Comparison of Sensitivity of Radioimmunoassay and Immune Electron Microscopy for Detecting Hepatitis A Antigen in Fecal Extracts

Solid-phase, microtiter ra-dioimmunoassay (RIA) has been compared with immune electron microscopy (IEM) for its sensitivity and usefulness in detecting hepatitis A antigen in clinical fecal specimens. Using relatively crude 5% extracts from stools collected at the Lynchburg Training School and Hospital in 1970 during an epidemic of infectious hepatitis, we have demonstrated the feasibility of RIA as a rapid and reliable screening test. All samples positive for HA Ag by IEM were also positive by RIA. Dilution experiments with HA Ag-positive fecal preparations indicated that RIA is at least as sensitive as IEM. RIA is an appropriate method for reliable, large-scale screening of fecal samples for HA Ag. RIA would appear to be potentially useful in the diagnosis of hepatitis A infection.