Can anti-PGL-1 and anti-NDO-LID-1 antibody titers be used to predict the risk of reactions in leprosy patients?

Leprosy patients may present reactional episodes classified as type I or reversal reaction and type II or erythema nodosum leprosum. Early diagnosis of these reactions is hampered by lack of diagnostic tests. This study aimed at evaluating anti-Mycobacterium leprae antibody levels in reactional and nonreactional leprosy patients at the time of diagnosis. Clinical data and serum samples of 224 patients diagnosed between 2009 and 2010 were collected in the municipality of Rondonópolis-MTBR. Quantification of anti-phenolic glycolipid-1 (PGL-1) IgM antibodies of M. leprae was obtained by the enzyme-linked immunosorbent assay method and anti-natural octyl disacharide-leprosy IDRI diagnostic (NDO-LID-1) IgM/IgG semiquantitative rapid test. We obtained low serological levels of anti-PGL-1 and anti-NDO-LID-1 for tuberculoid (T) (1.56% and 15.62%) and borderline tuberculoid (BT) patients (7.95% and 26.13%), medium levels in the borderline-borderline (BB) (47.91% and 68.75%), and high levels in lepromatous (LL) (93.33% and 100%) and borderline-lepromatous (BL) (88.0% and 100%). When comparing the reactional groups (RI and RII) with without reaction (WR) group at the time of diagnosis, we observed a statistically significant difference between the groups; patients with RII presented higher serological response: 66.66% anti-PGL-1 and 91.66% anti-NDO-LID-1. In respect to patients who developed a reaction after the initial diagnosis, they also showed significant positivity for both anti-PGL-1 and anti-NDO-LID-1 in comparison to the patients who stayed without reaction in the study period (P<0.0001). These results allow us to conclude that serological tests may contribute to an early diagnosis of RII and that the anti-NDO-LID-1 test was demonstrated to be a better indicator.