High-sensitivity Troponin Testing May Prevent Unnecessary Admissions for Chest Pain

WASHINGTON, DC—In patients presenting to the emergency department (ED) with chest pain, utilization of high-sensitivity (hs) cardiac troponin T testing in conjunction with an electrocardiogram can help predict patients at low risk of death or myocardial infarction (MI) who can be safely discharged, according to a study presented March 30, 2014, at the American College of Cardiology/i2 Scientific Session. The findings, simultaneously published online ahead of print in the Journal of the American College of Cardiology, have implications for reducing hospital admissions, ED overcrowding, and costs.

Investigators led by Nadia Bandstein, MD, of Karolinska Institute (Solna, Sweden), retrospectively studied 8,907 patients reporting to the ED at their institution with chest pain between 2010 and 2012 who had at least 1 hs troponin T level measured and analyzed with the Elecsys 2010 (Roche Diagnostics GmbH, Mannheim, Germany).

Lower Level, Lower Risk

Levels of first hs troponin T in the cohort were:

• < 5 ng/l in 61%
• 5-14 ng/l in 21%
• > 14 ng/l in 18%

Patients with a first hs troponin T level of < 5 ng/l were younger, less likely to have chronic kidney disease, chronic cardiovascular disease, or diabetes, and less likely to be taking medication for secondary prevention of cardiovascular disease. Patients with increased levels were older, more often men, and had more comorbidities.

Hospitalization rates were 21% in patients with a first hs troponin T level < 5 ng/l, 44% for measurements of 5-14 ng/l, and 82% for level > 14 ng/l.

The most common discharge diagnoses in patients with a first hs troponin measurement < 5 ng/l were nonspecific chest pain (50.0%), A-fib or supraventricular tachycardia (5.6%), and angina (5.1%). Diagnosis of MI increased with increasing levels of first hs troponin T:

• < 5 ng/l (2.0%)
• 5-14 ng/l (3.1%)
• > 14 ng/l (4.1%)

Overall, 40 patients in the group with the lowest troponin T levels were diagnosed with MI within 30 days. Of these, 24 had significant ECG changes; 15 were diagnosed with STEMI and 9 were diagnosed with non-STEMI. No patient had evidence of left bundle branch block on ECG.

Patients diagnosed with STEMI or non-STEMI despite no significant ST-elevation or depression on first ECG were older, more often men, and were more likely to have had prior cardiovascular disease than patients with hs troponin T < 5 ng/l and no MI. In addition, 40% of these patients were active smokers.

A first hs troponin T level < 5 ng/l in combination with no signs of ischemia on ECG carried a negative predictive value for MI of 99.8% (95% CI 99.7-99.9) and an absolute risk for MI of 0.17% (95% CI 0.09-0.27). The negative predictive value for death within 30 days was 100%. There was no significant difference in the risk of death within 365 days between those who were discharged directly from the ED and those who were admitted to the hospital after adjustment for age, sex, diabetes, prior MI, and eGFR (HR 0.73; 95% CI 0.48-1.12).

Implications for Reducing Admissions

According to Dr. Bandstein and colleagues, 594 patients with a first hs troponin T reading of < 5 ng/Lwould have to be admitted to detect 1 additional MI. Furthermore, they say hospitalization could have been avoided in the majority of these patients, resulting in an annual decrease of 500-1,000 admissions to their hospital. The potential savings for healthcare providers, they add, are enormous.

“We believe that we may prevent 20-25% of all hospital admissions for chest pain,” Dr. Bandstein said, adding that this represents 600-700 patients per year at her institution.

Regarding the 15 patients diagnosed with STEMI despite having an undetectable first hs troponin T level combined with no signs of ischemia on the intial ECG, Dr. Bandstein and colleagues contend that if a second level had been obtained 3-4 hours after symptom onset, significant elevation likely would have been seen in most patients.

‘Straws in the Wind’

Because hs troponin T can detect minimally increased levels of troponins several hours before older troponin assays, repeated measurements may not be necessary. However, panelist Allan S. Jaffe, MD, of Mayo Clinic (Rochester, MN), cautioned that it is still early to make too many assumptions about the ability of hs troponin T assays to broadly rule out MI.

“It’s important [to recognize] that this strategy is likely effective in only the low-risk groups,” Dr. Jaffe said. He added that it is unclear how many samples were taken from each patient acutely or what the criteria were among treating physicians for ultimately ruling out MI (ie, where and how clinical judgment fit in the process).

“There are straws in the wind that this strategy will work. I just think we have to be terribly careful here in defining both how we rule people in and rule people out,” Dr. Jaffe said. “I think in the long run we will be able to validate the strategy. I just think we need to do it a little bit more rigorously.”

Source:Bandstein N. Undetectable high sensitivity cardiac troponin t level in the emergency department and risk of myocardial infarction.
Presented at: American College of Cardiology/i2 Scientific Session; March 30, 2014; Washington, DC.

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