ROC curve analysis of NGF: according to the ROC curve (Figure 1), the optimal cut-off value of serum NGF concentrations as an indicator for early disability in leprosy was 81.43 ng/L, with a sensitivity of 100% and a specificity of 100% [AUC 0.719; 95% CI (0.719-0.918); p < 0.05] (Table 2). This evidence concerns the gene NGF and leprosy.