Sample size
The sample size calculation was based on the study by Unsgaard-Tøndel et al. [Accepting an alpha risk of 0.05 (95% confidence) and a beta risk of 0.1 (statistical power of 90%), using a two-sided contrast, 17 individuals were necessary in each group (34 patients in total), accepting a patient drop-out rate of 20%. We used the sample-size calculator GRANMO version 7.12.A simple random sampling method without replacement was used to ensure a representative sample of our target population.