Which factor can cause a false-negative ABO typing result?

Which factor can cause a false-negative ABO typing result?

• A. Incubation at 37°C
• B. Rouleaux
• C. Positive DAT
• D. LISS

Answer: (A)

The key idea here is how temperature affects antibody–antigen interaction in ABO typing. The antibodies used to detect A and B on red cells are mainly IgM and they agglutinate best at cooler or room temperatures. If you incubate the test at body temperature (37°C), these IgM antibodies bind less effectively, so the cells may not clump even when the corresponding antigen is present. That lack of visible agglutination produces a false-negative ABO result. Other factors can interfere in different ways. Rouleaux can mimic clumping and often lead to misinterpretation that looks like a positive reaction rather than a true negative. A positive DAT indicates antibodies or complement on the patient’s red cells and can complicate interpretation, sometimes masking or altering reactions. LISS is used to enhance agglutination and decrease the chance of a false negative, so it wouldn’t explain a true false-negative result in this scenario.

The key idea here is how temperature affects antibody–antigen interaction in ABO typing. The antibodies used to detect A and B on red cells are mainly IgM and they agglutinate best at cooler or room temperatures. If you incubate the test at body temperature (37°C), these IgM antibodies bind less effectively, so the cells may not clump even when the corresponding antigen is present. That lack of visible agglutination produces a false-negative ABO result.

Other factors can interfere in different ways. Rouleaux can mimic clumping and often lead to misinterpretation that looks like a positive reaction rather than a true negative. A positive DAT indicates antibodies or complement on the patient’s red cells and can complicate interpretation, sometimes masking or altering reactions. LISS is used to enhance agglutination and decrease the chance of a false negative, so it wouldn’t explain a true false-negative result in this scenario.