Els van Meijel

67 Results of a 2–4-year follow-up study | Chapter 4 PTSD The second part of the interview consisted of the PTSD module of the ADIS-C/P (see the previous subsection “Posttraumatic stress disorder”). Figure 4.1 provides an overview of measures used at the different time points. Statistical analysis Answers to questions on permanent physical impairment, psychosocial consequences and new traumatic events were classified by the first author and confirmed by the second author. Differences were discussed until consensus was reached. According to the definitions (see “Measures, health and mental health…”), answers were coded dichotomously: present ‘yes’ or ‘no’. Thereafter we quantified the answers. The frequencies were used to compare the groups with and without PTSD or PTSS. Information on trauma-focused treatment between T1 and T2 was described in relation with PTSD or PTSS outcome at T2. Differences between follow-up participants and non-participants were analyzed with Mann–Whitney U tests for age and posttraumatic stress at the time of the first assessment, and a Fisher’s exact test for sex. The statistical significance of differences between children with and without PTSDwas determined with Mann–Whitney U tests for the mean acute pain scores and the number of traumatic events until follow-up and with Fisher’s exact test for the other items: the number of children (1) with trauma history before the accident (2) that experienced a new traumatic event between T1 and T2 (3) that reported severe acute pain and (4) with permanent physical impairment. Statistical significance was set at an alpha level of 0.05. Confidence intervals were calculated with Confidence Interval Analysis (Bryant, 2018). Other statistical analyses were performed using SPSS 24 (IBM Statistical Product and Service Solutions, Chicago, IL).