Performance of a new gelled nested PCR test for the diagnosis of imported malaria: comparison with microscopy, rapid diagnostic test, and real-time PCR

Microscopy and rapid diagnostic tests (RDTs) are the techniques commonly used for malaria diagnosis but they are usually insensitive at very low levels of parasitemia. Nested PCR is commonly used as a reference technique in the diagnosis of malaria due to its high sensitivity and specificity. However, it is a cumbersome assay only available in reference centers. We evaluated a new nested PCR-based assay, BIOMALAR kit (Biotools B&M Labs, Madrid, Spain) which employs ready-to-use gelled reagents and allows the identification of the main four species of Plasmodium. Blood samples were obtained from patients with clinical suspicion of malaria. A total of 94 subjects were studied. Fifty-two (55.3 %) of them were malaria-infected subjects corresponding to 48 cases of Plasmodium falciparum, 1 Plasmodium malariae, 2 Plasmodium vivax, and 1 Plasmodium ovale. The performance of the BIOMALAR test was compared with microscopy, rapid diagnostic test (RDT) (BinaxNOW® Malaria) and real-time quantitative PCR (qPCR). The BIOMALAR test showed a sensitivity of 98.1 % (95 % confidence interval [CI], 89.7–100), superior to microscopy (82.7 % [95 % CI, 69.7–91.8]) and RDT (94.2 % [95 % CI, 84.1–98.8]) and similar to qPCR (100 % [95 % CI, 93.2–100]). In terms of specificity, the BIOMALAR assay showed the same value as microscopy and qPCR (100 % [95 % CI, 93.2–100]). Nine subjects were submicroscopic carriers of malaria. The BIOMALAR test identified almost all of them (8/9) in comparison with RDT (6/9) and microscopy (0/9). In conclusion, the BIOMALAR is a PCR-based assay easy to use with an excellent performance and especially useful for diagnosis submicroscopic malaria.