Correlation of Creatine Kinase Levels with Clinical Features and Survival in Amyotrophic Lateral Sclerosis

Objective: To evaluate serum creatine kinase (CK) levels of amyotrophic lateral sclerosis (ALS) patients and to explore the relationship between CK levels and the clinical characteristics and survival prognosis of ALS patients. Methods: We analyzed the CK levels of 185 ALS patients who underwent long-term follow-up. The relationship between CK levels and clinical features including sex, age, disease duration, site of onset, body mass index (BMI), serum creatinine (Cr), and spontaneous electromyographic activity was analyzed by univariate analysis and multiple linear regression. Kaplan-Meier and Cox proportional hazards models were used to explore whether CK levels were independently correlated with survival prognosis of ALS. Results: Baseline serum CK was raised in 43% of participants. The median CK level was 160 U/L (range: 20-2,574 U/L), and 99% of patients had a baseline serum CK level less than 1,000 U/L. CK levels were significantly higher in male patients than in female patients [204 (169) versus 117 (111) U/L, p < 0.001] and in patients with limb onset ALS than with bulbar onset ALS (p < 0.001). CK levels were also correlated with serum Cr (p = 0.011) and the spontaneous potential score of electromyography (EMG) (p = 0.037) but not correlated with age (p = 0.883), disease duration (p = 0.116), or BMI (p = 0.481). Log CK was independently correlated with survival of ALS patients (HR = 0.457, 95% confidence interval 0.221-0.947, p = 0.035) after adjusting for age, sex, site of onset, serum Cr, and BMI. Conclusion: Serum CK levels of ALS patients were correlated with sex, site of onsite, serum Cr, and spontaneous activity in EMG. Serum CK could be an independent prognostic factor for survival of ALS patients.