Comparison of optimal malarial test with light microscopy for the diagnosis of malaria

To evaluate the efficacy of a parasite lactate dehydrogenase-based immunochromatographic antigen detection assay (optimal) against conventional light microscopy in the diagnosis of malaria at Military Hospital, Rawalpindi and Department of Pathology Army Medical College Rawalpindi from August to October 2002 in patients reporting sick with history suggestive of malaria.

The blood samples were collected from 215 patients reporting with symptoms suggestive of malaria. Thick and thin blood films were prepared, stained with Leishman's stain and examined by light microscopy for the presence of malarial parasites. Parasitaemia was estimated on all positive slides. All samples were tested for presence of malarial parasite by optimal dipstick method according to the manufacturer's instructions.

A total of 215 cases were studied. Malarial parasites were visualized in 98 (45.5%) cases with light microscopy. Optimal test revealed 93 (43.2%) of these samples as positive. Microscopy showed 61 out of 98 positive cases to be P. vivax and 37 P. falciparum. The Optimal dipstick method revealed that 58 out of 93 were positive for P. vivax and 35 positive for P. falciparum. These results demonstrated that Optimal had sensitivities of 95% and 94.5% for P. vivax and P. falciparum respectively. It has 100% specificity for both malarial species, when compared to conventional microscopy.

Optimal test showed excellent correlation with microscopy in the diagnosis of P. vivax and P. falciparum. It is expensive but it has an advantage of being simple, rapid and effective test in the diagnosis of malaria especially where well trained microscopists are not available or work load is too high.