Els van Meijel

46 Chapter 3 | Acute pain and posttraumatic stress symptoms and associated 95% confidence interval with a lower bound of 0.14 and an upper bound of 0.45 (nQuery Advisor Version 7.0, Statsols, Cork, Ireland). We used descriptive statistics to summarize demographic and clinical information on the participants. The differences between boys and girls were tested with Mann– Whitney U test for age, injury severity, worst pain, length of hospitalization, and severity of PTSS (total score CRIES) at 3 months, and with Fisher’s exact test for the presence of an extremity fracture. In addition, we calculated effect sizes using Cohen’s d . We examined whether variables followed a normal distribution by visually inspecting histograms. As the pain and CRIES scores clearly did not follow normal distributions, we used Spearman’s rho correlation coefficient to present the associations between variables. The following variables were included in the analyses: gender (as a fixed variable before the accident), the presence of an extremity fracture, the injury severity, the worst experienced pain, the length of hospitalization, and the total score of self-reported PTSS at 3 months (variables ordered in time from the moment of the accident). Correlation coefficients can be interpreted as .0 to (–).3 = negligible ; (–).3 to (–).5 = low ; (–).5 to (–).7 = moderate ; (–).7 to (–).9 = high ; (–).9 to –(1) = very high (Hinkle, Wiersma, & Jurs, 2003). A p value of less than .05 was considered statistically significant. Analyses were performed using SPSS 24 (IBM Statistical Product and Service Solutions, Chicago, IL). Results Sample characteristics Table 3.1 summarizes the sample characteristics for the total group of 135 children included in this study, and for boys and girls separately, and shows the differences and effect sizes between both groups on all variables. We found no significant differences between boys and girls, except on the severity of posttraumatic stress: girls had a higher CRIES score than boys. In total 94 children (70%) were hospitalized. ISS’s were available for 134 children. Injury severity was classified as zero for 31 children (23%), minor for 58 children (43%), moderate for 28 children (21%), serious for 12 children (9%) and severe for 5 children (4%). The number of days between the accident and the first assessment was not associated with the amount of pain ( r s = .04; p = .62) nor with the severity of PTSS ( r s = .04; p = .68).