Clinicopathological Diagnosis of Leprosy: Comparative Evaluation of Three Staining Methods for Acid Fast bacilli in Slit Skin Smears and Biopsy Specimens

Detection of acid fast bacilli (AFB) in slit smears and histopathological specimens is of paramount importance for diagnosis and classification of leprosy. In this study the results of conventional staining technique for AFB has been compared with modified rapid AFB and Fite Faraco stain in slit skin smears and punch biopsy specimens from clinically diagnosed cases of leprosy. Processed skin biopsies and slit skin smears of 42 patients attending outdoor clinic of a tertiary care centre were stained with three stains viz Fite Faraco, modified Rapid AFB and conventional Ziehl Neelsen staining. According to clinical diagnosis the maximum number of patients belonged to Borderline Tuberculoid leprosy which correlated with histopathological diagnosis of skin biopsy. Clinical and histopathological correlation was not observed in 14/42 cases - histopathological categorization of biopsies from these cases revealed Indeterminate leprosy (9 cases), Tuberculoid Leprosy (2 cases), Borderline Lepromatous (1 case), Histoid Leprosy (1 case) and Mid- Borderline Leprosy (1 case). Maximum positivity for AFB was seen with Fite Faraco staining followed by modified Rapid AFB both in the biopsy specimens and slit skin smears. Fite Faraco staining showed highest sensitivity in both paucibacillary and multibacillary cases followed by modified rapid AFB and conventional AFB staining. Though biopsy and slit skin smears have their individual diagnostic advantages and limitations, biopsy deserves to be viewed as gold standard in case of difficulty in arriving at a confirmed diagnosis. Findings of this study need to be validated in a larger number of leprosy cases at community level studies and correlated with classification currently recommended by WHO and NLEP.