@article{757535ef70044c50b3bc869a8893101c,
title = "The heart transplant allocation change attenuates but does not eliminate blood group O waitlist outcome disadvantage",
abstract = "Background: Patients with blood group O have historically been disadvantaged in the United Network for Organ Sharing (UNOS) heart transplant allocation system. We sought to determine whether the new UNOS allocation system implemented in 2018 had an impact on waitlist and post-transplant outcomes among blood groups. Methods: Using the UNOS database we included all adult patients listed and transplanted with first-time single-organ heart transplant between 10/17/15 and 10/1/21. For post-transplant outcomes, we separately evaluated all adult patients transplanted with the same time-frame. We used exclusion criteria and censoring to limit biases from changing clinical practices around the allocation change (10/18/2018), and from unequal or inadequate follow-up. We compared clinical characteristics and outcomes before and after the allocation change among each blood group. Fine-Gray and Cox regression models were used to estimate the effect of the new allocation system on competing waitlist outcomes- transplantation, death-or-removal from waitlist- and post-transplant survival, respectively. Results: Of the 21,565 patients listed for transplantation 14,000 met criteria for waitlist analysis (7,035 in the old system vs. 6,965 in the new), and 7,657 met criteria for post-transplant analysis (3,519 in the old system vs. 4,138 in the new). Among each blood group, new allocation change was associated with higher transplantation rates lower waitlist days and lower waitlist mortality (except Group AB). However, despite improvements, Group O was still associated with worse waitlist outcomes for each metric compared to non-O Groups. The new allocation system did not have a significant impact on post-transplant survival among any blood groups. Conclusion: Changes in heart transplant allocation have attenuated but not eliminated blood group O disadvantage in access to donor hearts.",
keywords = "UNOS allocation policy, blood group O, heart transplant",
author = "Patel, {Jay N.} and Dmitry Abramov and Marat Fudim and Okwuosa, {Ike S.} and Rabkin, {David G.} and Chung, {Joshua S.}",
note = "Funding Information: We conducted an analysis of competing waitlist outcomes to test the claim that the new UNOS allocation system improved waitlist times and transplantation rates for patients listed for heart transplantation, both overall and among various blood groups. We also conducted a separate analysis to measure the impact of the new allocation system on post-transplant survival among various blood groups. We obtained UNOS registry data from the Organ Procurement and Transplantation Network on October 1st, 2021. This work was supported in part by Health Resources and Services Administration contract 234-2005-37011C. The content is the responsibility of the authors alone and does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products or organizations imply endorsement by the U.S. Government. We conducted an analysis of competing waitlist outcomes to test the claim that the new UNOS allocation system improved waitlist times and transplantation rates for patients listed for heart transplantation, both overall and among various blood groups. We also conducted a separate analysis to measure the impact of the new allocation system on post-transplant survival among various blood groups. We obtained UNOS registry data from the Organ Procurement and Transplantation Network on October 1st, 2021. This work was supported in part by Health Resources and Services Administration contract 234-2005-37011C. The content is the responsibility of the authors alone and does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products or organizations imply endorsement by the U.S. Government. We included all adult patients listed and transplanted with first-time, single-organ heart transplant between 10/18/15 and 10/1/21. To avoid biases from changing clinical practices and unequal or inadequate follow-up, we: 1) excluded patients from the old system listed in the year prior to allocation change; 2) censored patients from the old system with more than 1 year follow-up (this was done because as a historical comparator, patients from the old UNOS cohort have significantly longer follow-up than those in the new UNOS cohort. Waitlist and post-transplant follow-up were therefore censored at one year to avoid bias from unequal follow-up between the two groups), and 3) excluded patients from the new system with less than 1 year follow-up. In addition, for post-transplant outcomes, we excluded patients listed in the old system and transplanted in the new (Figure 1). We stratified patients according to blood group: A, B, AB and O. Our study design was submitted to the institutional review board (IRB) at the Loma Linda University Medical Center. The IRB determined that the study did not meet the definition of human subject research because it did not involve identifiable information, no data or specimens were collected, and there was no direct intervention or interaction. Thus, review or approval was waived by the IRB. This work was in strict compliance with the International Society for Heart and Lung Transplantation ethics statement. For each listed patient, we obtained characteristics at the time of transplant listing registration. Demographic characteristics included age, gender, body-mass index (BMI), ethnicity, listing region and education level. Comorbidities included diabetes, dialysis, cerebrovascular accident, prior malignancy, cigarette smoking, prior cardiac surgery and implantable cardiac defibrillator. Additional covariates indicating disease severity included renal function (most recent creatinine), right heart catheterization hemodynamics, use of inotropes, mechanical circulatory support and ventilator support. For each transplanted patient we obtained characteristics at the time of listing (as above), time of transplantation and characteristics from the donor. Recipient characteristics at the time of transplantation included age, BMI and additional covariates indicating disease severity: ICU status, use of inotropes and mechanical circulatory support, ventilatory support, renal function (most recent creatinine), total bilirubin and right heart catheterization hemodynamics. Donor characteristics included age, gender, recipient-donor mismatch, BMI, blood group, cause of death, diabetes, cocaine use, renal function (most recent creatinine), total bilirubin, left ventricular ejection fraction, ischemic time and distance (miles) from the transplant center. We followed listed patients to one of three competing waitlist outcomes—transplantation, waitlist death or waitlist removal; patients remaining on the waitlist after one year were censored. We followed transplanted patients to determine freedom from death or re-transplantation; patients with follow-up longer than one year were censored. Patients coded as {\textquoteleft}lost to follow-up{\textquoteright} were also censored. There was < 10% missingness for all variables and outcomes included in the analyses (supplemental Tables 6a and 6b). Missing data were imputed to the mean for continuous variables, and to zero for categorical variables (for dichotomous variables, imputation to 0 implies {\textquoteleft}not present{\textquoteright}. For multi-response variables, imputation to 0 implies {\textquoteleft}other{\textquoteright}). Characteristics at listing, transplantation and from the donor were compared before and after the UNOS allocation change, both overall and among blood groups (Tables 1, 3 and 4; Supplemental Tables 1, 3 and 4). A two-sample t test was used to compare continuous variables and chi-square test for categorical variables. Fine-Gray proportional sub-hazard models were used to estimate the effect of allocation change on competing waitlist outcomes—transplantation, death, or removal from waitlist—both overall and among each blood group. Unadjusted and adjusted sub-hazard ratios (SHR) were reported for each competing outcome; multivariable regression models were adjusted for characteristics at listing as outlined above (Tables 2; Supplemental Table 2). A Fine-Gray sub-hazard ratio < 1 or > 1 is interpreted as the covariate (new UNOS allocation system) having an effect on the cumulative incidence function or probability of events occurring over time.5 Cox proportional sub-hazard models were used to estimate the effect of allocation change on post-transplant survival- freedom from death or re-transplantation- both overall and among each blood group. Unadjusted and adjusted hazard ratios (HR) were reported; multivariable regression models were adjusted for characteristics at listing, transplantation and from donor as outlined above (Table 5; Supplemental Table 5). A Cox hazard ratio < 1 or > 1 is interpreted as the covariate (new UNOS allocation system) having an effect on the survival function. All analyses were performed using Stata version 17.0 (StataCorp, College Station, Texas 77845 USA). All statistical tests were two-sided and p < 0.05 was considered significant. Funding Information: This work was supported in part by Health Resources and Services Administration contract 234‐2005‐37011C Publisher Copyright: {\textcopyright} 2022 The Authors. Clinical Transplantation published by John Wiley & Sons Ltd.",
year = "2022",
month = may,
doi = "10.1111/ctr.14620",
language = "English (US)",
volume = "36",
journal = "Clinical Transplantation",
issn = "0902-0063",
publisher = "Wiley-Blackwell",
number = "5",
}