS tests to be as simple to use as lateral flow tests for malaria and HIV.

The cost-effectiveness of cotrimoxazole prophylaxis in HIV-infected children in Zambia.

OBJECTIVE: To assess the cost-effectiveness of cotrimoxazole prophylaxis in HIV-infected children in Zambia, as implementation at the local health centre level has yet to be undertaken in many resource-limited countries despite recommendations in recent updated World Health Organization (WHO) guidelines. DESIGN: A probabilistic decision analytical model of HIV/AIDS progression in children based on the CD4 cell percentage (CD4%) was populated with data from the placebo-controlled Children with HIV Antibiotic Prophylaxis trial that had reported a 43% reduction in mortality with cotrimoxazole prophylaxis in HIV-infected children aged 1-14 years. METHODS: Unit costs (US$ in 2006) were measured at University Teaching Hospital, Lusaka. Cost-effectiveness expressed as cost per life-year saved, cost per quality adjusted life-year (QALY) saved, cost per disability adjusted life-year (DALY) averted was calculated across a number of different scenarios at tertiary and primary healthcare centres. RESULTS: : Cotrimoxazole prophylaxis was associated with incremental cost-effectiveness ratios (ICERs) of US$72 per life-year saved, US$94 per QALY saved and US$53 per DALY averted, i.e. substantially less than a cost-effectiveness threshold of US$1019 per outcome (gross domestic product per capita, Zambia 2006). ICERs of US$5 or less per outcome demonstrate that cotrimoxazole prophylaxis is even more cost-effective at the local healthcare level. The intervention remained cost-effective in all sensitivity analyses including routine haematological and CD4% monitoring, varying starting age, AIDS status, cotrimoxazole formulation, efficacy duration and discount rates. CONCLUSION: Cotrimoxazole prophylaxis in HIV-infected children is an inexpensive low technology intervention that is highly cost-effective in Zambia, strongly supporting the adoption of WHO guidelines into essential healthcare packages in low-income countries.

Use of dried whole blood spots to measure CD4+ lymphocyte counts in HIV-1-infected patients.

As antiretroviral drugs become widely available in developing countries, practical, field-friendly, and cheap methods of measuring CD4+ lymphocyte counts need to be developed. We tested use of whole blood spots dried on filter paper to measure CD4+ lymphocyte counts. We obtained blood from 42 HIV-1-infected patients from Zambia. We dried blood spots on filter paper and measured CD4+ lymphocyte counts with an established commercial enzyme immunoassay. We compared these measurements with those obtained from matched liquid whole-blood samples analysed with standard flow cytometry. Results of the filter-paper method accorded well with flow cytometry CD4 counts greater than 200 cells/microL (mean difference 13.6 [SD 52.4]). Dried whole blood stored on filter paper could be developed into a field-friendly alternative for CD4+ lymphocyte count measurements.