Test characteristics of two rapid antigen detection tests (SD FK50 and SD FK60) for the diagnosis of malaria in returned travellers

<p>Abstract</p> <p>Background</p> <p>Two malaria rapid diagnostic tests were evaluated in a travel clinic setting: the SD FK50 Malaria Ag <it>Plasmodium falciparum </it>test (a two-band test) and the SD FK60 Malaria Ag <it>P. falciparum</it>/Pan test (a three-band test).</p> <p>Methods</p> <p>A panel of stored whole blood samples (n = 452 and n = 614 for FK50 and FK60, respectively) from returned travellers was used. The reference method was microscopy with PCR in case of discordant results.</p> <p>Results</p> <p>For both tests, overall sensitivity for the detection of <it>P. falciparum </it>was 93.5%, reaching 97.6% and 100% at parasite densities above 100 and 1,000/μl respectively. Overall sensitivities for <it>Plasmodium vivax, Plasmodium ovale </it>and <it>Plasmodium malariae </it>for the FK60 test were 87.5%, 76.3% and 45.2%, but they reached 92.6% and 90.5% for <it>P. vivax </it>and <it>P. ovale </it>at parasite densities above 500/μl. Specificities were above 95% for all species and both tests when corrected by PCR, with visible histidine-rich protein-2 lines for <it>P. malariae </it>(n = 3) and <it>P. vivax </it>and <it>P. ovale </it>(1 sample each). Line intensities were reproducible and correlated to parasite densities. The FK60 tests provided clues to estimate parasite densities for <it>P. falciparum </it>below or above 1,000/μl.</p> <p>Conclusion</p> <p>Both the FK50 and FK60 performed well for the diagnosis of <it>P. falciparum </it>in the present setting, and the FK60 for the diagnosis of <it>P. vivax </it>and <it>P. ovale </it>at parasite densities > 500/μl. The potential use of the FK60 as a semi-quantitative estimation of parasite density needs to be further explored.</p