A retrospective study of positive 37 degrees C indirect antiglobulin test (IAT) for compatibility following negative antibody screens in a hospital laboratory revealed an unexpectedly high incidence of Wra-incompatible units. Over the course of 1 month 1112 routine patients' samples containing no other atypical antibodies were tested for the presence of anti-Wra. Anti-Wra was found in 88 patients, an incidence of 7.9%. Testing of 5098 healthy blood donor samples found 54 donors positive for anti-Wra, an incidence of 1.06%. A survey of 5253 healthy blood donor samples for Wra antigen found only two Wra-positive samples, suggesting an incidence between 1 in 1000 and < 1 in 10,000. The significance of this finding is discussed in relation to the continuing use of an IAT compatibility test.

Atypical antibody detection in DiaMed microtubes using a low-ionic-strength saline (LISS) indirect antiglobulin technique (IAT) was assessed using both serum and plasma. During the first period of the study all atypical antibodies originally detected in serum were also detected in EDTA plasma with comparable reaction strengths. Two of 73 antibodies were not detected in citrated plasma. During the second period of the study all routine antibody screens were performed in both serum and EDTA plasma. More clinically significant antibodies were detected in EDTA plasma than in serum. More false positives and non-specific antibodies were also detected in EDTA plasma. It is concluded that EDTA plasma is a suitable medium for antibody detection using LISS IAT in DiaMed gel microtubes.