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PITFALLS AND AMBIGUITIES IN ANTIBODY SCREENING IN PATIENTS WITH CARDIAC ASSIST DEVICES: THE ROLE OF FLOW PRA BEADS.
C. Schall 1, L. Klingman 2, D. Cook 2 and R. Valdez 1. 1 Pathology, University of Michigan Health System, Ann Arbor, MI and 2 Allogen Laboratories, Cleveland, OH .
Accurate identification of anti-HLA antibody (Ab) in patients with cardiac assist devices can be problematic because of a high incidence of non-specific serum reactivity. This phenomenon may be due to plastic components within certain devices. In our experience, ELISA tests are most frequently affected by this aberrant reactivity, posing a significant pitfall in assessing and reporting the extent of sensitization in these patients.
Thirteen adult heart transplant candidates with implanted cardiac assist devices were tested for HLA Class I/II Ab by ELISA. All patients received multiple transfusions when the device was placed and none had received a prior transplant. In all cases, Ab screening by ELISA consistently revealed high PRA values or ambiguous results in serial samples, with either specific HLA Ab or multispecific patterns observed. Subsequent testing using flow cytometry single antigen beads (FC) failed to confirm the high PRA values. Moreover, non-specific reactivity was seen in 8 patients with only possible HLA specificities reported for the other 5. The specificities assigned by ELISA were dissimilar to those detected by FC. Results obtained by FC were reported. Eight patients were successfully transplanted with negative crossmatches.
ELISA assays frequently give falsely high PRA values and false positive HLA Ab specificities in patients with implanted intravascular devices. Using ELISA alone, therefore, may result in a significantly lower opportunity for these patients to be transplanted. Identification of an aberrant ELISA result pattern should prompt one to perform FC testing, as this is a more reliable methodology for accurately identifying HLA antibodies in this subset of patients.