Can the interval between antibody identifications be increased for alloimmunized patients?

Clinical consequences of a 30-day interval between antibody identifications

BACKGROUND

While studies have shown that antibody detection may be delayed if an antibody identification (ABID) is not performed every 3 days, little data exist on the potential major risk of an acute hemolytic transfusion reaction (aHTR).

STUDY DESIGN AND METHODS

At our institution, if no change in the screen, or a positive crossmatch, ABIDs are performed every 30 days. Between January 1, 2015 and May 31, 2019, all new antibodies detected within 28 days of a prior transfusion were identified. Testing results and patient charts were reviewed for evidence of hemolysis. The $211 patient charge was used to determine the cost for ABIDs performed during the studied time period.

RESULTS

For 36 patients, a new clinically significant alloantibody was detected within 28 days of an antigen-positive transfusion. Only one of these patients had a history of prior alloimmunization and put at possible risk due to the ABID policy. For this patient, while there was less than the expected increment to an antigen-positive unit, there was no clinical or laboratory evidence of an aHTR. During this same time, 6095 ABIDs were performed, at a cost of approximately $1.29 million, and 72,665 red cell transfusions occurred.

CONCLUSION

With an ABID every 30 days, only one patient, over 4.5 years, was put at potential risk for hemolysis from one transfusion (0.001% of the total units transfused during the time period). While antibody detection may be delayed, performing ABIDs every 30 days saves money and medical laboratory scientist time and should be balanced against potential patient harm.

The Prevalence of unexpected antibodies in Saudi's plasma prior blood transfusion and their association with clinical conditions: A cross-sectional study

Unexpected antibodies, also called irregular antibodies, are not known to exist in a person's serum before testing. This research aims to assess the prevalence of unexpected antibodies and their correlation with several clinical conditions. This cross-sectional prospective study, undertaken from June 2019 to June 2020, included ABO, Rh grouping, cross-matching, and antibody screening. Antibody identification was performed only on patients who tested positive in the screening test. From a total of 9764 participants who were screened for unexpected antibodies, 107 (1.1%) tested positive. The Rh blood group system antibodies were the most frequent, particularly anti-D. There was also a significant correlation between the unexpected antibodies and history of transfusion, pregnancy, and autoimmune diseases as P ≤ 0.05. The most prominent unexpected antibodies in the study belong to the Rh system (Anti-D). Moreover, as a result of the strong correlation between the unexpected antibodies as well as the history of transfusion, pregnancy, and autoimmune diseases, the highest safety criteria must be followed during the transfusion of blood to patients with these clinical conditions.

Reliability of labeling red cell units with minor antigen historical results and process considerations

BACKGROUND

Several approaches are used by blood centers when providing minor (non-ABO/D) antigen-negative RBCs to hospitals. Details vary but include providing results on the unit labeling intended for clinical use without retyping or providing results on packing documents or via computer query requiring confirmation. Recent regulatory changes allow labeling with historical minor antigen results, defined as previously performed by the donor center on two different donations with results linked to the donor and confirmed concordant. Here we investigate causes of discrepancies and identify critical process steps.

STUDY DESIGN AND METHODS

Nine years (2009-2017) of data were reviewed for number, antigen system, and root cause of discrepancies flagged by the computer when retyping donors prior to labeling (internal discrepancies) or reported by the hospital when retested (external discrepancies). Licensed automated (CcEeK) and tube methods were used.

RESULTS

Among 300,000 samples phenotyped for CcEe, K, Fya/b , Jka/b , Ss (>3 million antigens), ∼1,389,960 were repeated on 2nd donation with 397 (1/3501) discordant; 205 Fy, 118 Rh, and 74 others. Of ∼682,691 antigen-negative phenotypes provided on unit labeling, ∼37.5% (256,118) were retyped by hospitals with 29 discrepancies (1/8832), primarily Rh variants.

CONCLUSION

When repeating minor antigen types by serology, discrepancies are primarily associated with weak Fyb , among Caucasian donors, and weak/partial Rh antigens in donors of African ancestry. DNA-based testing avoids these. To label with historical results, accuracy is increased by automated testing with direct computer interface. Testing on two donations with results confirmed to be concordant is not inferior to testing on the current donation.

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

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.