To determine a cold agglutinin titer

To determine a cold agglutinin titer

• A. 37°C separation and 4°C testing.
• B. 4°C separation and 4°C testing.
• C. 4°C separation and 37°C testing.
• D. 37°C separation and 37°C testing.

Answer: (A)

Cold agglutinins are IgM antibodies that only cause RBC clumping at low temperatures, so the test must reveal agglutination specifically at cold temps. Separating the components at 37°C prevents in vitro cold-induced clumping during handling, which could falsely alter the titer. The actual titration is then performed with incubations at 4°C, where these antibodies actively bind and agglutinate the red cells. By doing serial dilutions and observing at 4°C, the highest dilution that still shows agglutination gives the titer. If separation were done at 4°C, artifactual clumping could occur during handling, and if testing were done at 37°C, there would be little to no agglutination to measure.

Cold agglutinins are IgM antibodies that only cause RBC clumping at low temperatures, so the test must reveal agglutination specifically at cold temps. Separating the components at 37°C prevents in vitro cold-induced clumping during handling, which could falsely alter the titer. The actual titration is then performed with incubations at 4°C, where these antibodies actively bind and agglutinate the red cells. By doing serial dilutions and observing at 4°C, the highest dilution that still shows agglutination gives the titer. If separation were done at 4°C, artifactual clumping could occur during handling, and if testing were done at 37°C, there would be little to no agglutination to measure.