Malaria diagnosis and treatment under the strategy of the integrated management of childhood illness (IMCI): relevance of laboratory support from therapid immunochromatographic tests of ICT Malaria P.f/P.v and OptiMal

The algorithm developed for the integrated management of childhood illness (IMCI) provides guidelines for the treatment of paediatric malaria. In area s where malaria is endemic, for example, the IMCI strategy may indicate tha t children who present with fever, a recent history of fever and/or pallor should receive antimalarial chemotherapy. In many holo-endemic areas, it is unclear whether laboratory tests to confirm that such signs are the result of malaria would be very relevant or useful. Children from a holo-endemic region of Tanzania were therefore checked for malarial parasites by microsc opy and by using two rapid immunochromatographic tests (RIT) for the diagno sis of malaria (ICT Malaria P.f/P.v and OptiMal(R)). At the time they were tested, each of these children had been targeted for antimalarial treatment (following the IMCI strategy) because of fever and/or pallor. Only 70% of the 395 children classified to receive antimalarial drugs by th e IMCI algorithm had malarial parasitaemias (68.4% had Plasmodium falciparu m trophozoites, 1.3% only P. falciparum gametocytes, 0.3% P. ovale and 0.3% P. malariae). As indicators of P. falciparum trophozoites in the periphera l blood, fever had a sensitivity of 93.0% and a specificity of 15.5% wherea s pallor had a sensitivity of 72.2% and a specificity of 50.8%. The RIT bot h had very high corresponding sensitivities (of 100.0% for the ICT and 94.0 % for OptiMal) but the specificity of the ICT (74.0%) was significantly low er than that for OptiMal (100.0%). Fever and pallor were significantly asso ciated with the P. falciparum asexual parasitaemias that equalled or exceed ed the threshold intensity (2000/mul) that has the optimum sensitivity and specificity for the definition of a malarial episode. Diagnostic likelihood ratios (DLR) showed that a positive result in the Opt iMal test (DLR=infinity) was a better indication of malaria than a positive result in the ICT (DLR=3.85). In fact, OptiMal had a diagnostic reliabilit y (0.93) which approached that of an ideal test and, since it only detects live parasites, OptiMal is superior to the ICT in monitoring therapeutic re sponses. Although the RIT may seem attractive for use in primary health fac ilities because relatively inexperienced staff can perform them, the high c ost of these tests is prohibitive. In holo-endemic areas, use of RIT or mic roscopical examination of bloodsmears may only be relevant when malaria nee ds to be excluded as a cause of illness (e.g. prior to treatment with toxic or expensive drugs, or during malaria epidemics). Wherever the effective d rugs for the first-line treatment of malaria are cheap (e.g. chloroquine an d Fansidar), treatment based on clinical diagnosis alone should prove cost- saving in health facilities without microscopy.