The performance of the recombinase polymerase amplification test for detecting Leishmania deoxyribonucleic acid from skin lesions of patients with clinical or epidemiological suspicion of cutaneous leishmaniasis

Abstract

Background: The diagnosis of cutaneous leishmaniasis (CL) is based on demonstration of the presence of the parasite in samples obtained from the lesions by direct examination (DE), culture or polymerase chain reaction (PCR)-based molecular tests. Recombinase polymerase amplification (RPA) represents an isothermal version of the conventional PCR (cPCR) technique, being ideal for detecting Leishmania DNA, especially in field conditions.

Methods: A prospective and cross-sectional study was conducted to evaluate the diagnostic performance of RPA in the health centres of rural endemic sites or the evaluation centre (EC) of 11 Colombian municipalities and in a reference centre (RC).

Results: Samples of 128 patients with suspected CL were included and processed for analysis by RPA vs DE in the EC and RPA vs DE and cPCR in the RC. The RPA performed at the EC was more sensitive (90.4% [95% confidence interval {CI} 81.9 to 95.7]) than the DE (42-67%) and the specificity was 72.7% (95% CI 57.2 to 85.0). Both the sensitivity and specificity increased to 100% when adjusting by the imperfect reference standard analysis method. In the RC, the sensitivity of RPA vs cPCR was 72% and the specificity was 69.8%, while the sensitivity of cPCR vs the DE test was 78.8% and the specificity was 81%.

Conclusions: The higher sensitivity and specificity shown by RPA in the EC, but also its ease and speed of use, justify performing RPA in the health centres of rural endemic sites. In addition, RPA eliminates the subjectivity inherent in the traditional DE.

Keywords: data accuracy; diagnosis; polymerase chain reaction; sensitivity; specificity.