Optimal prewarming conditions for Rh antibody testing.

BACKGROUND: Although prewarming (PW) can reduce the confounding agglutination of cold-reactive antibodies when testing for warm-reactive antibodies, PW also can adversely affect the detection of warm-reactive antibodies. This study was conducted to determine PW conditions that optimized Rh antibody detection.

STUDY DESIGN AND METHODS: In 38 plasma samples with Rh system antibodies detected by any of four methods, and in 8 other samples with cold-reactive antibodies, reactivity was assessed by titer and score.

RESULTS: PW to 37 degrees C often reduced reaction scores by all methods especially the low-ionic-strength saline indirect antiglobulin test and bromelin methods. In analyses warming red blood cell (RBC) suspensions or plasma, the reaction scores were decreased only when the RBC suspension was warmed, suggesting that RBC PW decreased Rh antibody reactivity. The warming period ranging from 5 to 30 minutes all decreased Rh system reaction scores, an effect persisting up to 120 minutes. At lower temperatures (27, 30, and 33 degrees C), numbers of samples showing decreased reaction score for Rh system antibodies decreased in a temperature-dependent manner. Testing at 27 degrees C also permitted some agglutination involving cold-reactive antibodies, whereas higher temperatures successfully suppressed their agglutination.

CONCLUSION: PW at 30 degrees C minimizes problems in accurately detecting Rh system antibodies.