The ML flow test as a point of care test for leprosy control programmes: potential effects on classification of leprosy patients.

Objective: To evaluate the use of the ML Flow test as an additional, serological, tool for the classification of new leprosy patients.

Design: In Brazil, Nepal and Nigeria, 2632 leprosy patients were classified by three

Methods: : (1) as multibacillary (MB) or paucibacillary (PB) according to the number of skin lesions (WHO classification), (2) by slit skin smear examination, and (3) by serology using the ML Flow test detecting IgM antibodies to Mycobacterium leprae-specific phenolic glycolipid-I.

Results: The proportion of MB leprosy patients was 39.5, 35.6 and 19.4% in Brazil, Nepal and Nigeria, respectively. The highest seropositivity in patients was observed in Nigeria (62.9%), followed by Brazil (50.8%) and Nepal (35.6%). ML Flow test results and smears were negative in 69.1 and 82.7% of PB patients, while smears were positive in 58.6% of MB patients in Brazil and 28.3% in Nepal. In MB patients, both smears and ML Flow tests were negative in 15.6% in Brazil and 38.3%, in Nepal. Testing all PB patients with the ML Flow test to prevent under-treatment would increase the MB group by 18, 11 and 46.2% for Brazil, Nepal and Nigeria, respectively. Using the ML Flow test as the sole criterion for classification would result in an increase of 11.3 and 43.5% of patients requiring treatment for MB leprosy in Brazil and Nigeria, respectively, and a decrease of 3.7% for Nepal.

Conclusions: The ML Flow test could be used to strengthen classification, reduce the risk of under-treatment and minimize the need for slit skin smears.