Creatine kinase reference intervals determined from a multi-centre data pool.

Reference intervals for creatine kinase assayed at 37 degrees C using N-acetyl cysteine-activated methods have been determined on data obtained from 10 laboratories throughout Australia. The pooled distributions for males and females are skewed towards higher values and cannot be transformed to Gaussian distributions. The reference interval for females was calculated to be 34 to 180 U/l and for males it was 46 to 300 U/l. However, if creatine kinase is to be used in the diagnosis of myocardial infarction, the upper limit of the reference interval for males is considered to be too high. It is concluded that for males, the upper limit may need to be determined on specific populations such as hospital inpatients.