Does Simplicity Compromise Accuracy in ACS Risk Prediction? A Retrospective Analysis of the TIMI and GRACE Risk Scores

Abstract

BackgroundThe Thrombolysis in Myocardial Infarction (TIMI) risk scores for Unstable Angina/Non-ST–elevation myocardial infarction (UA/NSTEMI) and ST-elevation myocardial infarction (STEMI) and the Global Registry of Acute Coronary Events (GRACE) risk scores for in-hospital and 6-month mortality are established tools for assessing risk in Acute Coronary Syndrome (ACS) patients. The objective of our study was to compare the discriminative abilities of the TIMI and GRACE risk scores in a broad-spectrum, unselected ACS population and to assess the relative contributions of model simplicity and model composition to any observed differences between the two scoring systems.Methodology/Principal FindingsACS patients admitted to the University of Michigan between 1999 and 2005 were divided into UA/NSTEMI (n = 2753) and STEMI (n = 698) subpopulations. The predictive abilities of the TIMI and GRACE scores for in-hospital and 6-month mortality were assessed by calibration and discrimination. There were 137 in-hospital deaths (4%), and among the survivors, 234 (7.4%) died by 6 months post-discharge. In the UA/NSTEMI population, the GRACE risk scores demonstrated better discrimination than the TIMI UA/NSTEMI score for in-hospital (C = 0.85, 95% CI: 0.81–0.89, versus 0.54, 95% CI: 0.48–0.60; p<0.01) and 6-month (C = 0.79, 95% CI: 0.76–0.83, versus 0.56, 95% CI: 0.52–0.60; p<0.01) mortality. Among STEMI patients, the GRACE and TIMI STEMI scores demonstrated comparably excellent discrimination for in-hospital (C = 0.84, 95% CI: 0.78–0.90 versus 0.83, 95% CI: 0.78–0.89; p = 0.83) and 6-month (C = 0.72, 95% CI: 0.63–0.81, versus 0.71, 95% CI: 0.64–0.79; p = 0.79) mortality. An analysis of refitted multivariate models demonstrated a marked improvement in the discriminative power of the TIMI UA/NSTEMI model with the incorporation of heart failure and hemodynamic variables. Study limitations included unaccounted for confounders inherent to observational, single institution studies with moderate sample sizes.Conclusions/SignificanceThe GRACE scores provided superior discrimination as compared with the TIMI UA/NSTEMI score in predicting in-hospital and 6-month mortality in UA/NSTEMI patients, although the GRACE and TIMI STEMI scores performed equally well in STEMI patients. The observed discriminative deficit of the TIMI UA/NSTEMI score likely results from the omission of key risk factors rather than from the relative simplicity of the scoring system.

Diagnostic Accuracy of Global Registry of Acute Coronary Events (GRACE) Risk Score in ST-Elevation Myocardial Infarction for In-Hospital and 360-Day Mortality in Japanese Patients

“…19,20,22, 23 In a prior study in USA to validate the accuracy of GRACE 1.0 for in-hospital mortality in 698 STEMI patients, GRACE 1.0 had a high accuracy on ROC analysis, with an AUC as high as 0.84. 17 Although minor differences were observed in some studies, 22 validation studies have confirmed the accurate predictive ability of GRACE 1.0 for short-term mortality.…”

2015 ESC guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation

“…Skala ryzyka GRACE umożliwia najdokładniejszą ocenę ryzyka zarówno przy przyjęciu, jak i przy wypisaniu ze szpitala [92,93]. Kalkulator ryzyka GRACE 2.0 (http:// www.gracescore.org/WebSite/default.aspx?ReturnUrl=%2f) umożliwia bezpośrednie oszacowanie śmiertelności w trakcie pobytu w szpitalu, po 6 miesiącach, po roku i po 3 latach, z pominięciem oceny za pomocą tradycyjnej skali punktowej.…”

Diagnostic accuracy of the TIMI risk score in patients with chest pain in the emergency department: a meta-analysis

“…The study is limited by the relatively small number of studies included in the review and the statistical heterogeneity between studies, which limits the quality of the evidence and our ability to assess publication bias. Although the Global Registry of Acute Coronary Events (GRACE) risk score has been shown to have greater discriminative ability than the TIMI risk score for mortality in-hospital and at six months in patients with confirmed acute coronary syndromes, 25 few studies have assessed the performance of the GRACE score in emergency department patients with potential acute coronary syndromes. One study reported a sensitivity of 100% and a specificity of 13%, with data needed to calculate a complete GRACE score missing for 24% of patients.…”