Heterophilic antibody interference in a tryptase immunoassay.

Objective: Investigation of the susceptibility of a tryptase immunoassay to interference by heterophilic antibodies.

Methods: The effect of preincubation with a blocking agent was investigated on the levels of tryptase, human anti-mouse antibodies and IgM rheumatoid factor in sera with elevated IgM rheumatoid factor levels.

Results: In 5 of 30 sera with IgM rheumatoid factor, tryptase levels were reduced at least twofold after pre-incubation with blocking reagent.