Which phenomenon can cause falsely low results in immunoassays when analyte concentration is very high?

Which phenomenon can cause falsely low results in immunoassays when analyte concentration is very high?

• A. Hook effect
• B. Preanalytical error
• C. Calibration drift
• D. Interference by heterophile antibodies

Answer: (A)

In immunoassays, especially sandwich immunoassays, signals are generated when the analyte creates a bridge between the capture antibody on the solid phase and the labeled detection antibody. When the analyte level becomes extremely high, it can saturate both antibodies independently, preventing the formation of the necessary antibody–analyte–antibody sandwich. Without that sandwich complex, the detector signal drops, so the result appears falsely low despite a very high true concentration. This high-dose hook effect is why diluting the sample and re-measuring can reveal the true, higher level—the dilution allows proper sandwich formation and a higher signal. This phenomenon is specific to the way these immunoassays generate signal; other issues like preanalytical errors, calibration drift, or heterophile antibody interference can cause erroneous results for different reasons and aren’t the defining cause of falsely low results at very high analyte concentrations.

In immunoassays, especially sandwich immunoassays, signals are generated when the analyte creates a bridge between the capture antibody on the solid phase and the labeled detection antibody. When the analyte level becomes extremely high, it can saturate both antibodies independently, preventing the formation of the necessary antibody–analyte–antibody sandwich. Without that sandwich complex, the detector signal drops, so the result appears falsely low despite a very high true concentration. This high-dose hook effect is why diluting the sample and re-measuring can reveal the true, higher level—the dilution allows proper sandwich formation and a higher signal. This phenomenon is specific to the way these immunoassays generate signal; other issues like preanalytical errors, calibration drift, or heterophile antibody interference can cause erroneous results for different reasons and aren’t the defining cause of falsely low results at very high analyte concentrations.