High incidence of IgG antibodies to phenolic glycolipid in non-leprosy patients in India.

Purified phenolic glycolipid (PGL-1) from Mycobacterium leprae was used to detect IgG antibodies against PGL-1 in leprosy patients in an enzyme-linked immunosorbent assay (ELISA). A total of 698 sera were screened; they came from patients suffering from leprosy, autoimmune disease, myeloma, tuberculosis and sexually transmitted diseases (STDs). Cases with miscellaneous diseases and persons undergoing AIDS screening were also included. Sera from lepromatous and tuberculoid leprosy patients gave positivity rates of 60.5% and 41.7%, respectively. In non-leprosy cases, the PGL-1 ELISA showed an overall positivity rate of 6.9%; this was greatest in patients with tuberculosis (43.8%) followed by autoimmune diseases (40.9%) and miscellaneous cases including liver diseases (37.9%). This study emphasizes that PGL-1 ELISA has a low predictive value for diagnosis of active infection by Mycobacterium leprae. Positive reactions in a significant percentage of patients with autoimmune disease are intriguing and need indepth study.