Seroepidemiological studies in subsided cases of multi and paucibacillary types of leprosy using FLA-ABS test

FLA-ABS test was carried out in 145 subsided cases of multibacillary (BL/LL) and 197 subsided cases of paucibacillary (TT/BT/I) types. The period of subsidence varied from 0-5 years or more. It was observed that percentage positivity decreases with the subsidence of the disease. In multibacillary cases, FLA-ABS positivity was 95% (active cases), 50% (after 1 year of subsidence) and 36% (after 5 years of subsidence) whereas in paucibacillary types FLA-ABS positivity was 80% (active cases), 34% (after 1 year of subsidence) and 19% (after 5 years of subsidence). A significant proportion of multibacillary subsided cases continued to be positive at high titres (1:160 and 1:640) even after 5 years of clinical subsidence. This implies the presence of continuous antigenic stimulus resulting in high antibody titres even after several years of clinical subsidence. On the other hand percentage positivity at high titres gradually decreased with the increased duration in paucibacillary cases.