Evaluation of a new blood test for its potential to indicate leprosy infection prior to the appearance of clinical symptoms.

A test is described that utilized a laser nephelometric measure of the interaction between human serum and a leprosy biopsy suspension to demonstrate household contact with a leprosy index case. None of the test sera was from persons with clinical evidence of the disease. There was a 5:1 ratio of higher level reactors in sera from household contacts vs high level reactors in sera from persons in the surrounding community. This did not appear to be a result of age, sex, family relationship to the index case, or clinical character of the index case. Some index cases had high level serum reactors among their contacts; others did not. This phenomenon was not a function of the clinical classification of the index case. The reason is unknown. This test should provide another practical means to study leprosy.