Weakening or loss of antibody reactivity after prewarm technique.

BACKGROUND: The prewarm (PW) technique is a popular approach to determine whether cold antibodies are reacting at 37 degrees C or to detect potentially clinically significant antibodies in the presence of cold autoantibodies. The PW technique has been criticized because of unexpected loss of antibody reactivity and inappropriate use of the method.

STUDY DESIGN AND METHODS: Sera containing 94 antibodies were tested by routine and PW PBS-, LISS-, and PEG-IAT. LISS-IAT was also compared to PW PBS-IAT. Sera were also tested to determine the role of low-affinity antibodies in loss of reactivity by PW methods.

RESULTS: PW PBS-IAT and PW LISS-IAT showed that 40 and 47 percent of antibodies were weakened, respectively, compared to LISS-IAT; reactivity for 14 percent of antibodies was completely lost by each PW method. By PW PBS-IAT, 34 percent of antibodies were weakened compared to PBS-IAT. PW PEG-IAT showed weakened reactivity by 56 percent of antibodies compared to PEG-IAT; reactivity of seven out of seven PEG-dependent antibodies was completely lost. Of 67 antibodies, 19 percent were defined as low affinity. Of 64 samples tested by the PW method and for low-affinity antibodies, only 6 of 30 that showed decreased reactivity by the PW method appeared to be due to low-affinity antibodies; only 6 of 12 samples that appeared to contain low-affinity antibodies also showed decreased reactivity by the PW method.

CONCLUSION: Antibody reactivity of potentially clinically significant antibodies can be decreased or missed by PW methods. Antibody enhancement media does not ensure antibody detection by PW methods.