Sample size and reliability analysis
The power sample analysis, calculated using statistical software (G* POWER, Universität Düsseldorf, Germany), was obtained by setting up serum GDF-15 as a primary outcome variable [An inter-examiner reliability test among examiners (S.S., A.L.G.) was performed using Cohen’s kappa coefficient and showed an agreement of 85.8% (k = 0.63) for the primary outcome chosen, CAL, indicating a high degree of reliability. The kappa coefficient was also calculated for the measurements taken at each follow-up session, and an acceptable degree of reliability was established for every examination (intra-class correlation coefficient, ICC = 0.770).