HLA Sensitization in Pediatric Pre-transplant Cardiac Patients Supported by Mechanical Assist Devices: the Utility of Luminex

Abstract

HLA sensitization rates in children on extracorporeal membrane oxygenation (ECMO) or ventricular assist devices (VADs) are unknown. In addition, panel-reactive antibody (PRA) assessment is increasingly being performed by Luminex, whose role in comparison to other conventional methods is unclear. We investigated HLA sensitization of mechanically supported children using established PRA methods and then retested stored serum using Luminex to assess its impact on initial PRA results and post-heart transplant (post-HTx) outcomes. Data on 22 pre-HTx ECMO or VAD patients (0 to 18 years of age) included: age; duration of mechanical support; use of homograft; red cell transfusion volume; PRAs; and outcome. Comparative data were collected from 10 non-supported, age-matched controls. Median age of the 13 ECMO and 9 VAD patients was 1.4 and 192 months (p < 0.001), respectively. Six (27%) device patients and 4 (40%) controls had baseline PRAs >10% (p = 0.7). No ECMO but 6 VAD patients were sensitized after 50 +/- 51 days of support (p = 0.02). Compared with ECMO, VAD patients had higher Class I PRAs according to enzyme-linked immunoassay (p = 0.03). VAD patients had higher final vs initial PRAs for Class I (p = 0.05) and II (p = 0.04) antigens. HLA sensitization was independent of transfusion volume. Only complement-dependent cytotoxicity (CDC) Class I PRAs were different from their respective Luminex values (p = 0.03). Four HTx patients with initially low PRAs but elevated post hoc Luminex assays had no rejection at 3.8 +/- 1.6 years post-HTx. Infants supported with ECMO are at low risk for HLA sensitization. Because it provides full antibody specificity disclosure, Luminex complements more conventional PRA assays by quantitatively identifying potential donor-specific antibodies, which should facilitate the virtual crossmatch process, thereby minimizing post-HTx humoral rejection risk.