How do heterophile antibodies interfere with immunoassays, and what strategies can reduce this interference?

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Heterophile antibodies interfere by bridging the antibodies used in a sandwich immunoassay. In a typical setup, the capture antibody is bound to a solid phase and the detection antibody binds the analyte to form a sandwich. A heterophile antibody in the patient serum can bind both the capture and detection antibodies at once, creating a bridge even when the target analyte is absent, which produces a signal that looks like a true positive (and can sometimes cause false negatives if the interference masks the real signal). This kind of interference can affect many immunoassays, not just those for hormones, and is a common source of misleading results.

To reduce this interference, one approach is to use blocking reagents that neutralize heterophile antibodies or pre-treat the sample to remove or mask them. Another effective strategy is to alter the assay design or reagents—for example, use antibodies from different species, employ Fab or F(ab’)2 fragments that lack the Fc region, or switch to a different assay format less susceptible to bridging. In practice, laboratories may also confirm suspicious results with an orthogonal method or a different platform to ensure accuracy.