Laboratory tests for malaria: a diagnostic conundrum?

Abstract

Objectives: To detect malarial parasites using the peripheral blood smear (PBS) and to compare the PBS with the immunochromatographic antigen test (i.e. OptiMAL and polymerase chain reaction (PCR)).

Methods: Six ml of blood was collected from each of 170 patients clinically suspected of having malaria. These samples were used to perform PBS examination, the OptiMAL test and PCR by standard protocol.

Results: PBS examination found malarial parasites in 86 (50.6%) samples. In comparison, 71 (41.8%) samples were positive by OptiMAL test whereas PCR could detect malarial parasites in only 44 (25.9%) samples. All 84 (49.4%) samples which were negative by PBS were negative by both OptiMAL and PCR. The sensitivity and specificity were respectively 85.54% and 100% for OptiMAL and 51.12% and 100% for PCR. CONCLUSION; Depending on the tests' operational feasibility, and the availability of adequate trained personnel, equipment and laboratory management systems, and considering its sensitivity and cost-effectiveness, peripheral blood smear remains the test of choice for malaria, especially in endemic areas.