Black-white differences in serum creatine phosphokinase (CPK) activity

The mean serum creatine phosphokinase activities of hospitalized black male and female, and white male and female psychiatric patients were established. The effects of both race and sex on mean serum creatine phosphokinase activities were both highly significant. Black males had significantly higher mean serum creatine phosphokinase activity than white males, black females and white females. White males and black females had significantly higher mean serum creatine phosphokinase levels than white females but were not significantly different from each other. Age, height and weight did not contribute to the difference between races. There was a trend for mean serum creatine phosphokinase activity to be greater for dark skinned black males than light skinned black males but this trend was not present in black females. The standard deviation of each subject's mean serum creatine phosphokinase activity was highly correlated with the mean. The levels of serum creatine phosphokinase activity found in these subjects were significantly greater than those previously observed with the method of Rosalki (J. Lab. Clin. Med., 69 (1967) 696).