Diagnosis of type A hepatitis by fecal IgA antibody against hepatitis A antigen.

A method was developed for the early diagnosis of type A hepatitis. The method involved the detection of fecal antibody against hepatitis A antigen (HAAg). We followed 6 patients who contracted type A hepatitis in an outbreak for the fecal excretion of HAAg and antibody against HAAg (anti-HA) by immune electron microscopy. Fecal anti-HA appeared soon after the disappearance of HAAg, at around the zenith of serum transaminase, and persisted approximately 4 mo after the development of hepatitis. Fecal anti-HA was of IgA class, since it was completely absorbed by an anti-IgA column, but not affected by anti-IgG or anti IgM column. Owing to its early appearance and short duration, fecal anti-HA allows an early diagnosis of type A hepatitis by the test of a single specimen. Fecal anti-HA would be assumed to herald the termination of the period during which patients should be segregated from the community to prevent secondary infection.