Cut points for mild, moderate, and severe pain on the VAS for children and adolescents: what can be learned from 10 million ANOVAs?

Cut points that classify pain intensity into mild, moderate, and severe levels are widely used in pain research and clinical practice. At present, there are no agreed-upon cut points for the visual analog scale (VAS) in pediatric samples. We applied a method based on Serlin and colleagues' procedure (Serlin RC, Mendoza TR, Nakamura Y, Edwards KR, Cleeland CS. When is cancer pain mild, moderate or severe? Grading pain severity by its interference with function. PAIN(®) 1995;61:277-84) that was previously only used for the 0 to 10 numerical rating scale to empirically establish optimal cut points (OCs) for the VAS and used bootstrapping to estimate the variability of these thresholds. We analyzed data from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) study and defined OCs both for parental ratings of their children's pain and adolescents' self-ratings of pain intensity. Data from 2276 children (3 to 10 years; 54% female) and 2982 adolescents (11 to 17 years; 61% female) were analyzed. OCs were determined in a by-millimeter analysis that tested all possible 4851 OC combinations, and a truncated analysis were OCs were spaced 5 mm apart, resulting in 171 OC combinations. The OC method identified 2 different OCs for parental ratings and self-report, both in the by-millimeter and truncated analyses. When we estimated the variability of the by-millimeter analysis, we found that the specific OCs were only found in 11% of the samples. The truncated analysis revealed, however, that cut points of 35:60 are identified as optimal in both samples and are a viable alternative to separate cut points. We found a set of cut points that can be used both parental ratings of their children's pain and self-reports for adolescents. Adopting these cut points greatly enhances the comparability of trials. We call for more systematic assessment of diagnostic procedures in pain research.