Macromolecular creatine kinase type 1: a serum marker associated with disease.

The prevalence of circulating macromolecular creatine kinase type 1 (macro CK type 1 or CK-immunoglobulin complexes) is significantly higher in a patient population selected for CK isoenzyme assay than in age- and sex-matched blood donors (n = 1304). In greater than 8000 patients studied, 49 individuals with macro CK type 1 were identified, yielding an overall prevalence of 0.61%. Macro CK type 1 complexes occurred more frequently in women and in patients older than 70 years, and were often associated with complications of cardiovascular disease, life-threatening conditions, and poor outcome. These latter clinical associations could arise, at least partly, from the selection of patients for whom CK isoenzyme analysis was ordered.