["The COMFORT behaviour scale (COMFORT-B scale) is widely used in paediatric intensive care units to assess young children's pain and distress. It is also used to assess the impact of treatment interventions, but little is known on the scale's sensitivity to detect changes between before and after measurements following an intervention. This study explored the sensitivity to change of the COMFORT-B scale.", 'COMFORT-B scores, originally and prospectively collected as part of standard care, were retrieved from the digital patient data management system. We analysed scores obtained in 747 paired observations, i.e., before and after a pharmacological intervention in 180 paediatric intensive care patients between September 2009 and September 2010.', 'The mean scores before and after an intervention were 20.0 [standard deviation (SD) 3.7] and 14.1 (SD 4.7), respectively. Multilevel regression analysis showed a 6-point mean decline after an intervention (p\u2009<\u20090.0001). The magnitude of this decline was not statistically significantly related to number and type of interventions or time between assessments. In almost three-quarters of cases (74%), the COMFORT-B score dropped to below 17 after a pharmacological intervention, indicating good responsiveness.'] Does the COMFORT behaviour scale detect clinically meaningful effects of analgesic and sedative treatment?