Steroid-CPK test. A new diagnostic aid for muscular dystrophy and its carriers?

The response of serum creatine phosphokinase (SCPK) to intravenous hydrocortisone was studied in different neuromuscular diseases, in Duchenne carriers and relatives of various muscular dystrophy (MD) cases. SCPK activity increased significantly in MD cases, 50% of known and 18.7% of possible Duchenne carriers. No such increase was found in other neuromuscular disease, in other relatives of MD cases and in normal controls. An inverse correlation was observed between the grade of disability and post-steroid percentage increase of SCPK activity in X-linked severe (DMD) cases. Such an inverse correlation was also found between the duration of the disease and post-steroid percentage increase of SCPK activity in DMD cases. A possible explanation is given.