Diagnostic Utility of Multiplex Polymerase Chain Reaction in Patients of Clinically Suspected Pure Neuritic Leprosy by Identifying Mycobacterium leprae in Skin Biopsy Samples and Nasal Swabs.

Pure neuritic leprosy (PNL) often remains underdiagnosed due to the lack of simple, reliable diagnostic tools to detect Mycobacterium leprae. This study aimed to investigate the utility of multiplex polymerase chain reaction (MPCR) in easily accessible and less invasive biopsy sites, including skin biopsy samples and nasal swabs (NSs), to detect M. leprae. A total of 30 (N = 30) clinically suspected and untreated patients with PNL were recruited. Nasal swabs and skin biopsy samples from the innervation territory of an "enlarged nerve" were collected. DNA was extracted and subjected to MPCR (targeting leprae-specific repetitive element [RLEP], 16S rRNA, and SodA genes) and RLEP-PCR (individual gene PCR). The PCR products were analyzed by 3% agarose gel electrophoresis. In 30 patients with clinically suspected PNL, 60% (N = 18) of skin biopsy samples and 53% (N = 16) of NSs were found positive for M. leprae DNA by MPCR, whereas only 23.3% (N = 7) of skin biopsy samples and 10% (N = 3) of NSs were found positive by RLEP-PCR. MPCR demonstrated a greater positivity rate than did RLEP-PCR for detection of M. leprae. Serologic positivity for anti-natural disaccharide-octyl conjugated with bovine serum albumin (ND-O-BSA) antibodies was 80% (16/20), including 35% (7/20) of PNL patients for which the skin MPCR was negative. Both serologic positivity and skin MPCR positivity were observed in 65% of patients (N = 20). Multiplex polymerase chain reaction is a useful tool for detection for M. leprae in skin biopsy samples and NSs in clinically suspected cases of PNL, with the added advantages of being less invasive and technically easier than nerve biopsy.