Distribution of serum creatine kinase activity in young healthy persons

The normal distribution of serum creatine kinase (CK) was determined in 428 men (mean age = 21.5) and 540 women (mean age = 20.2). The bootstrap metho d was employed to obtain statistical parameters of CK reference range and c orrelations with physical activity habits, BMI, cigarette smoking and alcoh ol consumption. CK distribution was non-Gaussian and skewed toward the high er values; 18.9% of the men and 3.6% of the women had values above the uppe r reference limits defined for the commercial assay kit. The median 97.5 pe rcentile value was 532 u/l for men and 248 u/l for women (95% confidence in terval of 384-738 u/l and 184-340 u/l, respectively). A significant correla tion was found only between CK and alcohol consumption in men. Myoglobin le vel in a representative group of subjects correlated well with CK activity for both genders. Our findings define the range of CK values in a healthy, young, heterogeneous population. We suggest that only CK levels above the d etermined 97.5 percentile should warrant further clinical investigation. (C ) 1999 Elsevier Science B.V. All rights reserved.