Rapid serodiagnosis for leprosy--a preliminary study on latex agglutination test

In this study, we have developed two latex agglutination tests (LATs) with phenolic glycolipid-I (PGL-I) and natural disaccharide-octyl-bovine serum albumin (ND-O-BSA) as antigens in 110 leprosy patients (LL = 30, BL = 30, BT = 30, and TT = 20), 50 tuberculosis cases, and 30 normal controls. These two LATs were compared with corresponding ELISAs (ND-O-BSA ELISA and PGL-I ELISA) and analyzed by the chi-squared test. There were no significant differences between the two LATs (PGL-I LAT and ND-O-BSA LAT) and their corresponding ELISAs. There was an increase in the proportion of positive cases detectable which coincided with the clinical classification of leprosy, i.e., lepromatous cases were more likely to be positive than tuberculoid cases. LATs are more simple and rapid than ELISAs and have high sensitivity (77% in ND-O-BSA LAT, 80.5% in PGL-I LAT) and specificity (99% in both LATs). LATs may become useful tools for the immunodiagnosis of leprosy in the field. The stability and repeatability of LATs are discussed in detail.