Rapid Diagnostic Test Evaluated for Human Malaria Species

A rapid diagnostic test (RDT) for malaria parasites has been evaluated and compared with other methods in a reference setting.

The three-band rapid diagnostic test detects Plasmodium falciparum-specific parasite lactate dehydrogenase (Pf-pLDH) and pan Plasmodium-specific pLDH (pan-pLDH).

Scientists at Maastricht University (Netherlands) carried out a retrospective and a prospective study to assess with 498 stored and 77 fresh blood samples obtained from international travelers suspected of malaria. Both panels comprised all four Plasmodium species; the retrospective panel comprised also samples negative for malaria. The retrospective panel had been obtained between February 1996 and May 2011. The reference method was microscopy corrected by polymerase chain reaction (PCR). The prospective panel was run side-to-side with two other RDTs.

In the retrospective evaluation, overall sensitivity for the 247 P. falciparum samples was 94.7%, reaching 98.7% for parasite densities greater than 1,000/μL. Most false negative results occurred among samples with pure gametocytaemia and at parasite densities less than or equal to 100/μL. None of the 96 negative samples showed visible test lines. Sensitivities for the 70 P. vivax, 69 P. ovale and 16 P. malariae were 74.3%, 31.9% and 25.0% respectively. Overall, Pf-pLDH test lines showed higher line intensities compared to the pan-pLDH lines, with 67.9% and 23.0% medium and strong line intensities for P. falciparum.

In the prospective panel, the CareStart pLDH RDT (AccessBio Inc.; Monmouth, NJ, USA) showed higher sensitivities for P. falciparum compared to OptiMAL (Pf-pLDH/pan-pLDH, BioRad; Marnes-la-Coquette, France) and lower sensitivities for P. falciparum as compare to SDFK60 (histidine-rich protein-2 (HRP-2)/pan-pLDH; Standard Diagnostics; Hagal-Dong, Korea). Wrong species identification occurred in 10 (2.5%) samples and was mainly due to P. vivax samples reacting with the Pf-pLDH test line.

The authors concluded that CareStart pLDH may be an alternative to other well-described HRP-2 three band RDTs in the diagnostic setting in non-endemic areas. Despite being better than the other two RDTs that were run side by side, it should be noted that its performance for the detection of P. ovale and P. malariae is mediocre. The study was published on June 18, 2012, in the Malaria Journal.

Related Links:
Maastricht University
AccessBio Inc.
BioRad