The combined immuno-chromographic-malaria dipstick (ICT) for the rapid diagnosis of malaria detects both Plasmodium falciparum (P.f.)-specific, histidine-rich protein 2 (HRP-2) and a plasmodial aldolase expressed by all Plasmodium species pathogenic to humans. ICT was applied in 674 febrile returnees from malaria-endemic regions attending our Tropical Diseases Unit. Microscopy confirmed malaria in 69/674 cases, of whom 67/69 had returned from Africa or Madagascar, and 2/69 from the Caribbean. Monoparasitic P.f. infection occurred in 52/69, mixed infection was due to P.f.+ P. ovale (P.o.) in 3/69, and P.f.+P. malariae (P.m.) in 1/69 cases. Monoparasitic P. vivax (P.v.) infection occurred in 8/69 , P.o. in 3/69, and P.m. in 2/69 cases . Whereas a positive HRP-2 band on the test was a highly sensitive indicator for P.f. infection (52/52 patients; sensitivity 100%), this was not the case for a positive aldolase band (25/52 patients; sensitivity 48.1%). Sensitivity of aldolase band for non-falciparum plasmodia was even lower: aldolase was positive in only 3/8 (37.5%) of patients with vivax malaria, and in 0/5 cases with P.o.- or P.m. infection. Co-reaction of both bands occurred more frequently in patients with P.f. parasitaemia of > or =40,000/microl (20/25, 80.0%) as compared to patients with P.f. parasitaemia <40,000/microl (5/27, 18.5%; P<0.00005), and to patients with mixed infection (P.f.+ P.o., P.f.+ P.m.: 2/4, 50.0%; diff. n.s.). In our series, co-reaction of HRP-2 and aldolase indicated monoparasitic falciparum malaria with high P.f. parasitaemia, rather than mixed infection. Whereas the aldolase band is not a reliable qualitative marker for malaria, co-reaction of HRP-2 and aldolase band may have a potential for indicating high parasitaemia in falciparum malaria.

We determined the sensitivity and specificity of three rapid immunochromatographic malarial antigen detection test systems (RDTs) for the detection of Plasmodium falciparum and assessed the quality of follow-up results. ParaSight-F and ICT Malaria detect histidinerich protein-2 (HRP-2), whereas OptiMal detects plasmodial lactate dehydrogenase (pLDH). ParaSight-F performed with 95.1% sensitivity and 97.1% specificity (554 patients tested of whom 144 had falciparum malaria). ICT Malaria performed with 95.7% sensitivity and 99.2% specificity (718 patients tested of whom 184 had falciparum malaria). OptiMal performed with 76.2% sensitivity and 99.7% specificity (539 patients tested of whom 130 had falciparum malaria). In follow-up investigations, HRP-2 did not appear to be a useful antigen due to its long half-life, whereas pLDH offers a reasonable correlation with the presence of viable parasites in those cases initially detected. We therefore conclude that a combination of both antigens might be the best option for creating a reliable RDT for the diagnosis of falciparum malaria.

Plasmodium malariae is regarded as usually being susceptible to all anti-malarials whether applied for prophylaxis or treatment. We report on three cases of P. malariae infection which occurred 12-14 weeks after anti-malarial chemoprophylaxis or treatment with mefloquine or atovaquone/proguanil. The most likely explanation for the failure of mefloquine and atovaquone/proguanil to prevent quartan malaria occurring some months later is the insufficient effect on the particularly long-lasting pre-erythrocytic development stages of P. malariae.