Time interval between antibody investigations among patients who demonstrate serial red cell antibody formation

Abstract

BACKGROUND Current national standards for pretransfusion testing do not address the frequency or optimal time interval to repeat antibody identification testing for patients in whom antibodies have been previously detected. STUDY DESIGN AND METHODS A retrospective review was performed of patients with existing red blood cell (RBC) antibodies who subsequently developed new antibody specificities. Data were drawn from a single institution where the antibody investigation was repeated if the screen suggested a new antibody or if 14 days had elapsed since the previous investigation. Clinically insignificant or drug‐dependent antibodies were excluded. Among cases in which new antibodies were detected within 30 days of a previous sample that already demonstrated existing antibodies, the median and lower 95% confidence intervals for the number of days between the detection of the existing and new antibodies were determined. RESULTS Over a 9‐year period, among 2114 patients with more than 1 antibody, 699 (33%) had serially detected antibodies from separate samples. Among 152 patients whose subsequent antibody was detected within 30 days of the existing antibodies, the median time interval to detection of the new antibody was 13 days. The lower 95% confidence interval was 1 day. By Day 3, 18% of the new antibodies had already appeared. CONCLUSION In patients who form multiple antibodies, the serial emergence of clinically significant antibodies is common. In some patients, detection of a new specificity occurs in a sample drawn shortly after the sample that demonstrated the first antibody. These results have implications for the frequency of pretransfusion testing.

How do we… direct a transfusion service/blood bank with limited laboratory staff

“…A recent study showed it may be possible to extend antibody identification beyond 3 days as long as there is no change in the antibody screen or a positive crossmatch 22 . In cases where patients have warm autoantibodies and are receiving phenotyped RBCs for transfusion, it may also be possible to extend workups beyond 3–14 days or longer; specifics would need to be determined by each individual TS/BB and tailored for their patient population 23 …”

Non-RhD (anti-E) red cell alloimmunization following platelet transfusion: a case report and implications on quality of the platelet concentrates and antibody screening protocols

“…In previously alloimmunized individuals, the rate of additional antibody formation increases by 2–20 fold. 1 As an attempt to reduce the incidence of RCA, many centers have implemented prospective extended antigen matched PRC transfusions for multi-transfused patients to minimize the risk of RCA. However, the patients can still develop alloantibodies despite Rh-K matched PRC transfusions, as seen in our index case.…”

“…The risk of red cell alloimmunization (RCA) is proportional to the number of transfusions. 1 It occurs mainly due to antigen mismatched packed red cell (PRC) transfusions. A minor proportion of cases is attributed to platelets.…”

Clinical consequences of a 30‐day interval between antibody identifications

“…Therefore, practices vary in different laboratories. 7,8 It is possible a new antibody may be masked if it reacts with the same screening cells as the known antibody but would have been identified if an ABID had been repeated more frequently. As a crossmatch is not a full-proof method, the patient may also then be transfused with units positive for the respective antigen for the missed antibody.…”

“…While there are publications addressing the potential frequency of missing antibodies when an ABID is not performed every 3 days, they do not provide details on the clinical consequences of missing antibodies and then transfusing units positive for the respective antigens. 7,8 In this context, we sought to determine if our policy of repeating an ABID every 30 days puts patients at significant risk of aHTRs. To provide information related to potential financial effects, data are also included on the cost of repeat ABIDs.…”