Monitoring the size of the leprosy problem: which epidemiological indicators should we use?

The purpose of the study was to discuss the interpretation of epidemiological trends in leprosy, using currently available indicators. A number of leprosy-endemic countries and regions were chosen for which epidemiological data have been published for a period of at least 15 years. Using these examples, relative merit of the registered prevalence rate, the case detection rate, the children proportion among new cases and proportion of new cases with grade 2 disability will examined for interpreting the leprosy situation in these countries. Considerable drop of the registered prevalence rates (PR) were evident in all endemic countries. However, this decline was due largely to shortening of treatment and 'cleaning' of leprosy registers and has not been reflected in the annual case detection rates (CDR), except in a few countries. The proportion of new cases with grade 2 impairment had decreased substantially, which indicates earlier case finding. However, the proportion of children among new cases did not change much in the past decade. It is indicate that transmission is still continuing. We reiterate the conclusion of the ILA Technical Forum that the (annual) case detection rate is the most appropriate indicator for monitoring of leprosy situation in a given country or area. Two additional indicators that helped to interpret the CDR were the proportion of new cases with grade 2 impairments, reflecting the delay between occurrence and diagnosis of the disease, and the proportion of children among new cases, which is used as a proxy indicator for recent transmission.