Evaluation of two tests based on the detection of histidine rich protein 2 for the diagnosis of imported Plasmodium falciparum malaria.

The ParaSight-F dipstick test (Becton Dickinson, USA) and the ICT Malaria Pf test (ICT, Australia) both detect histidine rich protein 2 (HRP-2), a water-soluble antigen expressed by Plasmodium falciparum trophozoites. The present study compared the diagnostic performance of both tests in persons returning to Belgium from countries endemic for malaria. During a period of 18 months both tests were performed on all patients returning from the tropics with a positive malaria blood film. Patients with fever without an obvious cause were used as controls. For the ParaSight-F test, considering P. falciparum trophozoites only, sensitivity was 95% and specificity 90%. Considering trophozoites of all species of Plasmodium, sensitivity was 71% and specificity 87%. Finally, considering patients with clinical malaria, the sensitivity of the test was 72% and specificity 87%. For the ICT Malaria Pf test, sensitivity was 95% and specificity 89% for P. falciparum trophozoites only, 71% and 86% for trophozoites of all species, and 72% and 87% for clinical malaria. Both tests gave highly comparable results. However, antigen detection assays cannot replace conventional microscopy in diagnosing imported malaria. Thick blood film examination is more sensitive and more specific, it allows estimation of parasitaemia and distinction between parasite growth stages, and it covers all species. Moreover, with treated patients the use of antigen tests might lead to problems in determining the efficacy of therapy.