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Chapter 3 54 which data were not available and were therefore not included in the analysis of the current study. Statistical analysis All statistical analyses were carried out using IBM SPSS statistics 23.0 (Chicago IL, USA) and GraphPad Prism 6.0 (La Jolla, CA, USA) for Macintosh. Continuous data are presented as medians and interquartile ranges (IQR) and categorical data as proportions (%). To compare (non-parametric) continuous data between subgroups, Mann-Whitney U tests were used. Wilcoxon-signed-rank tests were used to evaluate differences within subjects over time. For categorical data, groups were compared using the Chi-square or Fisher’s exact test and differences over time were evaluated using the McNemar’s test. Correlations were assessed according to Spearman. To decrease the false discovery error rate induced by multiple testing, a post-hoc correction was applied using the Benjamini-Hochberg step-up procedure. 32 The patients participating in the follow-up were divided into two groups for comparison and further analyses, 1) Rome III-positive: patients who still fulfilled the Rome III criteria for IBS at follow-up; 2) Rome III-negative: patients who did not fulfill the Rome III criteria for IBS at follow-up. Multivariable logistic and linear regression models, respectively, were used to identify independent baseline predictors for 1) the presence of IBS according to the Rome III diagnostic criteria at follow-up; 2) quality of life at follow-up. We also used linear regression models to identify characteristics at follow-up that were associated with quality of life at follow-up. The of the linear regression analyses signifies one-point change in the mental or physical quality of life component summary. Results Study population for follow-up of the Rome III irritable bowel syndrome cohort At a mean follow-up time of 4.7 (SD 1.5) years, 379 patients with IBS, Rome III-positive at inclusion and participating at least three (five +/- two) years in the Maastricht IBS cohort, were approached for participation in the follow-up measurement. A total of 203 subjects (53.7%) responded by completing the electronic or paper questionnaires. Of these, 161 could be reached by telephone to confirm the Rome criteria, and these did not differ in demographics nor in symptom scores when compared to the 42 subjects that were not reached. A study flowchart is shown in Figure 3.1 .