Radioimmunoassay for MM and BB isoenzymes of creatine kinase substantiated by clinical application.

We have developed a radioimmunoassay technique that is highly specific for measuring the MM isoenzyme of creatine kinase. The specificity of the radioimmunoassay for the BB isoenzyme was poor. In patients with treated Duchenne-type muscular dystrophy or untreated hypothyroidism, the MM isoenzyme, but not the BB isoenzyme value, was consistently above above normal. In the radioimmunoassay for the BB isoenzyme the antisera might cross react with other materials and the inactivated isoenzyme, but not with MM or MB isoenzymes.