RESUMO
There is a need for a simple, sensitive, and specific test for the serodiagnosis of leprosy. A passive hemagglutination (PHA) test for leprosy was developed to meet these requirements. A synthetic disaccharide, conjugated to bovine serum albumin and specific for the phenolic glycolipid of Mycobacterium leprae, was sensitized to aldehyde preserved and tanned sheep erythrocytes (SRBC). The sensitized SRBC were used for testing sera from leprosy and tuberculosis cases and normal controls at 1: 64 and 1:128 serum dilutions. It was found that if the hemagglutination reaction at greater than or equal to 1: 128 is considered positive, the test was positive in 84.2% of 38 cases of multibacillary leprosy, 16.7% of 24 cases of paucibacillary leprosy, 16.7% of 6 contacts of multibacillary leprosy, 11.8% of 51 cases of tuberculosis, and 3.7% of 54 blood donors. If the cutoff value used was 1:64, the test was more sensitive but less specific. The results are similar to that of an ELISA for IgM antibody to the same synthetic antigen. The present PHA test is simple and sensitive, but moderately specific. Its simplicity and sensitivity make it highly suitable for large-scale screening of contacts in leprosy-endemic areas.