Evaluation of the SD FK70 malaria Ag Plasmodium vivax rapid diagnostic test in a non-endemic setting.
BACKGROUND
For clinical and epidemiological reasons, it is interesting to diagnose non-falciparum malaria to the species level. This retrospective study assessed the performance of the SD BIOLINE Malaria Antigen Pv test (FK70), a two-band immunochromatographic test detecting Plasmodium vivax-specific lactate dehydrogenase, on samples of international travellers in a non-endemic setting.


METHODS
Stored blood samples from international travellers suspected of malaria were used, with microscopy corrected by PCR as the reference method. Samples infected by Plasmodium vivax (n = 100), Plasmodium falciparum (n = 75), Plasmodium ovale (n = 75) and Plasmodium malariae (n = 25) were included, as well as 100 malaria-negative samples. End points were sensitivity, specificity, inter-reader reliability and reproducibility.


RESULTS
The overall sensitivity of the FK70 for the diagnosis of P. vivax was 88.0% (95% confidence interval (CI): 83.6% - 90.3%). For parasite densities > 500/microl, a sensitivity of 97.2% (CI: 92.6% - 99.1%) was obtained. Specificity was 98.5%, with 4 out of 75 P. falciparum samples testing positive. None of the P. ovale samples tested positive. Nearly two-thirds (57/88, 64.7%) of positive P. vivax samples showed faint or weak line intensities, with stronger line intensities at higher parasite densities. The test showed excellent reproducibility and reliability for test results and line intensities (kappa values exceeding 0.98 and 0.87 respectively).


CONCLUSIONS
The FK70 test performed well in diagnosing P. vivax infections in a non-endemic reference setting. It can be of added value to microscopy in species differentiation of malaria infections, especially at parasite densities > 500/microl.
Gillet
Philippe
P
Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium. pgillet@itg.be
Bosselaers
Katrien
K
Cnops
Lieselotte
L
Bottieau
Emmanuel
E
Van Esbroeck
Marjan
M
Jacobs
Jan
J
D000818:Animals; D000953:Antigens, Protozoan / Q000302:isolation & purification; D003955:Diagnostic Tests, Routine / Q000379:methods*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007770:L-Lactate Dehydrogenase / Q000302:isolation & purification; D016780:Malaria, Vivax / Q000175:diagnosis*; D015588:Observer Variation; D010966:Plasmodium vivax / Q000302:isolation & purification*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
D000953:Antigens, Protozoan; D007770:L-Lactate Dehydrogenase