Diagnostic accuracy of a new Leishmania PCR for clinical visceral leishmaniasis in Nepal and its role in diagnosis of disease

To develop a new PCR for Leishmania detection and to estimate its diagnostic accuracy in a visceral leishmaniasis (VL) endemic area. After providing the proof-of-concept, the diagnostic accuracy was estimated on blood from 247 non-endemic control persons and on blood and bone marrow from 173 confirmed VL, 39 probable VL and 87 non-VL patients from south-eastern Nepal. The PCR showed a specificity of 99.64% [95% confidence interval (CI): 98.93-100%) on non-endemic controls and a sensitivity of 92.1% (95% CI: 87.6-96.6%) on blood and 92.9% (95% CI: 89-96.8%) on bone marrow from the confirmed VL patients. Leishmania DNA was detected in blood and bone marrow of 67.6% (95% CI: 50.8-80.9%) and 71.8% (95% CI: 56.2-83.5%) of the probable VL patients, respectively, and of 38.2% (95% CI: 28-49.4%) and 29.9% (95% CI: 21.3-40.2%) of the non-VL patients, respectively. The PCR showed 97% concordance with a positive DAT status while for a negative DAT status this was only 41.3% (kappa-index 0.416, 95% CI: 0.30-0.53). Our findings indicate that PCR alone rather provides a marker for infection than a marker for disease and its role in VL diagnosis in endemic regions is discussed.