A new chest pain strategy in Thunder Bay

Diagnostic parameters of CK–MB and myoglobin related to chest pain duration

Objective:

Cardiac marker sensitivity depends on chest pain duration at the time of sampling. Our objective was to estimate the sensitivity, specificity, and likelihood ratios of early CK–MB and myoglobin assays in patients presenting to the emergency department (ED) with nondiagnostic ECGs, stratified by the duration of ongoing chest pain at the time of ED assessment.

Methods:

This was a prospective observational study carried out in 10 US and 2 Canadian EDs. Patients >25 years of age with ongoing chest pain and nondiagnostic ECGs were stratified by pain duration (0–4 h, 4–8 h, 8–12 h, >12 h). CK–MB and myoglobin assays were drawn at T = 0 (ED assessment) and T = 1 hr. Patients were followed for 7–14 days to identify all cases of acute myocardial infarction (AMI). ED test results were correlated with patient outcomes.

Results:

Of 5005 eligible patients, 565 had AMI. Pain duration was 0–4 h in 3014 patients, 4–8 h in 961, 8–12 h in 487, and >12 h in 543. Marker sensitivity increased with pain duration, ranging from 28%–77% for CK–MB and 39%–73% for myoglobin. The maximal sensitivity achieved by a T = 0 assay was 73%, and this was in patients with 8–12 or >12 h of ongoing pain. No combination of tests achieved 90% sensitivity in any pain duration strata.

Conclusions:

Regardless of chest pain duration, single assays and early serial markers (0+1 hr) do not rule out AMI; therefore, serial assays over longer observation periods are required. Likelihood ratios derived in this study will help physicians who use Bayesian analysis to determine post-test AMI likelihood in patients with chest pain.

Cardiac markers and their point-of-care testing for diagnosis of acute myocardial infarction

Acute myocardial infarction (AMI) is the world's leading cause of mortality and morbidity. Therefore, quick and reliable diagnostics of AMI is extremely critical. Compared to the traditionally used central laboratory tests (CLT), which can be time-consuming and expensive, point-of-care testing (POCT) for AMI-indicative cardiac markers provides a convenient means for rapid diagnostic assays to be performed at the site of patient care delivery. In this article, the etiology and diagnosis of AMI are introduced, and some typical cardiac markers and their clinical applications are reviewed. Furthermore, the various POC cardiac marker devices that are currently available, the benefits of using cardiac marker POC assays, and challenges that cardiac marker POCT are facing are also discussed.

Cardiac markers and point-of-care testing: a perfect fit

Biochemical markers are of increasing importance in diagnostic strategies for ruling in and ruling out acute myocardial infarction (AMI), particularly when electrocardiographic (ECG) findings do not allow a diagnosis. Point-of-care testing (POCT) or "near-patient" testing allows for diagnostic assays to be performed at the site of patient care delivery. The biochemical markers that are commonly used by physicians to aid in the diagnosis of AMI are myoglobin, CK-MB, troponin I, and troponin T. Currently available POCT assays possess comparable diagnostic performance to laboratory-based cardiac marker assays. This provides an opportunity for POCT to evolve into the standard of care for evaluating the greater than 6 million American patients presenting with chest discomfort. Full acceptance of this relatively new technology will not be realized until users reach a comfort level where utilization of these devices is foolproof and they have faith in the results.

Recommendations and opinions for the use of point-of-care testing for hospitals and primary care: summary of a 1999 symposium

As part of a symposium on laboratory medicine, a colloquium on point-of-care testing was held in June 1999 where four experts were invited to produce recommendations and opinions on the use of point-of-care testing under various clinical venues. Each commented on costs for providing POCT services. A total of eleven recommendations and four opinions were rendered and discussed in an open forum. While one expert concluded that some forms of POCT are less expensive than central laboratory testing if entire laboratory workstations are eliminated, another expert suggested that POCT offered little advantage if rapid transport systems are available. A recommendation was made that POCT be considered for analytes that have a required reporting turnaround time of <30 min, and that the goals for precision and accuracy should be dictated by the clinical need and not by analytical limitations. Recommendations for POCT in specific clinical situations include use of glycated hemoglobin and urine albumin testing with personal glucose monitoring at the time of consultation, use of glycated albumin for gestational diabetes, leukocyte esterase and nitrite testing in urine to screen for urinary tract infections, coagulation tests for monitoring patients on oral anticoagulant therapy and in the operating room, testing for H. pylori for patients with dyspepsia, and cardiac markers and urine drugs-of-abuse testing in the emergency department.

Commentary: Chest pain evaluation in the emergency department

In this issue, Dr. David Mutrie illustrates both the utility of departmental care protocols and the caution we must take in drawing conclusions from them. The latter point is particularly important if one wishes to apply these conclusions to other institutions.

The Thunder Bay Regional Hospital (TBRH), in Ontario, established simple guidelines for the management of patients with chest pain. Following the implementation of these guidelines, Mutrie reports shorter chest pain assessment times and reduced admission rates for non-myocardial infarction and non-unstable angina patients, without any obvious increase in inappropriate discharge of patients with ischemic disease. Can we therefore conclude that the guidelines were responsible for these improvements and that this set of guidelines would similarly improve performance in other emergency departments? The answer, unfortunately, is No. The fact is, the establishment of any organized approach to a clinical problem tends to improve performance. This is perhaps a sad reflection on “individual” practice patterns, but it is true nonetheless.