Automafed FluorometricCreatine KinaseAssay. Measurement of 100-Fold NormalActivitywithoutSerum Dilution

Creatine kinase (EC 2.7.3.2) activity can be measured fluorometrically by coupling the reaction product, creatine, to ninhydrin at alkaline pH. We have automated this procedure to develop an accurate and precise method, which requires 0.1 ml of sample and can be performed at 60 tests per hour. By using an abbreviated incubation time and a dia!yzer in the iiay, we have extended the analytical range to 100 times normal serum activity without sample dilution. The dialyzer also eliminates the nonspecific protein fluorescence of the sample. An additional advantage of the method is the reduced cost of reagents In comparison to similar procedures. Serum blanks should be analyzed whenever serum creatine is abnormally high, especially In cases of severe renal failure.