Detection and Species Identification of Malaria Parasites by Nested-PCR: Comparison with Light Microscopy and with SD BIOLINE Malaria Ag Test in Luanda, Angola

Abstract

Background: Malaria is the infectious disease causing the highest morbidity and mortality in Angola. Existing tools for the diagnosis of malaria include microscopy, rapid diagnosis tests (RDTs) and molecular tools. Nested-PCR is commonly used as a reference technique in the diagnosis of malaria due to its high sensitivity and specificity. The present study aims to evaluate the accuracy of light microscopy and SD BIOLINE Malaria Ag in the detection of Plasmodium spp. infection, using the nested-PCR as a reference method, and to determine the Plasmodium species in the study populations (Luanda, Angola) using this molecular tool. Methods: Blood samples were obtained from patients with clinical suspicion of malaria. Malaria was diagnosed by light microscopy, SD BIOLINE Malaria Ag and nested-PCR, used as a reference method, with Plasmodium falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi being detected when possible. The sensitivity, specificity, positive, and negative predictive values (PPV and NPV) of microscopy and SD BIOLINE Malaria Ag were compared using the McNemar’s test and the weighted generalized score Chi-squared test for paired data. Results: A total of 225 subjects were studied. SD BIOLINE Malaria Ag was significantly more sensitive than microcopy (87.65% versus 71.60%), and was substantially correlated (κ = 0.64) with the reference method. Nested-PCR detected 36.0% (81/225) cases, 80 cases (98.8%) infected with P. falciparum and 1 case as P. malariae (1.2%), with no mixed infections. Conclusion: The findings of this study support the need to use RDT in the diagnosis of Plasmodium. PCR could appear to be a useful method for detecting Plasmodium parasites during active malaria surveillance in Angola. This study contributes to wide knowledge about the presence of Plasmodium species in Angola.