Urine-based ELISA using a recombinant chimeric protein for the diagnosis of paucibacillary and multibacillary leprosy

Leprosy diagnosis is difficult to perform due to variable sensitivity and/or specificity of the tests. In addition, the collection of the blood samples requires laboratorial structure and trained professionals. In the present study, the diagnostic efficacy of M1 chimeric protein, which was recently showed to be antigenic for leprosy using a serum-based ELISA, was evaluated against patient urine. Paired serum and urine samples were collected from patients with paucibacillary (PB) and multibacillary (MB) leprosy, tegumentary and visceral leishmaniasis, tuberculosis, Chagas disease, malaria, and HIV-infected subjects. Samples from healthy individuals and household contacts were also used. The protein and peptides used to compose it were used as antigens, and results showed that the four peptides presented good sensitivity and specificity to detect MB leprosy, while M1 protein showed sensitivity and specificity of 98.5 % and 100 %, respectively, to detect both PB and MB leprosy, when an urine-based ELISA was performed. Positive (PPV) and negative (NPV) predictive values were 100 % and 98.3 %, respectively. In a serum-based ELISA, sensitivity and specificity were 96.9 % and 100 %, respectively, with PPV and NPV of 100 % and 96.5 %, respectively. In conclusion, preliminary data suggest that M1 protein could be considered for diagnosis of leprosy by using patient urine.