RLEP PCR as a Definitive Diagnostic Test for Leprosy from Skin Smear Samples in Childhood and Adolescent Leprosy

The present study was conducted to evaluate the results of RLEP M leprae PCR using slit skin scraping samples (SSS) & compare the results with routine slit skin smears for AFB. Seventy three cases of both sexes (42 males and 31 females), 4 to 18 years of age (up to 5 years 4; 6-10 years 17; and the rest 52 between 11 to 18 years), clinically diagnosed cases of leprosy with hypopigmented / erythematous lesions associated with partial/total loss of sensation and/or presence of thickened nerves, diagnosed and classified by the criteria of IAL (1982), were included after obtaining their informed written consent. Skin smears from 30 non-leprosy cases of pulmonary tuberculosis, meningitis, skin diseases etc were also tested for M leprae RLEP PCR following the same protocol, after their informed consent and were included as controls. After clinical examination & clinical categorization two skin smears were taken, one for Z-N staining for AFB & another for M leprae RLEP PCR. After DNA extraction & amplification, electrophoresis was done on 2% agarose gel. Presence of 129bp fragment amplicon (RLEP of M leprae) was considered as positive result for the presence of M leprae DNA. Acid fast bacilli (AFB) positivity in smears after ZN staining was observed in 17/73 (cases (23.3%) and RLEP PCR positivity in 56/76 cases (76.71%). All controls showed negative results with M leprae RLEP PCR. The RLEP PCR technique had a significantly greater positivity ie more than three times that of AFB positivity on ZN staining (p< 0.001). The test can be easily performed and is a less invasive technique than biopsy for establishing the definitive diagnosis of leprosy.