The sensitivity and specificity of fluorescent leprosy antibody absorption (FLA-ABS) test for detecting subclinical infection with Mycobacterium leprae

Abstract

From the examination of 854 sera from different sources by the fluorescent leprosy antibody absorption (FLA-ABS) test, the sensitivity and specificity of this test for leprosy has been confirmed. A positive FLA-ABS test in a non-leprosy individual should be considered as an indicator of subclinical leprosy infection. The subclinical infection rates of two endemic areas ranged from 11.4 to 16.3% and were at least 200 times higher than the cumulative prevalence rate of clinical infection. The combination of a positive FLA-ABS test with a negative Mitsuda reaction indicates that the individual has been infected with Mycobacterium leprae, but cell-mediated immunity has not been induced. Such individuals are at a greater risk of developing multibacillary leprosy and should be carefully followed up or some prophylactic measures should be considered. Since subclinical infection cannot be differentiated from very early leprosy by the FLA-ABS test alone, it is not a reliable diagnostic test of early leprosy.