Six kinds of serological tests for leprosy, i.e. fluorescent leprosy antibody absorption
test (FT), enzyme-linked immunosorbent assay (ELISA) using synthetic
disaccharide-BSA antigen (NDH) or synthetic trisacchride-BSA (NTH) or deacylated
(ES) or sonicated (WMT) phenolic glycolipid-1 of M. leprae and passive
hemagglitination test (HAT) using disacchride-BSA antigen, were independently carried
out at several laboratories by using the same set of 413 coded sera which were
composed of 197 sera from the patients with leprosy, 81 from contacts, 84 from the
patients with tuberculosis,27 from the patients with the other skin disease arid 24 from
healthy non-contacts. Serological sensitivity and specificity of these tests were
expressed by the percentage of positive reactions in leprosy and non-leprosy sera,
respectively, The sensitivity of PT and HAT was significantly higher than that of the
other tests in 43 sera from paucibacillary leprosy patients. On the contrary, FT and
NDH showed significantly lower sensitivity than ES and HAT in 154 sera from
multibacillary leprosy patients. Treatment of these patients for 4 years or longer reduced
the sensitivity of every ELISA tests and HAT, which that of FT was elevated by the
treatment for 1 or 3 years. The percentage of positive reactions in FT and HAT were
significantly higher than those in the other tests with the sera from contacts and
non-leprosy cases, suggesting that the former two tests are useful for detecting
subclinical infection with M. leprae although their specificity is lower than ELISA tests.
Concordance between FT and one of the others was very low owing to the difference
in sensitivity and specificity as described above. Every combinations between two
ELISA tests showed good concordance due to a common principle on which the two
tests are based.
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