OR52 AT1R antibody in pediatric heart transplant patients: What are we really detecting

Abstract

Aim The frequency and impact of AT1R antibodies in pediatric heart transplantation has not been well studied. Our aim was to measure AT1R antibodies (AT1R-Ab) in this patient population and pediatric controls and to assess for non-specific reactivity in this assay. Methods We included 42 patients ( n = 154 samples) for whom pre- and post-transplant sera and HLA Ab data were available. AT1R-Ab were measured by ELISA (One Lambda Inc.). Samples were tested/interpreted as per product insert. Age-matched, sex-balanced, non-transplant patient controls ( n = 27) were collected from cardiac–catheterization laboratory. A subset with positive results ( n = 52 sera from 20 patients) was re-tested following Adsorb Out (One Lambda Inc.). Analysis was performed using GraphPad. Results No significant difference was observed between patient and control AT1R antibody levels (Fig. 1). Values over 40 U/ml were detected in 38% of patient sera. Adsorbed sera had significantly decreased AT1R values vs non-adsorbed sera (Fig. 2A). There was no significant change in AT1R-Ab from pre- to post-transplant overall in either group but a higher proportion of patients changed from positive to negative using adsorbed vs non-adsorbed sera (20% vs 12.5%) (Fig. 2B and C). Conclusions A high proportion of patients and controls were positive for AT1R-Ab, however, many sera appear to be false positive, possibly due to BSA reactivity or incomplete blocking in the assay. As more assays for non-HLA Ab are added into our clinical algorithms, appropriate controls must be included. A ‘blank’ well would be useful in this assay for accurate interpretation of results. Association of the adsorbed and non-adsorbed AT1R-Ab to transplant outcomes is currently being assessed.