Validity of FNAC for the Diagnosis of Leprosy

Early and accurate diagnosis of leprosy is crucial because delay may lead to some permanent disability and sequelae. Histopathological examination of skin and nerves and slit skin smears examination to assess the bacillary load, have been the major tools used in the laboratory diagnosis, classification and follow up of patients with leprosy. Histopathological evaluation is not feasible in many leprosy endemic areas. Fine needle aspiration cytology (FNAC) is a simpler tool compared to histopathology for the evaluation of the cytomorphology of skin lesions. Aims of this study are to evaluate the role of cytology in diagnosing leprosy patients, to study the cytomorphology of leprosy lesions in fine needle aspirates and to compare the diagnostic value of FNAC with that of standard histopathological diagnosis. Sensitivity of FNAC in diagnosing leprosy was observed to be BT (87.5%); LL (80%); TT and BL (66.67%) in the descending order. Specificity of FNAC in diagnosing leprosy was in the following order BL (96.29%); followed by LL (96%); TT (92.59%) and BT (85.71%). Positive predictive value was observed to be BT-87.5%; LL-80%; BL-66.67% and TT-50%. Fairly good correlation was observed between clinical, histological and cytomorphological features in the aspirates taken from the skin lesions. A reasonably good sensitivity, specificity, positive and negative predictive values were obtained in all types of leprosy except for mid borderline spectrum. FNAC is a simple, easy, cost effective, relatively non invasive procedure which provides faster results than biopsy. Drawbacks include- “dry taps”, bloody smears and lack of cellular infiltrate in case of macular lesions.