Financial impact of a rapid CK-MB-specific immunoassay on the diagnosis of myocardial infarction. The purpose of this study was twofold. First, we evaluated the financial impact of a rapid, monoclonal antibody-based CK-MB mass assay (Stratus, Dade Division, Baxter Laboratories, Miami, Fla) for the direct measurement of CK-MB in serum samples from 65 patients admitted to the coronary care unit with the possible diagnosis of acute myocardial infarction. Second, we evaluated retrospectively the Stratus assay and an activity assay (electrophoresis) for CK-MB in the following patient categories: acute myocardial infarction treated with and without thrombolytic therapy, angina, congestive heart failure, skeletal muscle trauma, and the acutely ill without acute myocardial infarction. The advantageous features of the Stratus mass assay were as follows. First, the laboratory was able to perform the assay more frequently because of the short assay time per specimen (less than 10 minutes) without additional personnel. This had a substantial impact on the clinician's ability to diagnose acute myocardial infarction and to move patients out of an intensive care unit at substantial financial savings to the patient, the hospital, or the third-party payer. Second, the Stratus assay was able to detect low levels of CK-MB (1 to 2 micrograms/L) in the presence of low total creatine kinase activity (less than 100 U/L). Third, the Stratus assay showed no interference due to very-high-total creatine kinase activities (greater than 100,000 U/L), CK-BB, macro-creatine kinase, and mitochondrial creatine kinase. 