High-sensitivity cardiac troponin I vs a clinical chemistry score for predicting all-cause mortality in an emergency department population

Background — For patients investigated for suspected acute coronary syndrome there is uncertainty if a single measurement of high-sensitivity cardiac troponin I (hs-cTnI) at emergency department (ED) presentation can identify patients at both low- and high-risk for mortality.

Methods — We included consecutive adult ED patients who had a clinical chemistry score (CCS) taken at presentation (i.e. combination of glucose, creatinine (for estimated glomerular filtration rate determination), and hs-cTnI assay) in a Canadian city between 2012 and 2013. Outcomes were 3-month, 1-year and 5-year all-cause mortality using the provincial death registry. Mortality rates and test performance (e.g., sensitivity and specificity) with 95% confidence intervals (95%CI) were obtained for the CCS or hs-cTnI assay alone using established cutoffs for these tests.

Results — Our cohort included 5,974 patients with a 1-year mortality rate of 17.2% (95%CI:16.2-18.3). A CCS ≥1 yielded a sensitivity of 99.2% (95%CI:98.4-99.6) as compared to the hs-cTnI ≥5 ng/L cutoff sensitivity of 88.4% (95% CI: 86.3-90.3), with the mortality rate being significantly lower for patients with CCS <1 (2.0%; 95%CI:0.9-4.0) versus patients with hs-cTnI <5 ng/L (5.0%; 95%CI:4.2-6.0) at 1-year (p=0.01). A CCS = 5 also yielded a higher specificity (88.5%; 95%CI:87.5-89.3) as compared to hs-cTnI >26 ng/L (83.9%; 95%CI: 82.9-84.9), with no difference in mortality rates (37.4% vs. 36.3%; p=0.66). This trend was consistent at 3-months and 5-year mortality.

Conclusion — For ED patients with a potential cardiac issue, using the CCS cutoffs can better identify patients at low- and high-risk for mortality than utilizing published cutoffs for hs-cTnI alone.