Abstract
INTRODUCTION: Leprosy is a chronic disease caused by the bacillus Mycobacterium leprae and remains a public health concern in endemic countries. Early diagnosis is fundamental to prevent transmission and irreversible disabilities. Histopathological identification of acid-fast bacilli in tissue specimens is traditionally considered the laboratory reference standard; however, its sensitivity is limited, particularly in paucibacillary forms. Immunohistochemistry (IHC) has been proposed as an adjunctive diagnostic tool for detecting M. leprae antigens in tissue samples, but its diagnostic accuracy has not been systematically synthesised. This protocol outlines a systematic review aimed at evaluating the sensitivity and specificity of IHC in the laboratory diagnosis of leprosy. METHODS AND ANALYSIS: This systematic review of diagnostic test accuracy studies will include analytical observational studies and clinical trials evaluating IHC in human subjects with suspected leprosy. The reference standard will be defined as the identification of acid-fast bacilli in skin biopsy specimens from patients with compatible clinical presentation using conventional staining methods (eg, Fite-Faraco), with the exclusion of alternative mycobacterial infections when applicable. Searches will be conducted in PubMed/MEDLINE (Medical Literature Analysis and Retrieval System Online), Embase, Scopus, Web of Science and BVS/LILACS (Biblioteca Virtual em Saúde/Latin American and Caribbean Health Sciences Literature), as well as grey literature sources, at 31 May 2026. Two independent reviewers will perform study selection, data extraction using a standardised Microsoft Excel form and risk of bias assessment using the Quality Assessment of Diagnostic Accuracy Studies-2. Sensitivity and specificity estimates will be calculated. If appropriate, a bivariate random-effects meta-analysis will be conducted using RevMan (Review Manager) and Stata. ETHICS AND DISSEMINATION: Ethical approval is not required because this study will use publicly available data. The results will be submitted to a peer-reviewed journal and presented at scientific conferences.