A new principle for the detection of specific IgM antibodies applied in an ELISA for hepatitis a

A new test principle for the detection of specific IgM‐class antibodies was developed and applied in an Enzyme‐Linked Immuno Sorbent Assay (ELISA) for the detection of hepatitis A IgM antibodies. A solid phase coated with anti IgM was incubated successively with serum sample, specific antigen, and enzymelabeled F (ab') 2 fragments from IgG antibodies against the antigen and enzyme substrate. F(ab') 2 fragments were used to avoid interference with rheumatoid factor. Specificity and sensitivity are very high. This test principle appears generally applicable in the diagnosis of infectious and parasitic diseases by testing only one serum sample.