Comparison of blood-film microscopy, the OptiMAL (R) dipstick, Rhodamine-123 fluorescence staining and PCR, for monitoring antimalarial treatment

In an attempt to see if the OptiMAL(R) dipstick (Flow Inc., Portland, OR) c an be used to monitor antimalarial treatment, a pilot study of 17 patients with Plasmodium falciparum malaria, admitted to the Hospital for Tropical D iseases in London, U.K., was conducted. Sequential, follow-up, blood specim ens were obtained from day 1 to day 3, 4 or 5 post-admission. Thin and thic k films prepared from these samples were examined for the presence of malar ial parasites, and the intensities of parasitaemia were estimated. In addit ion, each specimen was tested with the OptiMAL dipstick, Rhodamine-123 fluo rescence staining and, on specimens collected on day 1 and the last follow- up before discharge, by a PCR-based test. The results showed that OptiMAL has good sensitivity for the initial diagno sis of P. falciparum malaria and also mirrors the decline in viability of t he parasites on treatment, giving the potential to follow the efficacy of d rug treatment. The results of the PCR-based tests were still positive when the blood film and OptiMAL result were negative. The OptiMAL dipstick compa red well with blood-film microscopy for monitoring antimalarial treatment a nd could be a useful replacement for microscopy to monitor treatment in pla ces where facilities for microscopy are either lacking or inadequate. In de veloped countries it could be a useful adjunct to blood-film microscopy, an d it might permit a reduction in the duration of hospitalization and give a n early warning of treatment failure.