The performance and utility of rapid diagnostic assays for Plasmodium falciparum malaria in a field setting in the Lao People's Democratic Republic.

Rapid diagnostic assays for malaria have the potential to improve the management and control of the disease in developing countries. The objectives of the present study were to evaluate, in a field setting, the performance of several such assays for Plasmodium falciparum infection and to examine the usefulness of these assays in identifying subjects for treatment trials in rural field sites. Residents of 12 villages in Laos who presented with fever were eligible for inclusion. Blood was collected by fingerprick for a dipstick assay, developed by the Program for Appropriate Technology in Health (PATH), performed and interpreted in the field by local healthcare workers. Compared with 'blinded' reference microscopy (N =196), the sensitivity and specificity of the PATH assay were 96.2% and 93.0%, respectively. Two rapid diagnostic assays (PATH and OptiMAL) were also performed on the subset of subjects eligible to participate in an in-vivo treatment trial (N = 97), and the results again compared with those of 'blinded' reference microscopy. In this subset, a subject was considered a 'true positive' if found positive by microscopy or the alternate rapid assay. Using this modified reference standard, the sensitivity and specificity of the PATH assay were 96.7% and 94.4%, and those of the OptiMAL assay were 91.8% and 100%, respectively. Both of the rapid assays tested therefore appear suitable for use in rural field settings by local healthcare providers and can accurately identify participants for treatment trials.

Effects of viral hemorrhagic fever inactivation methods on the performance of rapid diagnostic tests for Plasmodium falciparum.

Blood samples from patients with viral hemorrhagic fever (VHF) pose a serious risk to laboratory workers. Current contingency plans for VHF samples recommend the use of heat, gamma-irradiation, or Triton X-100 to inactivate samples before handling. Malaria is the most important alternative diagnosis to be excluded in cases of suspected VHF. Interpretation of malaria smears using samples inactivated with these methods is problematic because morphology is altered. The objective of this study was to assess the impact of different inactivation methods on the performance of rapid diagnostic tests for Plasmodium falciparum. Triton X-100 and gamma-irradiation of samples preserved detection. The impact of Triton X-100 inactivation was also "blindly" evaluated using 100 blood samples from febrile travelers. Triton X-100 inactivation of samples did not significantly affect the performance of these tests. This may represent a useful strategy for excluding the diagnosis of falciparum malaria in cases of suspected VHF.