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Diagnosing leprosy: revisiting the role of the slit‐skin smear with critical analysis of the applicability of polymerase chain reaction in diagnosis
Author(s) -
Banerjee Surajita,
Biswas Nibir,
Kanti Das Nilay,
Sil Amrita,
Ghosh Pramit,
Hasanoor Raja Abu Hena,
Dasgupta Sarbani,
Kanti Datta Pijush,
Bhattacharya Basudev
Publication year - 2011
Publication title -
international journal of dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 93
eISSN - 1365-4632
pISSN - 0011-9059
DOI - 10.1111/j.1365-4632.2011.04994.x
Subject(s) - medicine , polymerase chain reaction , leprosy , sss* , mycobacterium leprae , biopsy , lepromatous leprosy , multiplex polymerase chain reaction , pathology , multiplex , context (archaeology) , biology , gene , bioinformatics , genetics , paleontology
Background Diagnosing leprosy is challenging, especially in early‐stage cases, and the need for a sensitive diagnostic tool is urgent. Polymerase chain reaction (PCR) holds promise as a simple and sensitive diagnostic tool, but its usefulness in the Indian context requires further evaluation. Slit‐skin smear (SSS) remains the conventional method of leprosy detection. Hence, this study was undertaken to evaluate and compare the diagnostic efficacy of PCR versus that of SSS. Methods Punch biopsy of skin and SSS were obtained from the active margins of lesions. Cases were clinically grouped according to whether they were multibacillary (MB) or paucibacillary (PB) and classified into tuberculoid (TT), borderline tuberculoid (BT), borderline lepromatous (BL), lepromatous (LL), histoid, and indeterminate groups after clinicopathological correlation. DNA was extracted from biopsy specimens, and multiplex PCR was carried out incorporating primers intended for the amplification of a specific 372‐bp fragment of a repetitive sequence of Mycobacterium leprae DNA. Results Among 164 patients, PCR was positive in 82.3%. The sensitivity of PCR was significantly greater ( P < 0.0001) than that of SSS in both the MB (85.9% vs. 59.8%) and PB (75.4% vs. 1.8%) subgroups; the difference in sensitivity in the PB subgroup is remarkable. Positivity by PCR and SSS was found in 100% of LL and histoid leprosy, but PCR had significantly greater ( P < 0.0001) positivity in BT leprosy and was of definite increased value in indeterminate and TT leprosy. Conclusions Polymerase chain reaction had higher sensitivity compared with SSS, especially in diagnostically challenging and PB cases. Thus, the use of this costly but sensitive tool should be restricted to this subgroup, because SSS is sufficiently sensitive in the diagnosis of LL and histoid leprosy.