Correlation of Serum Creatine Kinase Level With Pulmonary Function in Duchenne Muscular Dystrophy

OBJECTIVE To investigate the relationship between serum creatine kinase (CK) level and pulmonary function in Duchenne muscular dystrophy (DMD). METHODS A total of 202 patients with DMD admitted to the Department of Rehabilitation Medicine, Gangnam Severance Hospital were enrolled from January 1, 1999 to March 31, 2015. Seventeen patients were excluded. Data collected from the 185 patients included age, height, weight, body mass index, pulmonary function tests including forced vital capacity (FVC), peak cough flow, maximal expiratory pressure (MEP), and maximal inspiratory pressure (MIP), and laboratory measurements (serum level of CK, CK-MB, troponin-T, and B-type natriuretic peptide). FVC, MEP, and MIP were expressed as percentages of predicted normal values. RESULTS Serum CK activities were elevated above normal levels, even in the oldest DMD group. Serum CK level was strongly correlated with pulmonary functions of sitting FVC (p<0.001), supine FVC (p<0.001), MIP (p=0.004), and MEP (p<0.001). CONCLUSION Serum CK level is a reliable screening test even in patients with advanced DMD, and is a strong predictor of pulmonary functions.