Comparative sensitivity of solid phase versus PEG enhancement assays for detection and identification of RBC antibodies

Blood banks require a sensitive, specific, and efficient method to detect clinically significant RBC antibodies. Solid phase antibody screening methods are popular due to high sensitivity and automation. However, the high degree of reactivity detects “false positive” antibodies of questionable clinical significance leading to additional testing. We studied positive rates of Capture-R vs. PEG methods and categorized RBC antibodies identified by initial test results of 33,564 consecutive samples by Capture-R method. Capture-R was positive in 1084/33,564 (3.2%) of samples. Using PEG as our “gold standard”, PEG confirmed true positivity (i.e., ⩾1 cell reacting) in 710 Capture-R positive samples (65.5%); 374 Capture-R positive samples (34.5%) did not react in PEG (i.e., false positives). Of the 710 samples with true positivity, only 510 showed clinically significant alloantibodies. Using PEG as our “gold standard”, only 2/3 of reactions by Capture-R were considered true positives. Because of ease and automation, Capture-R is popular as a screening test, but a more specific method may be helpful in order to identify truly significant alloantibodies.