Anti-phenolic glycolipid-I seropositivity among household contacts of leprosy patients in Egypt

Leprosy is a chronic, debilitating disease lacking a definitive diagnostic biomarker. Serum anti-phenolic glycolipid-I (PGL-I) IgM antibody level is considered an important diagnostic and prognostic marker for leprosy patients. However, there is limited evidence on the role of anti-PGL-I IgM antibody level as early predictive biomarker of subclinical infection among Egyptian household contacts of leprosy patients. This study investigates the relationship between specific leprosy risk factors, diagnostic parameters of eighty-three leprosy cases, and serum anti-PGL-I IgM antibody levels in their corresponding household contacts. Our results demonstrate that anti-PGL-I IgM antibody level was significantly higher among contacts when more than four residents shared the same room with a leprosy case (p = 0.032). Additionally, anti-PGL-I IgM antibody level markedly increased in contacts of leprosy cases with disabilities (p = 0.001) or damaged nerves (p = 0.001). Our ROC curve analysis of anti-PGL-I antibody level as a predictor of exposure or infection among contacts revealed a cut-off value of 0.1, with a sensitivity of 75.0% and a specificity of 54.5%, indicating that most exposed household contacts are correctly identified. The overall accuracy of the ROC curve analysis was 72.3%, highlighting the practical utility of anti-PGL-I antibody level as a predictor for exposure or infection among household leprosy contacts. In conclusion, seropositivity of anti-PGL-I antibodies (> 0.1) among household leprosy contacts may be associated with a higher leprosy exposure risk. Continuous monitoring of anti-PGL-I antibody level in household leprosy contacts may potentially contribute to early detection and management of leprosy.