Are Point-of-Care Cardiac Markers Useful for Early Diagnosis of MI in the ED?

Point-of-care cardiac biomarkers can be used to diagnose MI within a few hours of presentation to the emergency department (ED). The combination of troponin, myoglobin, and CK-MB measured at baseline and 90-120 minutes later has been shown to have high sensitivity but poor specificity(1-9), such that this combination can rule out MI in only a minority of patients, with most requiring further testing. The most recent study(9) suggested that myoglobin and CK-MB did not improve diagnostic accuracy beyond troponin alone. Using troponin alone could therefore allow MI rule-out in a greater proportion of patients.

Myoglobin and CK-MB gradient measurement was originally used to improve detection of MI shortly after symptom onset, when troponin sensitivity is suboptimal. Modern high-sensitivity troponin assays appear to have superior early sensitivity to myoglobin and CK-MB.(10,11) However, only one point-of-care system currently has data available to show that it meets acceptable performance criteria (accurate at the 99th percentile with the ability to detect a significant change).(12,13) Thus, for most point-of-care systems, the potential for reduced times to decision-making needs to be weighed against a loss of sensitivity when compared to laboratory assays.

Even if point-of-care testing can accurately diagnose MI in the ED, it is not clear that this will consistently lead to worthwhile changes in patient care, improved effectiveness or cost-effectiveness. Randomized trials of point-of-care cardiac markers in the ED have shown that reduced turnaround times can lead to reduced time to anti-ischemic treatment and need for hospital admission(15), but affects on admission and length of stay were inconsistent and varied between centers.(16,17) Where hospital admission rates were reduced this did not lead to reduced health care resource use, and costs may even have been increased.(18)


References

  1. McCord J, Nowak RM, McCullough PA et al. Ninety-minute exclusion of acute myocardial infarction by use of quantitative point-of-care testing of myoglobin and troponin I. Circulation. 2001;104:1483-8.
  2. Apple FS, Christensen RH, Valdes R et al. Simultaneous rapid measurement of whole blood myoglobin, creatinine kinase MB and cardiac troponin I by the Triage cardiac panel for detection of myocardial infarction. Clin Chem. 1999;45:199-205.
  3. Newby LK, Storrow AB, Gibler WB et al. Bedside multimarker testing for risk stratification in chest pain units: The CHECKMATE Study. Circulation. 2001;103:1832-7.
  4. Caragher TE, Fernandez BB, Jacobs FL & Barr LA. Evaluation of quantitative cardiac biomarker point of care testing in the emergency department. J Emerg Med. 2002;22:1-7.
  5. Ng SM, Krishnaswamy P, Morissey R et al. Ninety-minute accelerated critical pathway for chest pain evaluation. Am J Cardiol. 2001;88:611-7.
  6. Hamilton AJ, Swales LA, Neill J, Murphy JC, Darragh KM, Rocke LG, Adgey J. Risk stratification of chest pain patients in the emergency department by a nurse utilizing a point of care protocol. Eur J Emerg Med. 2008;15:9-15.
  7. Rathore S, Knowles P, Mann APS, Dodds PA. Is it safe to discharge patients from accident and emergency using a rapid point of care Triple Cardiac Marker test to rule out acute coronary syndrome in low to intermediate risk patients presenting with chest pain? Eur J Int Med. 2008;19:537-540.
  8. Straface AL, Myers JH, Kirchick HJ, Blick KE. A Rapid Point-of-Care Cardiac Marker Testing Strategy Facilitates the Rapid Diagnosis and Management of Chest Pain Patients in the Emergency Department. Am J Clin Pathol. 2008;129:788-795.
  9. Than M, Cullen L, Reid CM, et al. A 2-h diagnostic protocol to assess patients with chest pain symptoms in the Asia-Pacific region (ASPECT): a prospective observational validation study. Lancet. 2011;377:1077-1084.
  10. Reichlin et al. Early diagnosis of myocardial infarction with sensitive cardiac troponin assays. N Engl J Med. 2009;361:858-67.
  11. Keller et al. Sensitive troponin I assay in early diagnosis of acute myocardial infarction N Engl J Med. 2009;361:868-72.
  12. Christenson RH, Collinson PO. Point-Of-Care Testing in Acute Coronary Syndromes, Heart Failure, Stroke and Venous Thromboembolism. Is There Evidence of "A Need for Speed". In Point-of-Care Testing. Needs, Opportunity and Innovation. 3rd edition. Price CP, St John A, Kricka LJ (eds). AACC press, Washington, DC. 2010. 503-517.
  13. Apple FS. A new season for cardiac troponin assays: it's time to keep a scorecard. Clin Chem. 2009;55:1303-6.
  14. Renaud B, Maison P, Ngako A, Cunin P, Santin A, Hervé J, Salloum M, Calmettes M-J, Boraud C, Lemiale V, Grégo JC, Debacker M, Hémery F, Roupie E. Impact of Point-of-care Testing in the Emergency Department Evaluation and Treatment of Patients with Suspected Acute Coronary Syndromes. Acad Emerg Med. 2008;15:216–224,
  15. Goodacre SW, Bradburn M, Cross E, Collinson PO, Gray A, Hall AS on behalf of the RATPAC research team. The RATPAC Trial (Randomised Assessment of Treatment using Panel Assay of Cardiac markers): A randomised controlled trial of point-of-care cardiac markers in the emergency department. Heart. 2011;97:190-196.
  16. Ryan RJ, Lindsell CJ, Hollander JE, O’Neil B, Jackson R, Schreiber D, Christenson R, Gibler WB. A Multicenter Randomized Controlled Trial Comparing Central Laboratory and Point-of-Care Cardiac Marker Testing Strategies: The Disposition Impacted by Serial Point of Care Markers in Acute Coronary Syndromes (DISPO-ACS) Trial. Ann Emerg Med. 2009;53:321-8.
  17. Bradburn M, Goodacre S, Fitzgerald P, Coats TJ, Gray AJ, Hassan TB, Humphrey J, Kendall JM, Smith J, Collinson P. Inter-hospital variation in the RATPAC Trial (Randomised Assessment of Treatment using Panel Assay of Cardiac markers). Emerg Med J. 2011, Published Online First: 26 May 2011 doi:10.1136/emj.2010.108522.
  18. Fitzgerald P, Goodacre SW, Cross E, Dixon S. Cost-effectiveness of point-of-care biomarker assessment for suspected myocardial infarction: The RATPAC Trial (Randomised Assessment of Treatment using Panel Assay of Cardiac markers). Acad Emerg Med. 2011;18:488-495.

Keywords: Biological Markers, Creatine Kinase, MB Form, Emergency Service, Hospital, Myoglobin, Sensitivity and Specificity, Troponin


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