Validation of a six-graded faces scale for evaluation of postoperative pain in children

Background. The faces pain scales are often used for self-report assessment of paediatric pain. The aim of this study was to evaluate the validity of a six-graded faces pain scale after surgery by comparing the level of agreement between the children's report of faces pain scores and experienced nurses' assessment of pain by observation of behaviour. The faces pain scores before, at and after administration of analgesics were analysed. The study was performed in two South African hospitals, one with a mainly rural population and the other with an urban population. Methods. A total of 110 children aged 4-12 years, scheduled for inguinal surgery in the two South African hospitals, were included in the study. The anaesthetic technique was standardized. All patients received a caudal block preoperatively. Postoperative pain assessments were made every hour for 8 h after the caudal block was performed. A designated nurse assessed pain by using a four-graded descriptive scale (no, mild, moderate or severe pain) and thereafter the child reported pain by using the six-graded faces pain scale. Results. A high correlation was found between the two methods of assessment (tau = 0.76, P < 0.0001). The correlation between methods was high in both hospital populations and in all age groups. The weakest correlation was found in children aged 8-12 years (tau = 0.56, P < 0.01). Significantly lower faces pain scores were found after administration of analgesics compared with pain rating before analgesics (P < 0.0001). The proportion of patients with pain scores above 2 decreased from 86% to 31% (P < 0.001). Conclusions. The findings support this six-graded faces pain scale as a useful and valid instrument for measuring pain in the postoperative period in children aged 4-12 years.