Detection of anti-HLA antibody by flow cytometry in patients with a left ventricular assist device is associated with early rejection following hearttransplantation

Background Patients with a left ventricular assist device (LVAD) as a bridg e to heart transplantation (HT) often have elevated levels of panel reactiv e antibodies (PRA). The clinical significance of anti-human histocompatibil ity leukocyte antigen (HLA) antibodies detected by flow cytometry in PRA ne gative patients remains unclear. Methods. Eighteen patients who underwent LVAD placement as a successful bri dge to PIT had standard anti-human globulin complement-dependent cytotoxici ty and retrospective flow cytometry assays performed to detect class I anti -HLA antibodies. A positive flow result was defined as a fluorescent ratio of greater than or equal to 3:1 versus a negative control. Results. Six patients had anti-HLA antibodies detected by flow cytometry, U nivariate analysis demonstrated more moderate-severe rejection episodes (IS HLT greater than or equal to IIIA) at 2 months (0.83+/-0.75 vs. 0; P=0.04) and a trend toward decreased time to first rejection (61+/-17 vs. 225+/-62 days; P=0.06) in these patients. No differences were observed in donor-reci pient HLA mismatch or 1 year Kaplan-Meier survival between patients with or without anti-HLA antibodies. Conclusion. Despite a negative PRA, LVAD patients with class I anti-HLA ant ibodies detected by flow cytometry have a greater incidence of moderate-sev ere rejection in the first 2 months after HT. Flow cytometry may be a usefu l clinical tool in screening PRA negative LVAD patients before transplantat ion. Patients with positive anti-HLA antibody screening by flow cytometry m ay require more intensive immunosuppression in the early post-MT period.