Diagnostic Usefulness of Five Malaria Rapid Diagnostic Kits Compared with Stained Blood Smear Microscopy

Abstract

Malaria is a major health challenge. The causative organisms are the plasmodium parasites which are transmitted to humans via infected female anopheles’ mosquitos. The gold standard for its diagnosis is light microscopy of stained blood films. This work determined the suitability of five types of malaria rapid diagnostic test (mRDT) kits; Carestart, First Response, SD Bioline, Meriscreen and NxTek as alternatives to microscopy. About 2ml venous blood was collected from each of 615 patients who showed symptoms of malaria. The blood samples were treated with the mRDKs and by microscopy using Giemsa, Leishman and Field’s stains. The results revealed that 535 (87%) had plasmodium parasites by light microscopy, while the five RDTs showed varying results. The percentage sensitivity, specificity, positive predictive values and negative predictive values were RDK 1 (89.5, 87.2, 97.9, 55.4), RDK 2 (92.6, 89.5, 98.3, 64.3), RDK 3 (90.1, 82.2, 97.1, 55.3), RDK 4 (89.1, 85.2, 97.6, 53.8) and RDK 5 (92.9, 83.0, 97.3, 63.6). The mean values were 90.8, 85.4, 97.7 and 58.1 respectively at 95% confidence level. False negative results in the RDTs were observed in low parasiteamia while false positive results were observed in some patients on medication, perhaps because of the presence of the malaria antigens after the parasites had been cleared from the blood stream. mRDKs are important alternatives to microscopy only in cases of emergencies and where facilities and trained personnel are not available. The results confirm the superiority of microscopy of stained smears to mRDKs.