PIMATM point-of-care testing for CD4 counts in predicting antiretroviral initiation in HIV-infected individuals in KwaZulu-Natal, Durban, South Africa

Abstract

Introduction: Limited information is available on the usefulness of the PIMATM analyser in predicting antiretroviral treatment eligibility and outcome in a primary healthcare clinic setting in disadvantaged communities in KwaZulu-Natal, South Africa.

Materials and methods: The study was conducted under the eThekwini Health Unit, Durban, KwaZulu-Natal. Comparison of the enumeration of CD4+ T-cells in 268 patients using the PIMATM analyser and the predicate National Health Laboratory Services (NHLS) was undertaken during January to July 2013. Bland-Altman analysis to calculate bias and limits of agreement, precision and levels of clinical misclassification at various CD4+ T-cell count thresholds was performed.

Results: There was high precision of the PIMA^TM control bead cartridges with low and normal CD4+ T-cell counts using three different PIMA^TM analysers (%CV < 5). Under World Health Organization (WHO) guidelines (≤ 500 cells/mm³), the sensitivity of the PIMATM analyser was 94%, specificity 78% and positive predictive value (PPV) 95%. There were 24 (9%) misclassifications, of which 13 were false-negative in whom the mean bias was 149 CD4+ T-cells/mm³. Most (87%) patients returned for their CD4 test result but only 67% (110/164) of those eligible (≤ 350 cells/mm³) were initiated on antiretroviral therapy (ART) with a time to treatment of 49 days (interquartile range [IQR], 42–64 days).

Conclusion: There was adequate agreement between PIMA^TM analyser and predicate NHLS CD4+ T-cell count enumeration (≤ 500 cells/mm³) in adult HIV-positive individuals. The high PPV, sensitivity and acceptable specificity of the PIMA^TM analyser technology lend it as a reliable tool in predicting eligibility and rapid linkage to care in ART programmes.

Keywords: HIV; Point of Care; PIMATM CD4+ T cell counts; antiretroviral therapy; prediction/eligibility; South Africa