Interpretation of AlloMap® in Clinically Stable Combined Heart-Kidney Transplant Recipients

Abstract

PurposeAs the number of patients undergoing heart-kidney transplantation (HKT) increases, new strategies for dual organ surveillance emerge. AlloMap® gene expression profiling is a widely adopted non-invasive tool utilized to monitor immune quiescence after heart transplant (HT) with the recommended threshold to rule out cellular rejection being 34. The interpretation of AlloMap® in combined HKT surveillance is not well defined. We aimed to determine the utility of AlloMap® for heart surveillance in stable HKT recipients.MethodsAlloMap® data collected from two transplant centers were reviewed retrospectively. Clinically stable patients with HKT (study group) and HT (control group) were included in the study. The HKT and HT cohorts were matched for age, ethnicity, sex, renal and cardiac function, and CMV serologic status. Serial AlloMap® distributions versus time were analyzed by two-sample Kolmogorov-Smirnov (K-S) analysis.ResultsThe study included 25 HKT recipients and 25 HT recipient matched controls transplanted between 1993 and 2020. Over the observed follow-up period (55 days to 18.4 years), there was no difference in AlloMap® scores between groups. In the time interval from 6 months to 24 months, the median AlloMap® scores were higher for HKT vs HT, 33.00 [95% CI, 29.87-34.08] vs 30.00 [95% CI, 28.99-30.92], p=0.028. The 1-year survival in both cohorts was 100% with no cardiac graft dysfunction or biopsy proven rejection (≥2R).ConclusionAlloMap® scores were slightly higher in HKT vs HT recipients between 6 months and 24 months post-transplant. As the HKT AlloMap® scores are near the threshold for possible acute cellular rejection, further investigation is warranted to define interpretation of AlloMap® in combined HKT surveillance. As the number of patients undergoing heart-kidney transplantation (HKT) increases, new strategies for dual organ surveillance emerge. AlloMap® gene expression profiling is a widely adopted non-invasive tool utilized to monitor immune quiescence after heart transplant (HT) with the recommended threshold to rule out cellular rejection being 34. The interpretation of AlloMap® in combined HKT surveillance is not well defined. We aimed to determine the utility of AlloMap® for heart surveillance in stable HKT recipients. AlloMap® data collected from two transplant centers were reviewed retrospectively. Clinically stable patients with HKT (study group) and HT (control group) were included in the study. The HKT and HT cohorts were matched for age, ethnicity, sex, renal and cardiac function, and CMV serologic status. Serial AlloMap® distributions versus time were analyzed by two-sample Kolmogorov-Smirnov (K-S) analysis. The study included 25 HKT recipients and 25 HT recipient matched controls transplanted between 1993 and 2020. Over the observed follow-up period (55 days to 18.4 years), there was no difference in AlloMap® scores between groups. In the time interval from 6 months to 24 months, the median AlloMap® scores were higher for HKT vs HT, 33.00 [95% CI, 29.87-34.08] vs 30.00 [95% CI, 28.99-30.92], p=0.028. The 1-year survival in both cohorts was 100% with no cardiac graft dysfunction or biopsy proven rejection (≥2R). AlloMap® scores were slightly higher in HKT vs HT recipients between 6 months and 24 months post-transplant. As the HKT AlloMap® scores are near the threshold for possible acute cellular rejection, further investigation is warranted to define interpretation of AlloMap® in combined HKT surveillance.