A single measurement of the new high-sensitivity cardiac troponin T (hs-cTnT) and a normal electrocardiogram (ECG) might help doctors predict which patients with chest pain are at low risk of heart attack and can be sent home from the emergency department (ED), a study has shown.

Researchers in Sweden sought to determine the negative predictive value of undetectable hs-cTnT (<5 ng/L) and an ECG without significant ST elevation or depression for the primary endpoint of myocardial infarction (MI) within 30 days among 14,636 patients (age >25 years) with chest pain who presented at the ED of a hospital in Sweden over a 2-year period. [Abstract 403-14-LB-13200; J Am Coll Cardiol 2014; doi:10.1016/j.jacc.2014.03.017]

Nearly 9,000 patients (61 percent) who had undetectable hs-cTnT (<5 ng/L) on initial testing (as measured with Elecsys® 2010, Roche Diagnostics) were included in the study. They were younger and less likely to have diabetes, chronic kidney disease, prior MI or stroke compared with patients who had increased hs-cTnT levels (5-14 and >14 ng/L).

Hospitalization rates were lower among patients with undetectable hs-cTnT (21 percent vs 44 and 82 percent for 5-14 and >14 ng/L, respectively). Diagnosis of MI increased with increasing levels of hs-cTnT (2 percent for <5 ng/L, 3.1 percent for 5-14 ng/L, 4.1 percent for >14 ng/L).

Within 30 days, 39 patients with undetectable hs-cTnT had MI (24 had significant ECG changes, 15 had normal ECG). The negative predictive value of the tests for MI was 99.8 percent (95% CI, 99.7-99.9) and 100 percent for death (95% CI, 99.9-100). After adjusting for age, sex, diabetes, prior MI and eGFR, there was no significant difference in the risk of death between patients discharged from the ED and those hospitalized within 365 days (hazard ratio [HR], 0.73; 955 CI, 0.48-1.12).

“Patients with chest pain who have an initial hs-cTnT of <5 ng/L and no signs of ischemia on ECG, independent of duration of chest pain and other risk factors, have a minimal risk of MI within 30 days, and no risk of death,” said lead investigator Dr. Nadia Bandstein from the Karolinska Institute in Stockholm, Sweden. “These patients can be safely discharged from the ED.”

The study has some clinical implications – it can reduce overcrowding of the ED, prevent unnecessary admissions, and save doctor-patient time. If MI can be ruled out more quickly, 20 to 25 percent of all hospital admissions for chest pain can be prevented, Bandstein said.

Panelist Dr. Allan Jaffe from Mayo Clinic, Rochester, Minnesotta, US, however, cautioned that the assay is likely to be effective only in low-risk groups. “We have to be careful in defining how we rule people in and out. In the long run, we will be able to validate the strategy… we need to do it a little bit more rigorously.”