Slit-skin smear for the classification of leprosy; are we wasting time and resource?

Introduction: Leprosy is a chronic neglected tropical disease, classified into two groups: multibacillary (MB) and paucibacillary (PB) leprosy based on the number of skin lesions and nerve involvement. A positive skin slit smear (SSS) result automatically puts a patient in the MB category. Although guidelines do not recommend routine use of SSS for classification and diagnosis of leprosy, it is performed for most patients in Ethiopia. However, the added value of performing SSS for the classification of leprosy on top of clinical classification is unclear.

Methodology: A cross sectional study was done using routine laboratory and clinical data from September 2018 to January 2020 at Boru Meda General Hospital, Ethiopia. All newly diagnosed leprosy cases were included. Descriptive statistics were performed to calculate frequencies and proportions.

Results: We included 183 new leprosy patients in our study, of which 166/183 (90.7%) were MB patients and 17/183 (9.3%) were PB patients. All clinical PB cases and 150/166 (90.4%) clinical MB patients had SSS done. All PB patients had negative SSS result and 68 (45.3%) clinical MB patients had a positive result. Based on the SSS, no patient with a clinical classification of PB was reclassified to MB.

Conclusions: SSS microscopy was performed routinely for all leprosy cases without changing the classification and management of patients in Boru Meda Hospital. Therefore, we recommend restricted and rational use of the SSS for PB cases in which SSS could change management.