Creatine kinase activity in the detection of carriers of Duchenne muscular dystrophy: comparison of two methods.

ABSTRACT

Serum creatine kinase activity was estimated in 48 control women and 22 female carriers of Duchenne muscular dystrophy by two different methods. One method is based on the colorimetric determination of creatine liberated from creatine phosphate; the other, an N-acetyl cysteine activated UV system, was used in an automated mode. The two methods were equally efficient in carrier detection, and results were closely correlated over the range of values encountered in controls and carriers. Log creatine kinase values appeared to be normally distributed in controls, but the distribution in carriers appeared skewed towards its upper end. If both distributions are assumed to be Normal, the probability, together with its standard error, that a consultand is a carrier, can be calculated from her creatine kinase value, and if the latter is expressed in standard deviation units of the control log creatine kinase distribution, probability estimates can be compared between laboratories.