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

Abstract

BackgroundDetection of Mycobacterium leprae 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.Methodology/Principal FindingsIn 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 M. leprae 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.Conclusions/SignificanceOur 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.

Polymerase Chain Reaction (PCR) as a Potential Point of Care Laboratory Test for Leprosy Diagnosis—A Systematic Review

“…De Wit et al (1993) reported on the utility of PCR for detection of M. leprae in nasal swab specimens amplifying the 531-bp pra gene, demonstrating 79.6% positivity of PCR [22]. Kyeong-Han Yoon reported PCR on slit skin samples, which was subsequently reported by many others [23,24,25,26,27,28]. PCR on biopsies has been reported by Wichitwechkarn et al (1995), with a mean PCR positivity of 66% and subsequently by many others.…”

“…Conventional PCR targeting a single gene has been found to be the most frequently reported method. Several authors have used conventional PCR on slit skin, biopsy, urine, blood [27,37,38,39,40]. On the other hand, few studies have utilized multiplex PCR on slit skin and biopsies, amplifying more than one target sequence, at the same level of laboratory settings as conventional PCR [21,26,35,41].…”

Polymerase Chain Reaction [PCR] versus Slit Skin Smear in Diagnosis of Leprosy

“…Eventually if untreated, leprosy leads to disability and disfigurement. Thus, early detection of M. leprae is important to timely identification and treatment of patients [2] .…”

Reação em cadeia da polimerase em amostras de linfa coletadas em papel filtro no diagnóstico da hanseníase

“…For exemple, Kang et al [9] extracted DNA from the scalpel blade used for collecting bacilloscopy and found 73% positivity with RLEP primers -67.7% of samples with negative bacilloscopy presented positive PCR. Siwakoti et al [10] extracted DNA from microscope slides used for bacilloscopy, with 44% sensitivity of the PCR in PB patients.…”