Evaluation of Polymerase Chain Reaction (PCR) with Slit Skin Smear Examination (SSS) to Confirm Clinical Diagnosis of Leprosy in Eastern Nepal

<div><p>Background</p><p>Detection of <i>Mycobacterium leprae</i> in slit skin smear (SSS) is a gold standard technique for the leprosy diagnosis. Over recent years, molecular diagnosis by using PCR has been increasingly used as an alternative for its diagnosis due to its higher sensitivity. This study was carried out for comparative evaluation of PCR and SSS microscopy in a cohort of new leprosy cases diagnosed in B. P. Koirala Institute of health Sciences, Dharan, Nepal.</p><p>Methodology/Principal Findings</p><p>In this prospective crossectional study, 50 new clinically diagnosed cases of leprosy were included. DNA was extracted from SSS and PCR was carried out to amplify 129 bp sequence of <i>M</i>. <i>leprae</i> repetitive element. Sensitivity of SSS and PCR was 18% and 72% respectively. Improvement of 54% case detection by PCR clearly showed its advantage over SSS. Furthermore, PCR could confirm the leprosy diagnosis in 66% of AFB negative cases indicating its superiority over SSS. In the paucibacillary (PB) patients, whose BI was zero; sensitivity of PCR was 44%, whereas it was 78% in the multibacillary patients.</p><p>Conclusions/Significance</p><p>Our study showed PCR to be more sensitive than SSS microscopy in diagnosing leprosy. Moreover, it explored the characteristic feature of PCR which detected higher level of early stage(PB) cases tested negative by SSS. Being an expensive technique, PCR may not be feasible in all the cases, however, it would be useful in diagnosis of early cases of leprosy as opposed to SSS.</p></div

Flow chart of overview of methods.

<p>Flow chart of overview of methods.</p

ROC curve of PCR diagnosis with RJ classification.

<p>ROC curve of PCR diagnosis with RJ classification.</p

Sensitivity of Microscopy and PCR with Confidence interval (CI).

<p>Sensitivity of Microscopy and PCR with Confidence interval (CI).</p

Flow diagram of participants.

<p>Flow diagram of participants.</p

Agarose gel image of the <i>M</i>. <i>leprae</i> PCR products.

<p>M; Molecular markers. Lanes 1–5; Patient samples. L6; Negative control. L7; Positive control.</p

Correlation of WHO clinical types, results of skin smears for AFB and PCR.

<p>Correlation of WHO clinical types, results of skin smears for AFB and PCR.</p

Risk factors for PKDL development in past treated VL patients, exact logistic regression.

α<p>OR : odds ratio;</p>β<p>CI: confidence interval;</p>δ<p>IQR: Inter quartile range;</p>σ<p>SSG : Sodium stibogluconate.</p>*<p>Median unbiased estimates (MUE).</p

Recruitment and outcome of PKDL screening survey.

<p>Flow chart of study population: from number of patients screened to number of PKDL cases identified.</p

Risk of PKDL in three VL-treatment groups, Kaplan-Meier survival analysis.

<p>Kaplan-Meier survival analysis for three types of VL treatment.</p