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HomeEmergency MedicineSimple laboratory score – a safer, faster way to diagnose heart attacks

Simple laboratory score – a safer, faster way to diagnose heart attacks

An international team of researchers has developed a simple laboratory score that is safer and faster at diagnosing patients who visit the emergency department with heart attack symptoms. The score can also identify patients at risk of subsequent heart issues after discharge.

"We have developed a simple lab score that is superior to using cardiac troponin alone for the identification of patients at low and high risk for heart attack or death at emergency department presentation," says Dr Peter Kavsak, McMaster University, Hamilton, Ontario. According to Professor Andrew Worster, also from McMaster University, "This lab score may reduce both the number of blood tests and time spent in the emergency department for chest pain patients."

Patients with chest pain symptoms require multiple blood tests over several hours before a diagnosis is reached. Previous studies using high-sensitivity cardiac troponin alone to rule out and rule in heart attacks have not consistently demonstrated sufficient safety to use in clinical practice.

In this international study, researchers from Canada, Australia, New Zealand and Germany combined common laboratory blood tests available at many hospitals around the world to create a single laboratory score, or clinical chemistry score, to diagnose heart attack. These blood tests are part of the World Health Organisation's list of essential in vitro diagnostics tests for health care facilities with clinical laboratories.

The researchers validated the clinical chemistry score as a predictor of heart attack or death within 30 days using data on 4245 patients from emergency department studies in the four countries. Within one month of the emergency department visits, 727 heart attacks or death in patients occurred. A negative (or low-risk) clinical chemistry score at emergency department presentation missed only one of these events compared with up to 25 missed heart attacks/death when using a high-sensitivity cardiac troponin test alone. A positive (or high-risk) clinical chemistry score also identified about 75% of patients at high risk of heart attack or death when positive compared with a low of 40% detected when the high-sensitivity cardiac troponin test alone was positive. The clinical chemistry score worked equally well in men and women.

The authors suggest the score can be useful for standardising diagnoses and improving safety.

"Adoption of the clinical chemistry score algorithm would standardize reporting of high-sensitivity cardiac troponin test results, how the tests are interpreted in the normal range, and represent an option less susceptible to both analytical and preanalytical errors. This could result in the safest laboratory approach for physicians to use at presentation in the emergency department," says Kavsak.

The Canadian Institutes of Health Research funded the study with reagent support from Abbott Laboratories and Roche Diagnostics.

Abstract
Background: Testing for high-sensitivity cardiac troponin (hs-cTn) may assist triage and clinical decision-making in patients presenting to the emergency department with symptoms of acute coronary syndrome; however, this could result in the misclassification of risk because of analytical variation or laboratory error. We sought to evaluate a new laboratory-based risk-stratification tool that incorporates tests for hs-cTn, glucose level and estimated glomerular filtration rate to identify patients at risk of myocardial infarction or death when presenting to the emergency department.
Methods: We constructed the clinical chemistry score (CCS) (range 0–5 points) and validated it as a predictor of 30-day myocardial infarction (MI) or death using data from 4 cohort studies involving patients who presented to the emergency department with symptoms suggestive of acute coronary syndrome. We calculated diagnostic parameters for the CCS score separately using high-sensitivity cardiac troponin I (hs-cTnI) and high-sensitivity cardiac troponin T (hs-cTnT).
Results: For the combined cohorts (n = 4245), 17.1% of participants had an MI or died within 30 days. A CCS score of 0 points best identified low-risk participants: the hs-cTnI CCS had a sensitivity of 100% (95% confidence interval [CI] 99.5%–100%), with 8.9% (95% CI 8.1%–9.8%) of the population classified as being at low risk of MI or death within 30 days; the hs-cTnT CCS had a sensitivity of 99.9% (95% CI 99.2%–100%), with 10.5% (95% CI 9.6%–11.4%) of the population classified as being at low risk. The CCS had better sensitivity than hs-cTn alone (hs-cTnI < 5 ng/L: 96.6%, 95% CI 95.0%–97.8%; hs-cTnT < 6 ng/L: 98.2%, 95% CI 97.0%–99.0%). A CCS score of 5 points best identified patients at high risk (hs-cTnI CCS: specificity 96.6%, 95% CI 96.0%–97.2%; 11.2% [95% CI 10.3%–12.2%] of the population classified as being at high risk; hs-cTnT CCS: specificity 94.0%, 95% CI 93.1%–94.7%; 13.1% [95% CI 12.1%–14.1%] of the population classified as being at high risk) compared with using the overall 99th percentiles for the hs-cTn assays (specificity of hs-cTnI 93.2%, 95% CI 92.3–94.0; specificity of hs-cTnT 73.8%, 95% CI 72.3–75.2).
Interpretation: The CCS score at the chosen cut-offs was more sensitive and specific than hs-cTn alone for risk stratification of patients presenting to the emergency department with suspected acute coronary syndrome.

Authors
Peter A Kavsak, Johannes T. Neumann, Louise Cullen, Martin Than, Colleen Shortt, Jaimi H Greenslade, John W Pickering, Francisco Ojeda, Jinhui Ma, Natasha Clayton, Jonathan Sherbino, Stephen A Hill, Matthew McQueen, Dirk Westermann, Nils A Sörensen, William A Parsonage, Lauren Griffith, Shamir R Mehta, PJ Devereaux, Mark Richards, Richard Troughton, Chris Pemberton, Sally Aldous, Stefan Blankenberg, Andrew Worster

[link url="https://www.sciencedaily.com/releases/2018/08/180820085203.htm"]Canadian Medical Association material[/link]
[link url="http://www.cmaj.ca/content/190/33/E974"]Canadian Medical Association Journal abstract[/link]

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