Biochemical markers of myocardial injury test turnaround time: a College of American Pathologists Q-Probes study of 7020 troponin and 4368 creatine kinase-MB determinations in 159 institutions.

CONTEXT

Rapid diagnosis of acute myocardial infarction in patients presenting to emergency departments (EDs) with chest pain may determine the types, and predict the outcomes of, the therapy those patients receive. The amount of time consumed in establishing diagnoses of acute myocardial infarction may depend in part on that consumed in the generation of the blood test results measuring myocardial injury.

OBJECTIVE

To determine the normative rates of turnaround time (TAT) for biochemical markers of myocardial injury and to examine hospital and laboratory practices associated with faster TATs.

DESIGN

Laboratory personnel in institutions enrolled in the College of American Pathologists Q-Probes Program measured the order-to-report TATs for serum creatine kinase-MB and/or serum troponin (I or T) for patients presenting to their hospital EDs with symptoms of acute myocardial infarction. Laboratory personnel also completed detailed questionnaires characterizing their laboratories' and hospitals' practices related to testing for biochemical markers of myocardial injury. ED physicians completed questionnaires indicating their satisfaction with testing for biochemical markers of myocardial injury in their hospitals.

SETTING

A total of 159 hospitals, predominantly located in the United States, participating in the College of American Pathologists Q-Probes Program.

RESULTS

Most (82%) laboratory participants indicated that they believed a reasonable order-to-report TATs for biochemical markers of myocardial injury to be 60 minutes or less. Most (75%) of the 1352 ED physicians who completed satisfaction questionnaires believed that the results of tests measuring myocardial injury should be reported back to them in 45 minutes or less, measured from the time that they ordered those tests. Participants submitted TAT data for 7020 troponin and 4368 creatine kinase-MB determinations. On average, they reported 90% of myocardial injury marker results in slightly more than 90 minutes measured from the time that those tests were ordered. Among the fastest performing 25% of participants (75th percentile and above), median order-to-report troponin and creatine kinase-MB TATs were equal to 50 and 48.3 minutes or less, respectively. Shorter troponin TATs were associated with performing cardiac marker studies in EDs or other peripheral laboratories compared to (1) performing tests in central hospital laboratories, and (2) having cardiac marker specimens obtained by laboratory rather than by nonlaboratory personnel.

CONCLUSION

The TAT expectations of the ED physicians using the results of laboratory tests measuring myocardial injury exceed those of the laboratory personnel providing the results of those tests. The actual TATs of myocardial injury testing meet the expectations of neither the providers of those tests nor the users of those test results. Improving TAT performance will require that the providers and users of laboratory services work together to develop standards that meet the needs of the medical staff and that are reasonably achievable by laboratory personnel.