Venous creatinine as a biomarker for loss of fat-free mass and disease progression in patients with amyotrophic lateral sclerosis

To establish the utility of venous creatinine as a biomarker to monitor loss of fat-free mass in patients with amyotrophic lateral sclerosis (ALS).In this multicenter natural history study, body composition and venous creatinine were assessed in 107 patients with ALS and 52 healthy controls. Longitudinal patterns of venous creatinine and its association with the risk of death during follow-up were determined in a cohort of patients with ALS from Australia (n = 69) and the Netherlands (n = 38).The mean levels of venous creatinine were 75.78 ± 11.15 μmol/L for controls, 70.25 ± 12.81 μmol/L for Australian patients, and 59.95 ± 14.62 μmol/L for Dutch patients with ALS. The relationship between measures of venous creatinine and fat-free mass was similar between all groups (r = 0.36, p 0.001). Within patients, fat-free mass declined by 0.31 (95% confidence interval [CI]: 0.22-0.40) kg/month, and venous creatinine declined by 0.52 (95% CI: 0.38-0.66) μmol/L/month, with a longitudinal correlation of 0.57 (95% CI: 0.35-0.76, p 0.001). Lower levels of venous creatinine were associated with increased risk for earlier death in patients with ALS (hazard ratio = 0.94, 95% CI: 0.90-0.98, p = 0.007).Venous creatinine is decreased in ALS and declines alongside a decline in fat-free mass over the course of the disease, and may serve as a practical marker to monitor the change of fat-free mass in patients with ALS. This could inform clinical care and provide an alternative endpoint for the evaluation of therapeutic interventions that focus on slowing the loss of fat-free mass and disease progression in ALS.