Researchers' choice of pain scales in trials of children undergoing surgery: A cross-sectional analysis of systematically searched randomized controlled trials and survey of authors

Background Many pain scales are used post-operatively in pediatric trials, making the comparison of trials, and the pooling of data for meta-analyses difficult. The Pediatric Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (PedIMMPACT) statement, published in 2008, attempted to address this issue. We aimed to investigate the reasons for authors' choice of pain scales and the potential impact of PedIMMPACT. Methods We performed a cross-sectional analysis of systematically searched randomized controlled trials testing tramadol in children (up to 16 years) undergoing surgery, published between 2000 and 2020 (9 years prior to and 12 years following the publication of PedIMMPACT). Results Among 76 trials (6211 children), 49 unique pain scales were used. The choice of the scales was explained in 18 trials (24%); in 13 of them, authors at least partly justified their choice by the fact that the pain scale was validated. In 52 trials (68%), the pain scales were referenced, with a total of 59 unique references, most often to prior studies using the same scale (36%) or to studies validating the chosen scale (31%). Twenty-three trials (30%) provided no explanation nor reference. One single trial referenced PedIMMPACT. There was no evidence of a change in the choice of pain scales after the publication of PedIMMPACT. Conclusions A large variety of pain scales are still used in pediatric post-operative pain trials 12 years after the publication of PedIMMPACT. Only a minority of trials provided an explanation for their choice of pain scale. The reasons given most often included that the scale was validated or it was justified by a reference to a prior study using that scale. The impact of the publication of the PedIMMPACT seems limited. The ethics of the ongoing usage of large numbers of pain scales in pediatric pain trials must be challenged.