Introduction:

With the implementation of the new Kidney Allocation System (KAS), deceased donor transplants from blood group A₂ donors can now be implanted into blood group B recipients. However, the safety of this depends on low anti-A₂ titer levels in the recipient. There is a lack of data as to the stability of these titers over time and therefore proper frequency of testing is unknown. This has limited the broad implementation of A₂ to B transplants.

Methods:

From a single center's B waitlist and previous 2-year transplant record, blood group B patients were retrospectively identified who had at least two anti-A₂ titer measurements. Anti-A₂ titer values were collected along with information from the medical record related to possible sensitizing events. In order to account for the inherent imprecision of testing, a significant change in titer levels was defined as > 4-fold difference between measurements.

Results:

The sample included 48 adults (58% male; age 56 + 11 years). Average time between measurements was 13.31 + 6 months. Using the aforementioned criteria 35% (n=17) of patients had significant titer changes. Six patients had a significant decrease in titers, one of which was began immunosuppression and another received a blood transfusion between titers. The remaining 11 patients had a significant increase in titer levels. Between titers 4 underwent systemic antibiotic therapy (a marker of bacteremia) and 2 began hemodialysis, but the remaining 8 had no identifiable sensitizing events. Of the 31 patients with multiple titers that did not change significantly, 2 received a blood transfusion, 1 became pregnant, and 2 were treated with systemic antibiotics between measurements.Conclusion:

Over one third of anti-A₂ titers show significant variability within 1 year of measurement. Careful medical history taking for hypothesized sensitizing events is not adequate to predict significant changes in titer levels. Frequent testing of anti-A₂ titers is required to maintain adequate safety for patients listed for A₂ to B transplants.

CITATION INFORMATION: Radomski S, Rosen-Bronson S, Diedrich B, Langeberg A, Li D, Awwad M, Grafals M, Cooper M, Gilbert A. It's Never too Early to Test: Frequent Anti-A₂ Titer Monitoring in Blood Group B Patients is Necessary. Am J Transplant. 2017;17 (suppl 3).

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