Impact of CK-MB Testing Policies on Hospital Length of Stay and Laboratory Costs for Patients with Myocardial Infarction Or Chest Pain (Test Utilization and Outcomes‪)‬

Hospitals and their clinical laboratories are under increasing pressure by third-party payers to reduce costs by controlling the utilization of clinical services. Establishment of clinical practice guidelines is one means by which test-ordering patterns for a specific Diagnosis Related Group (DRG) can be standardized. (3) For DRGs that have a heavy laboratory component, clinical scientists should play an active role in establishing efficient testing policies, especially regarding the proper selection of available tests, the manner and frequency of testing, the reporting of turnaround times, and laboratory costs. Hypothesis-driven outcomes research can be helpful in determining how clinical services can be most efficiently delivered. Clinical outcome measures include rates for morbidity, mortality, and disease recurrence as well as quality-of-life assessments. Financial outcomes should be measured from an overall hospital cost for delivery of healthcare and not be isolated to laboratory expenses alone. If studies demonstrate that added tests or greater frequencies of testing lead to better clinical or financial outcomes, utilization of laboratory resources should be increased rather than decreased. The practice of cardiology continues to evolve at a rapid rate, such that utilization of cardiac markers for patients with ischemic heart disease is one area in which outcomes analysis is particularly warranted. Efficient testing policies will have a dramatic effect on costs, given the high number of hospital admissions per year for cardiac patients (700 000 for Medicare alone). Moreover, Medicare weighting factors for cardiac DRGs (Table 1) are among the highest of all medical DRGs listed by the Health Care Financing Administration (HCFA) [1]. The clinical chemistry laboratory has traditionally played a large role in triage, diagnosis, and management of coronary artery disease. The assay for creatine kinase (CK) MB isoenzyme has become standard practice for serologic diagnosis of acute myocardial infarction (AMI). Guidelines established by the American College of Physicians recommend use of CK and lactate dehydrogenase isoenzymes at admission and at 12 and 24 h after admission [2]. In uncomplicated AMI cases, activities of total CK and CK-MB increase and return to normal limits within 3-4 days, usually before the patient has been discharged. Some AMI patients, however, develop complications--e.g., congestive heart failure, postinfarction angina, cardiogenic shock, and reinfarction-either while hospitalized or within a few weeks or months after discharge [3-5]. Thus, it is typical practice for cardiologists to continue ordering assays of total CK and CK-MB until the day of discharge. Some laboratories have elected to use myoglobin or CK-MB isoforms to detect new injury attributable to complications, because these markers rapidly return to normal after the initial insult [6, 7]; however, use of these markers is not yet as widespread as CK-MB testing. Although not specifically documented, lactate dehydrogenase isoenzymes and cardiac troponins T and I are not likely to be as useful as CK-MB for detecting postinfarction ischemia because their concentrations remain abnormally high for a week or more after AMI, obscuring the release of proteins and enzymes from any subsequent injury [8,91.