Els van Meijel

45 Acute pain and posttraumatic stress symptoms | Chapter 3 The cut-off score for a positive test is 30. The outcome correlates highly with the PTSD diagnosis according to the Anxiety Disorders Interview Schedule for DSM-IV, Child and Parent Version (ADIS C/P) (Verlinden et al., 2014). For the current sample Cronbach’s alpha was .87 (van Meijel et al., 2015). Clinical information Information on the presence of an extremity fracture and the length of hospitalization was obtained from the medical records, including the ambulance and Emergency Departments reports. The Injury Severity Score (ISS) was obtained from the trauma registry. In the trauma registry, part of a national trauma registry system, trained data managers register prehospital, in-hospital and discharge data on injury mechanism, vital signs, type and severity of injuries, treatment and outcome. The purpose of the national registry system is to be able to evaluate and improve quality of trauma care in the Netherlands. The ISS is a method for describing the severity of injuries in trauma patients. It is related to the likelihood of survival after injury. The ISS is determined by rating the severity of each injury in six body regions (head, neck, face, chest, abdomen, extremity and external) on the six-point Abbreviated Injury Scale (AIS). The AIS score per body region has a range of 1 ( minor injury ) to 6 ( unsurvivable injury ). The ISS is derived from the sum of the squares of the AIS score of the three most severely injured body regions and has a range of 0–75 (i.e., 5 2 +5 2 +5 2 ). If an injury is assigned an AIS of 6 ( unsurvivable injury ), the ISS score is automatically set to 75. Injury severity can be divided into six categories: minor (1–8), moderate (9–15), serious (16–24), severe (25–49), critical (50–74) and maximum (75) (Baker et al., 1974; Saxe et al., 2005). Statistical analyses The datawe have presented here originated froma previous study (vanMeijel et al., 2015) that aimed to validate the STEPP using responses from150 participants. This sample size was based on three assumptions: that there would be a prevalence of PTSD of 25%, that the STEPP would have a sensitivity of 90% to identify children at risk for PTSD, and that a 95% confidence interval with limits of 75% and 97% for the sensitivity was required. A total of 161 participants were included. As this paper describes a convenience sample from the earlier STEPP study, no formal power analysis was performed for the current study. However, a post-hoc power analysis assuming one sample and a correlation of .3 showed that a sample of 135 patients is sufficient to estimate the correlation coefficient