Determining the minimum clinically significant difference in visual analog pain score for children

Study Objective: We sought to determine the minimum clinically significant difference in visual analog scale (VAS) pain score for children. Methods: We performed a prospective, single-group, repeated-measures study of children between 8 and 15 years presenting to an urban pediatric emergency department with acute pain. On presentation to the ED, patients marked the level of their pain on a 100-mm nonhatched VAS scale. At 20-minute intervals thereafter, they were asked to give a verbal categoric rating of their pain as “heaps better,” “a bit better,” “much the same,” “a bit worse,” or “heaps worse” and to mark the level of pain on a VAS scale of the same type as used previously. A maximum of 3 comparisons was recorded for each child. The minimum clinically significant difference in VAS pain score was defined as the mean difference between current and preceding scores when the subject reported “a bit worse” or “a bit better” pain. Results: Seventy-three children were enrolled in the study, yielding 103 evaluable comparisons in which pain was rated as “a bit better” or “a bit worse.” The minimum clinically significant difference in VAS score was 10 mm (95% confidence interval 7 to 12 mm). Conclusion: This study found the minimum clinically significant difference in VAS pain score for children aged 8 to 15 years (on a 100-mm VAS scale) to be 10 mm (95% confidence interval 7 to 12 mm). In studies of populations, differences of less than this amount, even if statistically significant, are unlikely to be of clinical significance. [Powell CV, Kelly A-M, Williams A. Determining the minimum clinically significant difference in visual analog pain score for children. Ann Emerg Med. January 2001;37:28-31.]