SPECIES-SPECIFIC PCR DETECTION OF MALARIA PARASITES BY MICROTITER PLATE HYBRIDIZATION - CLINICAL-STUDY WITH MALARIA PATIENTS

A simple and convenient PCR method that amplifies the 18S rRNA genes h as been developed for the purpose of detecting and differentiating fou r species causing malaria in humans. The advantage of the assay is tha t the biotinylated PCR product is visualized following hybridization w ith specific probes which are immobilized on plate wells (microtiter p late hybridization). This method has been previously evaluated in a fi eld study and was found to be sensitive and specific for the detection of Plasmodium falciparum and Plasmodium vivax. In the current study, the microtiter plate hybridization PCR method was evaluated by using b lood specimens from malaria patients. All of 36 cases of falciparum ma laria, 26 of 27 cases of vivax malaria, all of 11 cases of ovale malar ia, and 2 cases of malariae malaria were diagnosed species specificall y by the PCR method, There were four smear-negative, PCR-positive case s that seemed to correspond to the convalescent stage of malaria. In c ontrast, 30 cases for which the diagnosis of malaria has been excluded on the basis of microscopy and clinical courses showed negative PCR r esults. By comparing parasite densities and PCR results following anti malarial treatment of some patients, it was revealed that the PCR resu lts largely paralleled the parasite densities and that PCR could detec t as few as 10 parasites per mu l of blood. We conclude that this PCR method is highly sensitive and specific for the detection of all four parasite species and can serve as a useful supplement to microscopy fo r the clinical management of malaria.