A Comparison of Four Methods for Measuring Creatine Phosphokinase

Abstract

Four commercially available methods for measuring creatine phosphokinase were compared. All four methods can be used successfully and all provide clinically useful information. The ultraviolet spectrophotometric method demonstrated the greatest precision with serum specimens having normal or moderate elevations of CPK activity. Greater and more prolonged elevations of CPK activity were demonstrated by the spectrophotometric method than by the colorimetric methods. The colorimetric methods studied were less precise, particularly at lower levels of enzymic activity, and did not permit a sharp distinction between normal and slightly elevated levels of enzymic activity. These procedures were also less sensitive since they produced more false-negative results. However, colorimetric methods appear more adaptable to automated analysis than the spectrophotometric procedure.