Field evaluation of simplified radioactive and nonradioactive DNA probe methods for the diagnosis of falciparum malaria.

Specific DNA probe hybridization technique is one method of choice for detection of malaria infection. It provides an obvious advantage over conventional microscopy when large numbers of samples are simultaneously monitored. The method was simplified so that preparation and processing of blood specimens were all performed on membrane filters. Background signals generated from blood components were removed by treating samples spotted on the membrane with a series of buffer washes without the necessity of a protease digestion step. Hybridization was monitored using either 32P-or digoxigenin-labeled DNA probe. 849 field samples collected from various malaria endemic areas in Thailand have been evaluated by this protocol and compared with microscopic examination. Sensitivity obtained by this procedure was comparable to that of microscopy at a malaria clinic. The specificities of both types of DNA probes were better than 93%, but digoxigenin-labeled probe performed better than 32P-labeled one when the numbers of parasites were less than 25 per 200 white blood cells.