Diagnostic problems of early leprosy in field studies.

A Series of exercises were undertaken in order to develop methodology for consistency and reliability of clinical diagnosis of leprosy under field conditions in longitudinal studies. It was observed in initial studies that the field investigators could miss about 35% of cases of leprosy, mostly those with early manifestations. After training and experience, the proportion of missed cases came down to about 20%. In about 14% of females with patches suggestive of leprosy the patches were present in the covered areas of the body and so are likely to be missed during examination in field situations. One hundred forty two individuals with suspicious and definite leprosy lesions detected by paramedical workers were examined by a senior medical officer experienced in leprosy on two different occasions at an interval of three months for leprosy diagnosis. The concordance rates for diagnosis and classification of leprosy were about 80% and 70% respectively; and corresponding values for kappa were 0.59 and 0.62 similar to earlier experiences in inter-observer variation studies.