Psychometric comparison of three behavioural scales for the assessment of pain in critically ill patients unable to self-report

Introduction: Pain assessment is associated with important outcomes in ICU patients but remains challenging, particularly in non-communicative patients. Use of a reliable tool is paramount to allow any implementation of sedation/analgesia protocols in a multidisciplinary team. This study compared psychometric properties (inter-rater agreement primarily; validity, responsiveness and feasibility secondarily) of three pain scales: Behavioural Pain Scale (BPS/BPS-NI, that is BPS for Non-Intubated patients), Critical Care Pain Observation Tool (CPOT) and Non-verbal Pain Scale (NVPS), the pain tool routinely used in this 16-bed medical ICU. Methods: Pain was assessed by at least one of four investigators and one of the 20 bedside nurses before, during and 10 minutes after routine care procedures in non-comatose patients (Richmond Agitation Sedation Scale >= - 3) who were unable to self-report their pain intensity. The Confusion Assessment Method for the ICU was used to assess delirium. Non-parametric tests were used for statistical analysis. Quantitative data are presented as median (25(th) to 75(th)). Results: A total of 258 paired assessments of pain were performed in 30 patients (43% lightly sedated, 57% with delirium, 63% mechanically ventilated). All three scales demonstrated good psychometric properties. However, BPS and CPOT exhibited the best inter-rater reliability (weighted-kappa 0.81 for BPS and CPOT) and the best internal consistency (Cronbach-alpha 0.80 for BPS, 0.81 for CPOT), which were higher than for NVPS (weighted-kappa 0.71, P <0.05; Cronbach-alpha 0.76, P <0.01). Responsiveness was significantly higher for BPS compared to CPOT and for CPOT compared to NVPS. For feasibility, BPS was rated as the easiest scale to remember but there was no significant difference in regards to users' preference. Conclusions: BPS and CPOT demonstrate similar psychometric properties in non-communicative intubated and non-intubated ICU patients.