Tropical Disease Unit, Division of Infectious Diseases, Department of Medicine, The Toronto Hospital and The University of Toronto, Department of Experimental Therapeutics, Walter Reed Army Institute of Research, Toronto, Ontario, Canada
Imported malaria is an increasing problem worldwide. A rapid and accurate test for Plasmodium falciparum infection would facilitate the diagnosis of malaria in the returned traveler. The ParaSight®F antigen capture assay (dipstick test) is a new diagnostic test for P. falciparum based on detection of circulating histidine-rich protein-2 antigen. We performed a blinded evaluation of this assay compared with microscopy and the polymerase chain reaction (PCR) for the detection of P. falciparum infection in 151 febrile travelers. Compared with the PCR, the dipstick test had a sensitivity of 88% and a specificity of 97%. The ability of the dipstick test to detect P. falciparum was similar with that of microscopy (88% versus 83%) since the species of Plasmodium in 14 of 133 malaria-infected patients could not be determined by microscopy due to low parasite numbers. The dipstick test was 40% sensitive for infections with < 50 parasites/µl, 89% with 50–100 parasites/µl, and ≥ 93% with > 100 parasites/µl. Circulating antigen was detectable in 68% of the patients seven days after initiation of treatment and in 27% at day 28. The dipstick test represents a simple and accurate test for the diagnosis of P. falciparum infection in the returned traveler.