Automated enzymatic determination of serum and urine creatine using the Abbott ABA-200

A new enzymatic method is described for the determination of creatine in serum and urine with Abbott ABA-200. The measurement is accomplished by transforming creatine to formic acid in a reaction catalyzed by creatinase (creatine amidinohydrolase), sarcosine oxidase and formaldehyde dehydrogenase (see Figure 1). The assay takes less than 20 minutes. The standard response is linear for creatine concentrations up to 10 mg/dL (serum) and 80 mg/dL (urine). The coefficients of variation at 0.69 mg/dL (serum) and 4.93 mg/dL (urine) for within-day determination were less than 4% and, for between-day determination, were less than 5%. Results obtained by this procedure on one hundred serum and urine samples conformed well with a manual enzymatic method and the Folin method. The method is useful for the automated measurement of creatine in serum and urine.