Failure to detect a prozoning anti-Fy^a in the serum of a chronically transfused patient

A 78-year-old white male presented to our facility with vascular occlusion. He was Group A, D-positive, with a negative indirect antiglobulin test (antibody screen). Records at our facility, 4 years prior to this admission, indicated a history of anti-Fy^a, and Fy(a−) units were provided. A referring hospital had transfused the patient for “chronic anemia” (1-3 units weekly for 2 years), and he had received eight units (untested for Fy^a) immediately prior to his transfer to our facility for acute hemorrhage. Only the presence of anti-IH in the serum was documented. To detect possible immune red cell destruction, the patient was monitored by our facility at 24-hour intervals with a direct antiglobulin test and antibody screen. On day 4, a 4+ anti-Fy^a was identified in the serum and the DAT was negative. Three days later anti-K was also identified. The serologic picture remained unchanged for 10 days, when the DAT became positive. Concurrently, a mixed-field Fy^a typing (on the patient’s chloroquinediphosphate-treated cells) was detected. Repeat Fy^a typing of all units transfused at our facility confirmed their Fy(a-) status. From the day of admission, eluates on every sample, using a low pH technique, showed anti-Fy^a specificity. Titration of the anti-Fy^a but not in neat serum. Although a prozoning phenomenon is uncommon, thi in the sample drawn on admission reacted from a dilution of 4 through 2,048 s case study suggests that a prozoning anti-Fy^a present in the patient’s serum may have been a contributing factor to his “chronic anemia.” Intmunobenurtology 1992;8:44–46.