Creatine kinase in a biochemical test panel: the high cost of a seemingly inexpensive test.

Analysis of cost-effectiveness of a laboratory test requires not only calculating the cost of doing the test in the laboratory, but also determining the clinical effectiveness of the data produced. In this hospital, creatine kinase (CK) is available only as part of a 19-test panel. The cost per CK result was $0.64, based on cost of material and labor used exclusively for CK. To evaluate the yield from CK as a screening test, 252 patients were investigated with CK greater than 200 U/l on a biochemical panel within 24 hours of admission. The authors found no instance of a new diagnosis established because of the initially elevated CK. To complete the analysis of cost-effectiveness, the authors estimated the daily workload for CK tests needed for diagnostic purposes. Of the 600 CK tests done daily as part of biochemical panels, no more than 40 were clinically necessary. The true cost for a useful CK test was $9.60--15 times higher than the apparent cost of $0.64.