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LONDON -- High sensitivity-troponin I allowed discharge or diagnosis of acute myocardial infarction (MI) in 1 hour without greater risk than the standard 3-hour assay, the BACC trial showed.

The 38% of patients who could have been discharged based on levels under 6 ng/L initially and at 1 hour were no more likely to have non-ST-segment MI (NSTEMI) missed than were patients discharged based on the conventional 3-hour algorithm in accordance with European Society of Cardiology guidelines.

The negative predictive value was 99.0% compared with 99.5% for the 3-hour algorithm, with sensitivities of 97.6% versus 98.8%, respectively. Neither difference was statistically significant.

Ruling-in NSTEMI based on levels over 6 ng/L that rose at least 12 ng/L by 1 hour also had a specificity and positive predictive value as good as that based on assessment over 3 hours, without significant differences.

"There's no need to wait for 3 hours," , of the University Heart Centre Hamburg and the German Centre for Cardiovascular Research in Hamburg, Germany, said at a press conference where he presented the Hot Line trial results here at the European Society of Cardiology meeting.

for assessment of suspected NSTEMI using the 99th percentile of the upper reference level (in this case 27 ng/L) as a cutoff.

"More rapid rule-outs would be helpful in terms of the cost of medical care, particularly in our ERs in the United States," , of Rush University in Chicago and president of the American College of Cardiology, told 番茄社区 at the press conference he co-chaired.

A 1-hour algorithm hasn't gotten much uptake in U.S. emergency departments, largely because of the guidelines, noted , of New York-Presbyterian Hospital/Columbia University Medical Center in New York City.

"There certainly is interest in trying to more expeditiously move people out of the emergency room who don't need to be in the emergency room," he told 番茄社区. "So this is potentially an exciting advance."

The Biomarkers in Acute Cardiovascular Care (BACC) study included 1,045 patients with acute chest pain suggestive of acute MI with HS-troponin T measured at 0 and 3 hours after admission along with the usual clinical work-up but who also, for study purposes, got HS-troponin I measured at 0, 1, and 3 hours.

Among them, 184 had NSTEMI and 793 had no acute MI. STEMI was excluded because it is an ECG-based diagnosis, not assay-based.

The study also compared the threshold for HS-troponin I it identified as optimally predictive (9 ng/L) to the 99th percentile-based cutoff recommended by guidelines (27 ng/L). The lower threshold had a significant advantage in negative predictive value at both the 1- and 3-hour assessments.

When the findings were validated in two independent cohorts, the results were fairly similar.

Mortality over the subsequent 6 montHS in the patients showed low risk for patients who would have been ruled out based on the 1-hour algorithm.

"Importantly those patients labeled as grey zone patients -- so they didn't fit the non-STEMI rule-in or the rule out group, they had elevated troponin levels without the sufficient dynamics to be ruled in -- had the highest mortality," Westermann said. "Therefore, it is of the utmost importance to further evaluate those patients that can't be discharged immediately, and probably they need specific medical treatment."

That group comprised nearly half of the cohort.

Analysis in a 74,738-individual general population cohort without prevalent cardiovascular diseased confirmed that the 9 ng/L cutoff was more prognostic of 1- and 5-year mortality than the 99th percentile cutoff (both P<0.001).

In terms of generalizability, "one thing that is very striking is the mean age was actually quite young compared with the patients we're seeing in the U.S., which is around 63," Williams noted.

"I'm not sure that would change the results but the comorbid conditions that increase the troponins, whether it's renal failure, sepsis, or other conditions we're seeing more in the United States, might make it important to focus on that delta that he showed of 12 ng/L," he added.

A poster presentation at the conference detailed just how much impact the conditions have on troponin results. In an analysis of more than 93,439 clinical encounters at 13 hospitals in one large health system from June 2013 to June 2014, primary encounter diagnoses associated with high rates of positive troponins included:

• Cerebrovascular accident (10% of 865)
• Septicemia (26% of 1,976)
• Acute respiratory failure (28% of 626)

Notably, "83% of positive troponins in our study were associated with a primary non-acute coronary syndromes (ACS) diagnosis," whereas there are no guidelines supporting use outside of suspected ACS, reported , and , both of the Baylor Scott & White Healthcare System in Dallas.

"Troponin is being tested often and in clinical scenarios unlikely to represent ACS/MI," he told 番茄社区. "With the FDA prepared to approve HS-troponin testing in the U.S., we are concerned that current testing patterns may lead to a tsunami of 'positive' testing and resulting downstream cardiac consultation and testing."

Williams suggested that the BACC data would inform future guidelines, although Stone suggested that the algorithm would likely need to be validated in a large U.S. database to confirm generalizability before any sea change occurs.