WS21.5 The use of serum creatinine to estimate skeletal muscle mass in cystic fibrosis

Objectives A lack of skeletal muscle mass is associated with an increase in mortality amongst people with cystic fibrosis (CF). Serum creatinine can be used as a surrogate marker of muscle mass in people with normal renal function and under steady state conditions. The aim of the current study was to investigate the feasibility of using creatinine to estimate muscle mass in CF patients with normal renal function and examine the potential impact of physical activity status. Methods The body composition of seventeen patients was assessed using leg-to-leg bioelectrical impedance. Physical activity status was estimated using the Global-Physical-Activity-Questionnaire. The Pearson correlation coefficient (r) was used to determine the strength of relationships between measures of body composition, levels of creatinine and physical activity status. Results Mean (±SD) body mass, muscle mass and body fat was reported at 63.8±13.7 kg, 48.3±9.0 kg and 19.5±9.4% respectively. Muscle mass showed a strong and positive correlation to creatinine (r = 0.81, p Conclusion Creatinine is a good indicator of skeletal muscle mass in patients with CF and represents a useful biomarker in the assessment of nutritional status. Patients who present with low creatinine may be attributed to a depletion in the relative proportion of muscle mass. The amount of time spent being sedentary each week seems, to a greater degree, determine skeletal muscle mass.