Sensitivity of a Rapid Mix Test with Combined Synthetic Antigens Derived from Mycobacterium Leprae PGL-1 for Diagnosis and Surveillance of Leprosy

Introduction: In the Americas, Brazil contributes 91.63% of the total cases and the state of Pará still has high endemia for leprosy. Objective: To analyze the performance of a rapid test for the diagnosis and epidemiological surveillance of leprosy in endemic areas. Methods: The sample consisted of 70 MB multibacillary leprosy (MB) patients, 63 paucibacillary (PB) patients, and 80 intradomiciliary consanguineous contacts (ICSCO) of patients. A rapid test with a 15-minute reading was applied using two prototypes: prototype 1, double test with trisaccharide antigen (NT-P-BSA) at 1a. line (83.2 ng/test) and disaccharide antigen (ND-O-BSA) at 2a. (83.2 ng/test), both with a flow of 0.08 μL/mm with a 10 μC membrane, anti-IgM conjugate with a flow of 0.040 μL/mm and a Tris-Triton and prototype 2 runner buffer with MIX antigen (trisaccharide + disaccharide) in the same concentrations and conditions of prototype 1. Results: The comparison of the MIX test positivity rate and the disaccharide or trisaccharide doublet test across all samples was statistically significant, demonstrating that the MIX test had higher seropositivity rates compared to the ND-O-BSA or NT-P-BSA. It was demonstrated that the MIX test showed a good performance, with 25.39% of the PB patients negative for the disaccharide and trisaccharide duplet test, but positive for MIX. Conclusions: These data suggest the potential for further optimizing the performance by adding other synthetic antigens to the MIX antigens.