Comparative Evaluation of RLEP-PCR and Conventional Laboratory Methods for Confirmation of Clinically Diagnosed Early-stage Leprosy in Eastern India

Abstract

Introduction: Leprosy is an infectious disease caused by Mycobacterium leprae (M. leprae). Diagnosis of leprosy is confirmed based on cardinal signs and symptoms along with supportive laboratory investigations. Early diagnosis and treatment of new cases are essential to prevent disease burden and spread in community. Aim: To evaluate the efficacy of currently available laboratory tests like M.leprae-specific repetitive element Polymerase Chain Reaction (RLEP-PCR) and conventional methods like, Slit Skin Smears (SSS), Histopathology (HP) and Fite-Faraco (FF) staining for detection of M. leprae in clinically diagnosed cases of early- stage leprosy. Materials and Methods: A cross-sectional study of 82 newly diagnosed cases of leprosy was carried out in S.C.B Medical College, a tertiary care hospital of Odisha, India from September 2018 to August 2020. For every case, skin tissue was punched out to get biopsy for HP and FF staining and incised for SSS. At least two SSS slides were prepared per case. One SSS slide was stained by modified Ziehl-Neelsen (ZN) staining to demonstrate Acid Fast Bacilli (AFB). The other SSS slide was air dried and the dried material was scraped off to perform PCR. Data were analysed by Statistics software IBM Statistical Package for the Social Sciences (SPSS), version 24.0. Association between categorical variables was studied by using Chi-square test. Comparison of mean±SD and median (IQR) were done by using independent sample‘t’ test. Agreement on different types of laboratory methods was done by using Kappa test. Results: Among 82 cases, 68.3% were RLEP-PCR positive, 56% had relevant chronic granulomatous features histopathologically, 39% were FF stain positive, and only 29% were ZN stain positive. Improvement in case detection of 39%, 29.3%, and 12.2% by PCR over SSS, FF Stain and HP respectively proved superiority of PCR over other procedures. Conclusion: PCR was most sensitive to detect leprosy both in pauci and multibacillary groups, thus considered as investigation of choice for diagnosis of early-stage leprosy.

Keywords

• fite faracco staining
• histopathology
• leprae-specific repetitive element-polymerase chain reaction
• slit skin smear