Clinical and financial impact of removing creatine kinase-MB from the routine testing menu in the emergency setting

Cardiac troponins T and I have replaced creatine kinase-MB (CK-MB) as the criterion standard for diagnosing myocardial injury. However, many laboratories still routinely perform a high volume of CK-MB testing in conjunction with troponin.

The purpose of this study is to study the clinical and financial impact of removing CK-MB from the routine emergency department (ED) test menu at a large academic medical center.

Creatine kinase-MB was removed from ED ordering templates and laboratory requisitions (ie, intervention), although the test could still be manually ordered. Data for creatine kinase (CK), CK-MB, and troponin T (TnT) specimens ordered during a 12-month period (6 months preintervention and 6 months postintervention) (n = 14571) was downloaded from our laboratory information system. All specimens with (1) normal TnT (ie, <0.01 ng/mL), (2) elevated CK-MB (ie, >6.6 ng/mL), and (3) elevated CK-MB index (ie, >5) were considered discrepant and independently reviewed by 2 ED clinicians for the presence of an acute coronary syndrome and for documentation of final diagnosis. Creatine kinase, CK-MB, and TnT ED volumes preintervention and postintervention were analyzed to assess laboratory cost savings.

Of the 6444 cases included in the analysis, only 17 were discrepant. Of all 17 cases, no patients were diagnosed with acute coronary syndrome. After removing CK-MB from the templates and requisitions, CK-MB and CK volumes decreased by 80% and 76%, respectively, translating to annual reagent cost savings of approximately $47000.

Creatine kinase-MB can be removed from the routine ED test menu without adversely affecting patient care. In addition, substantial cost savings can be achieved by reducing unnecessary CK-MB testing and associated CK orders.