Chapter 7 176 Statistical analysis Data were analysed using Statistical Packages for Social Sciences (SPSS, Chicago, II, USA, version 28.0). Descriptive methods were used to assess quality of data, homogeneity of treatment groups and endpoints. Normality of the data were analysed with histograms. Data are presented using mean (SD), median (min-max) for the numeric and non-normal variables and frequency (percentages) for categorical variables. A paired t-test or Wilcoxon signed-rank test was used to compare continuous variables within groups. An independent t-test or Mann- Whitney U test for quantitative data was performed to analyse statistical differences between groups. For each of the dimensions of the RAND-36, items scores were coded, summed, and transformed on to a scale of 0 to 100. Statistical analyses consisted of estimating means and standard deviations for each of the RAND-36 scale scores. Comparison between groups for continuous variables was made by repeated measure analysis of variance using a mixed model after transformation of the data to enhance normality, with treatment, time (categorical) and their interaction as fixed effects and with random patient effects. To acquire an indication of the QoL of life of patients with CAF as compared to the reference group of the Dutch population, we calculated for each dimension the significance from the norm score13 with the one-sample t-test. In case of missing data, we excluded that specific case in total from further analyses when less than 75% of the questionnaire was filled out. All p values were two-tailed, and statistical significance were taken as a p value of less than 0.05. Results Between December 2018 and July 2021, 140 patients, were randomized to PFPT or postponed PFPT. After randomisation, 3 patients withdrew. The RAND-36 was adequately completed by 100 patients at baseline, of whom 50 women and 50 men with a mean age of 44.6±11.1 (range 19-68). The results from the questionnaires at baseline of 37 patients were excluded because less than 75% of the form had been completed. The participants’ demographic and clinical characteristics of the total group of patients from the PAF-study, those who completed the baseline questionnaire adequately and individual treatment groups, are presented in Table 1. There were no significant differences in terms of demographic or clinical parameters between the groups at baseline (Table 1).
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