Evaluation of methods for the laboratory diagnosis of malaria in Guyana

When 297 blood samples taken from patients attending a fever clinic in Georgetown Public Hospital were examined microscopically, after thick and thin blood films had been stained with Giemsa, one hundred and forty-two (47.8%) were microscopically positive for malaria. After processing the patient's serum, samples by the Indirect Fluorescent Antibody (IFA) technique, specific IgG and IgM antibodies were detected in 239 (81.3%) and 179 (60.1%), respectively, of the sera. Based on the microscopical findings, the IFAT gave positive predictive and negative values of 54.4% and 81.8% (IgG), and 57.5% and 67.8% (IgM), suggesting that the IgM would be more useful than the IgG in the diagnosis of current malaria. An odds ratio analysis showed that the presence of symptoms, IgG or IgM antibodies, as well as visits to endemic regions, could be good indicators of current malaria. Age and occupation were not. The microscopical method will continue to be the gold standard-the best available criterion for the validation of our tests-for diagnosis of acute malaria.