Evaluation of parasite Lactate Dehydrogenase (pLDH) Assay (Optimal-it) for detection of malaria on Thai-Burmese border

Abstract

The performances of OptiMAL-IT (DiaMed, Switzerland) and Paracheck-Pf (Orchid Biomedical, Goa, India) malaria rapid tests were evaluated in symptomatic patients with uncomplicated falciparum malaria. The sensitivity, specificity, positive predictive and negative predictive values of the tests were calculated taking microscopy as the "gold standard". The sensitivity and specificity of OptiMAL-IT for the diagnosis of Plasmodium falciparum parasites were 88% and 92% respectively. For Plasmodium non-falciparum, the sensitivity was 65% and specificity was 99%. The sensitivity and specificity of Paracheck-Pf for Plasmodium falciparum was 90% and 96% respectively. For Plasmodium falciparum the sensitivity of both tests decreased markedly at parasitaemia <500 parasites/uL (0.01% of infected RBC). At parasitaemia <100 parasites/uL (0.002% infected RBC) the sensitivity was only 20% for both tests. The sensitivity of OptiMAL-IL for non-dalciparum species secreased markedly at parasitaemia <5000 parasites/uL (0.1% IRBC) and was only 10% at the parasitaemia less than 100 parasites/uL (<0.002% IRBC). The performances of both tests for Plasmodium falciparum detection were not significantly different (p>0.05).