Evaluation of Slit Skin Smear (SSS) Microscopy for Leprosy in Various Districts of Tamil Nadu

Diagnosis of leprosy is primarily based on clinical criteria. However, quality Slit Skin Smear (SSS) microscopy has a role in correct disease classification and patients' selection for Drug resistance surveillance. This study has been carried out to understand the adequacy of SSS services and its quality among participating laboratories, and to find out the level of concordance and error types among the participating laboratories in comparison with the reference lab. The evaluation of SSS microscopy labs was carried out by performing on-site evaluation (OSE) and panel testing involving 13 laboratories from various centres in five districts of Tamil Nadu. Overall performance was based on scoring the key components – infrastructure, availability of trained manpower, reagents, technique of specimen collection, slide preparation, microscopic examination and reporting of results. Scores more than 70% were considered satisfactory. Among 13 participating laboratories, performance of six (50%) was satisfactory during on-site evaluation; ten had a satisfactory performance in panel testing wherein the participating lab technicians (LTs) read a set of slides prepared, stained and read in advance by the expert LTs of CLTRI. The panel test results revealed a concordance of 55.4% between the participating laboratories and reference laboratories along with an overall error of 30 among 65 smears (46.2%) of which 6 (9.2%) and 24 (36.9%) were major and minor errors respectively. SSS Microscopy services need to be strengthened in terms of infrastructure, logistics and trained manpower.