Pediatric Heart Donor Assessment Tool (PH-DAT): A novel donor risk scoring system to predict 1-year mortality in pediatric heart transplantation

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Background

In this study we sought to quantify hazards associated with various donor factors into a cumulative risk scoring system (the Pediatric Heart Donor Assessment Tool, or PH-DAT) to predict 1-year mortality after pediatric heart transplantation (PHT).

Methods

PHT data with complete donor information (5,732) were randomly divided into a derivation cohort and a validation cohort (3:1). From the derivation cohort, donor-specific variables associated with 1-year mortality (exploratory p-value < 0.2) were incorporated into a multivariate logistic regression model. Scores were assigned to independent predictors (p < 0.05) based on relative odds ratios (ORs).

Results

The final model had an acceptable predictive value (c-statistic = 0.62). The significant 5 variables (ischemic time, stroke as the cause of death, donor-to-recipient height ratio, donor left ventricular ejection fraction, glomerular filtration rate) were used for the scoring system. The validation cohort demonstrated a strong correlation between the observed and expected rates of 1-year mortality (r = 0.87). The risk of 1-year mortality increases by 11% (OR 1.11 [1.08 to 1.14]; p < 0.001) in the derivation cohort and 9% (OR 1.09 [1.04 to 1.14]; p = 0.001) in the validation cohort with an increase of 1-point in score. Mortality risk increased 5 times from the lowest to the highest donor score in this cohort. Based on this model, a donor score range of 10 to 28 predicted 1-year recipient mortality of 11% to 31%.

Conclusion

This novel pediatric-specific, donor risk scoring system appears capable of predicting post-transplant mortality. Although the PH-DAT may benefit organ allocation and assessment of recipient risk while controlling for donor risk, prospective validation of this model is warranted.

Section snippets

Methods

The UNOS database STAR file was used for this study. The STAR file contains transplant data on all transplants in the USA from October 1987 onward. UNOS is a private, non-profit organization that oversees the Organ Procurement and Transplant Network (OPTN) of the United States and operates in agreement with federal policy. The institutional review board waived full review of this project due to the de-identified nature of the UNOS data set.

Results

A total of 5,732 patients were included in the analysis. Seventy-five percent (4,316) of them were randomized to the derivation cohort and the remainder (1,416) were included in the validation cohort. For all patients, median age was 5 (range 0 to 13) years, 55% (3,156) were male and 59% (3,356) were white. The most common diagnosis was cardiomyopathy, at 49% (2,795). The median estimated eGFR was 83.3 (range 61.5 to 107.8) ml/min/1.73 m2, and 18% (1,036) were on ventilator support before

Discussion

This pediatric-specific donor risk scoring system (the PH-DAT) is a unique tool developed based on 5 donor factors (ischemic time, cerebrovascular accident as the cause of death, donor–recipient height ratio, LVEF, eGFR) that predicted 1-year mortality from a large multi-institutional data set. In addition, this risk score is associated with graft failure out to 5 years post-transplant. Patients transplanted with a donor risk score of ≥16 had a significantly lower 5-year graft survival of 67%

Limitations

This study has both strengths and limitations. We were able to study a nationally representative sample of pediatric heart transplant recipients in the contemporary era. The relatively large sample size allowed for examination of characteristics that are not widely available and thus have been rarely used, if ever, in the analysis of the UNOS database. We only analyzed donor organs that were accepted, and thus further work is needed to determine whether this system has a role in assessing

Disclosure statement

The authors have no conflicts of interest to diclose. We thank Dr. Erin Haynes for her contribution to the manuscript in her role as the chair of the thesis committee for the primary author (F.Z.). This study was presented as a podium presentation at the 36th annual meeting and scientific sessions of the International Society for Heart and Lung Transplantation, April 2016, Washington, DC.

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