A prospective study to validate various clinical criteria used in classification of leprosy: a study from a tertiary care center in India.

Background: Various clinical criteria are used to categorize leprosy patients into paucibacillary (PB) and multibacillary (MB), thus aiding in appropriate treatment. However, comprehensive studies validating these criteria are minimal.

Aims: To assess sensitivity and specificity of different clinical criteria individually and in combination for classifying leprosy into PB/MB spectrum.

Method: A prospective study was conducted wherein 50 newly diagnosed, untreated leprosy cases were recruited and classified into PB and MB using the following clinical criteria: number of skin lesions (NSL), number of body areas affected (NBAA), and size of largest skin lesion (SLSL). Patients with pure neuritic leprosy, diffuse macular type of lepromatous leprosy, and with reactions were excluded. Sensitivity and specificity of these clinical criteria in classification was calculated taking histopathological findings as gold standard.

Results: Among 50 patients, 37 were males and 13 were females with a mean age of 32.08 ± 16.55 years. The sensitivity and specificity of NSL, NBAA, and SLSL was 94.74 and 87.1%, 94.74 and 61.29%, and 73.68 and 16.13%, respectively. Combining all three criteria, the sensitivity increased to 100%, but specificity decreased drastically to 12.9%. The ROC curve for NSL, NBAA, and SLSL showed a cutoff of ≥6 skin lesions, ≥3 body areas affected, and ≤2 cm lesion to classify as MB.

Conclusion: The current WHO system of leprosy classification based on NSL seems to be best among available clinical criteria. Uniform and sensible application of this criteria itself assures appropriate categorizing and leprosy treatment with reasonable sensitivity and specificity.