Evaluation of diagnostic methods of re-emerging malaria in Korean patients

Malaria is one of the most important parasitic diseases especially in tropical areas. Over 300 million people are affected and the condition causes 1-3 million deaths each year. It is transmitted by the bite of infected Anopheles mosquitoes. Although Korea was declared to be free of Malaria by the WHO in 1979, malaria re-emergence has been apparent since 1993 amongst soldiers located near the De-Militarized Zone (DMZ) in the northern part of the country. Conventional microscopic examination of thin and thick blood films demonstrates the presence of the parasite and thus this method has been used to confirm the diagnosis of malaria, but it is a labor-intensive procedure and relies upon subjective interpretation. To overcome these limitations, fast and reliable methods for malaria detection have been recently introduced. In this study, we compared three kinds of antibody detection kits and one biochemical test kit that determines the presence of Plasmodium lactate dehydrogenase (pLDH) with conventional peripheral blood smears. The antibody detection methods examined were, two rapid test pack format methods and a single microplate format enzyme-linked immunosorbent assay (ELISA) kit, as manufactured by Korean companies. The sensitivities of the three commercial antibody detection kits in the early stage of malaria were 70.8%, 77.4%, and 63.6%, their corresponding specificities 90.5%, 91.8%, and 80.9%, and their accuracies 87.6%, 87.0%, and 76.7%. The sensitivity and specificity of the pLDH assay were 100% apiece and the results were in 100% concordance with the microscopy of thick blood films. Thus, the pLDH assay may be used as an alternative for conventional microscopic blood film examination, especially in emergency situations when prompt treatment is necessary.