The IMPACT Score: Does Sex Matter?

Abstract

ObjectiveThe Index for Mortality Prediction After Cardiac Transplantation (IMPACT) score is a quantitative risk index that predicts 1-yr mortality risk, derived from United Network for Organ Sharing (UNOS) data in which women are underrepresented. The validity of the IMPACT score in 1-yr mortality risk after OHT in women is unknown. The objective of this study is to assess differences in score performance by sex. We hypothesize that the IMPACT score is a poor predictor of 1-yr mortality risk after OHT in women. DesignExternal validation study including patients 18 years and older first-time single organ OHT recipients from The International Society of Heart and Lung Transplantation (ISHLT) data from 2009-2018. Demographic and clinical characteristics were compared by sex. IMPACT score was calculated and regression models constructed for the entire sample, and stratified by sex. Model discrimination was assessed with the area under the receiver operating characteristic curve (AUROC) and calibration was assessed graphically. SettingN/A InterventionsN/A ParticipantsPatients 18 years and older first time single OHT recipients from ISHLT registry from 2009-2018. Measurements and Main ResultsFor 1-yr mortality, the AUROC (95% CI) for the full sample was 0.59 (0.57-0.60); 0.58 (0.55-0.61) for women; 0.59 (0.58-0.61) for men. 1-yr mortality was 9.4% in the overall cohort, with no difference in mortality by sex (9.0% vs 9.6% women vs men, p=0.22). ConclusionsThe IMPACT score exhibited poor discrimination and calibration in the ISHLT 2009-2019 cohort, overall and by sex. There was no difference in 1-yr mortality between women and men.