Comparison of Synthetic Antigens for Detecting Antibodies to Phenolic Glycolipid I in Patients with Leprosy and Their Household Contacts

Abstract

Three synthetic antigens related to the natural antigen phenolic glycolipid I (PGL-I) were compared for their efficacy in detecting leprosy when used as antigens in an enzyme-linked immunosorbent assay (ELISA) for IgM antibody to PGL-I. Absorbance values for ELISAs using the three antigens correlated well (.79<r<.99) and had a high rate of agreement (89.5%<a<98.4%). Of three subjects (household contacts of patients with leprosy) who later developed the disease, one with lepromatous and one with indeterminate leprosy were seropositive by ELISAs using the three antigens before the clinical onset of disease; one who developed borderline tuberculoid leprosy was seronegative. The predictive value of a positive result for the test was very low (99.9%) because of the low prevalence of leprosy in French Polynesia (1.78 per 1000). The high sensitivity, specificity, and efficiency of the tests using the three antigens confirmed their great value for serodiagnosis of leprosy, especially the multi bacillary form; the ELISA using NTP seems to be more specific and sensitive for detecting the paucibacillary form.