Clinicians ignore best practice guidelines: Prospective audit of cardiac injury marker ordering in patients with chest pain

BACKGROUND: Chest pain is a frequent presenting symptom and is a diagnostic challenge. Recent recommendations state that high-sensitivity cardiac troponin assays are the only biochemical test required in the diagnosis of acute coronary syndrome (ACS) and that other biomarkers such as myoglobin or creatine kinase (CK)-MB isoform are not indicated. OBJECTIVE: To establish whether clinician ordering in the setting of suspected ACS was in keeping with recent recommendations. METHODS: A prospective audit was undertaken of all requests for cardiac troponin I (cTnI) and CK-MB received at a large tertiary hospital in Durban, South Africa, during a 20-day period in December 2012. RESULTS: A total of 193 cardiac marker requests were received: 12 (6.2%) requests were for cTnI alone; 8 (4.1%) were for CK-MB alone; and the remaining 173 (89.7%) were for both cTnI and CK-MB. Therefore, a total of 181 (93.8%) incorrect requests were received during this period. A total of 103 (53.4%) patients had values below the cut-off point of 40 ng/l for cTnI, i.e. ACS was ruled out. Of these, 15 had CK-MB values above the reference interval. A total of 12 (6.2%) patients had cTnI values > 500 ng/l, i.e. ACS was ruled in; 33.3% of this group had normal CK-MB values. CONCLUSION: Ordering patterns in the setting of ACS did not reflect current recommendations and were wasteful and potentially dangerous.