Efficacy of fluorescent microscopy versus modified Fite-Faraco stain in skin biopsy specimens of leprosy cases - a comparative study.

BACKGROUND: Histopathological examination of skin remains the cornerstone in the diagnosis of leprosy. At a few centers, fluorescent microscopy has been found to be useful in detecting more acid-fast bacilli (AFB) compared to modified Fite-Faraco staining but is sparsely documented. Hence, we studied the sensitivity of fluorescent microscopy and modified Fite-Faraco stain in the detection of Mycobacterium leprae in tissue sections.

METHODS: Patients attending our outpatient department during January 2019 to June 2020 with the clinical features of leprosy were examined, and the diagnosis was confirmed by histopathology after informed consent. Tissue sections were stained by fluorescent stain and modified Fite-Faraco stain. Bacillary index was calculated for each case.

RESULTS: Forty patients were recruited after following the inclusion and exclusion criteria. AFB were demonstrated in 20 patients by modified Fite-Faraco stain and in 27 patients with fluorescent stain. The sensitivity of fluorescent staining method (67.5%) was higher than modified Fite-Faraco stain (50%). Bacillary index was increased in 26 out of 40 cases by the fluorescent staining compared to the modified Fite-Faraco staining. Chi-square value was 69.3 and P value was 0.000, indicating a statistically significant correlation.

LIMITATIONS: Fluorescent microscope is expensive, and trained people are needed to identify the bacilli.

CONCLUSION: Fluorescent staining is more sensitive than modified Fite-Faraco staining in the detection of AFB in tissue sections. The bacilli detected per field were high with the fluorescent staining compared to the modified Fite-Faraco method.