Rapid method for diagnosis of leprosy by measurements of antibodies to the M. leprae 35-kDa protein: comparison with PGL-I antibodies detected by ELISA and "dipstick" methods.

A new rapid immuno-chromatographic test card for the detection of antibodies to the Mycobacterium leprae 35-kD protein is described. The new assay is compared in the same group of subjects with a direct enzyme ELISA method for 35-kD antibodies and with assays for anti-phenolic glycolipid-I (PGL-I) antibodies using a standard ELISA as well as the recently described "dipstick" method. Good concordance was found between the rapid methods and the corresponding ELISA methods. The detection of untreated paucibacillary leprosy by the 35-kD test card was 59% compared with 27% for the PGL-I dipstick; however, the specificity for the 35-kD test card was 90% compared with 100% for the PGL-I dipstick in an endemic population. The potential application of these new, rapid serologic methods for the diagnosis of leprosy under field conditions is discussed.