The value of IgM antibodies to PGL-I in the diagnosis of leprosy.

An ELISA has been used to measure IgM antibodies to phenolic glycolipid-I (PGL-I) in previously undiagnosed patients who were suspected of leprosy on purely clinical grounds. The certainty of clinical diagnosis was classified as either "firm" or "indefinite." Leprosy was confirmed in 133 of 161 patients on the basis of positive slit-skin smears and/or skin and/or nerve histopathology. All 58 patients with multibacillary leprosy (BB, BL, or LL) were correctly diagnosed clinically, as were 50 of 54 patients (93%) with a firm diagnosis of BT or TT leprosy. The firm clinical diagnoses were more accurate than either the slit-skin smear or ELISA data. However, there were 44 patients (27% of total), designated "rule out leprosy" (RO), for whom the clinical diagnosis was indefinite. The clinical suspicion of leprosy (RO) was correct in only 24 (55%) of these patients who had BT leprosy. The slit-skin smears were positive in only 20% of these patients compared to 50% for the ELISA. It was concluded that the PGL-I IgM ELISA may have its greatest diagnostic confirmatory value in paucibacillary disease because paucibacillary leprosy comprises the major source of clinical diagnostic difficulty.