Treatment assessment by monitoring parasite load in skin biopsies from patients with cutaneous leishmaniasis, using quantitative nucleic acid sequence‐based amplification

Summary Background.  Current diagnostic methods for cutaneous leishmaniasis (CL) have low sensitivity or are not useful for treatment follow‐up. We previously described the quantitative nucleic acid sequence‐based amplification (QT‐NASBA) method as a sensitive and specific assay for detection and quantification of Leishmania parasites in skin biopsies. This assay could be a valuable instrument for monitoring response to treatment of CL and identifying treatment failures at an early stage. Aim.  QT‐NASBA results of skin biopsies at the end and 6 weeks after treatment from patients with proven CL on various treatment regimens were compared with clinical outcome. Methods.  The QT‐NASBA assay measured the parasite load in skin biopsies before, at the end and 6 weeks after treatment. The results were compared with treatment outcome (clinical cure, delayed healing response or treatment failure) up to 6 months after treatment. Results.  In total, 137 skin biopsies were obtained from 53 patients. A positive QT‐NASBA result 6 weeks after treatment was significantly associated with treatment failure/delayed healing up to 6 months ( P  < 0.001). The positive predictive value (PPV) was 100% and the negative predictive value (NPV) was 92% (95% CI 82–100%). QT‐NASBA results at the end of treatment and clinical outcome showed a less significant association ( P  < 0.05), with a PPV of 46% (95% CI 16–75% and an NPV of 89% (95% CI 79–99%). Conclusions.  The QT‐NASBA assay is a useful instrument to monitor parasite load in skin biopsies of patients with CL 6 weeks after treatment and can help to predict clinical outcome.