Use of rapid diagnostic tests in malaria school surveys in Kenya: does their under-performance matter for planning malaria control?

Abstract

Malaria rapid diagnostic tests (RDTs) are known to yield false-positive results, and their use in epidemiologic surveys will overestimate infection prevalence and potentially hinder efficient targeting of interventions. To examine the consequences of using RDTs in school surveys, we compared three RDT brands used during a nationwide school survey in Kenya with expert microscopy and investigated the cost implications of using alternative diagnostic approaches in identifying localities with differing levels of infection. Overall, RDT sensitivity was 96.1% and specificity was 70.8%. In terms of classifying districts and schools according to prevalence categories, RDTs were most reliable for the < 1% and > 40% categories and least reliable in the 1-4.9% category. In low-prevalence settings, microscopy was the most expensive approach, and RDT results corrected by either microscopy or polymerase chain reaction were the cheapest. Use of polymerase chain reaction-corrected RDT results is recommended in school malaria surveys, especially in settings with low-to-moderate malaria transmission.

Figure 1.

Association between school level microscopy-corrected rapid diagnostic test (RDT) prevalence and RDT only prevalence in school malaria surveys in Kenya, 2008–2010. The black solid line indicates the microscopy-corrected RDT prevalence and the horizontal gray bars indicate the RDT only prevalence. Vertical dashed lines represent the prevalence classes (0–0.9%, 1–4.9%, 5–39.9%, and > 40%).

Figure 2.

Relationship between surveys costs and prevalence of Plasmodium spp. infection according to A, alternative microscopy and rapid diagnostic test (RDT) approaches and B, alternative polymerase chain reaction (PCR) plus RDT approaches, during school malaria surveys in Kenya, 2008–2010. The RDT costs are based on the cost of Paracheck Pf device.