Two Latex Tests for Australia Antigen in Subjects with and without Hepatitis

Abstract

With latex particles coated with guinea pig or rabbit antibodies to Australia (Au) antigen, one third of Au-positive acute hepatitis sera gave weak agglutination patterns similar to the nonspecific reaction of 10% of normal sera. More than 10% were negative and the rest caused strong agglutination. After Au antigen had ceased to be detectable by complement fixation (CF) in 23 patients, 9 to 16 still were positive with the latex tests. This is due to rheumatoid factor (RF) or a similar factor appearing during hepatitis, since (a) the latex test was 32-fold less sensitive than CF for the specific detection of Au antigen; (b) 10 out of 10 latex-positive CF-negative hepatitis sera were positive in the RF test; and (c) 20 out of 20 Au-CF-negative sera from rheumatoid arthritis patients without hepatitis were positive in the latex-Au test. In the present form, latex tests are unacceptable for use on patients’ sera due to lack of specificity and sensitivity. Qualified use on the healthy population seems acceptable, but only under certain conditions. Parallel results, with quantitative rather than qualitative differences, were obtained with 2 latex tests of different sources and composition.