To evaluate the measurement properties of 21-numbered circle visual analog scales (VAS) and traditional 10-cm horizontal line VAS for physician and parent subjective ratings in children with juvenile idiopathic arthritis (JIA).
We studied 2 patient samples in whom physician global rating of overall disease activity, parent global rating of the child's overall well-being, and parent rating of intensity of child's pain were performed using traditional 10-cm horizontal line VAS (n = 397) or 21-numbered circle VAS (n = 471). The measurement performances of the 2 VAS formats were examined by assessing construct validity, score distribution, responsiveness to change over time, and minimal clinically important difference (MCID).
Most Spearman correlations with other JIA outcome measures yielded by 21-numbered circle VAS were greater than those obtained with 10-cm horizontal line VAS, revealing that the circle VAS format has better construct validity. Ceiling effects (i.e., score = 0) for physician and parent global ratings were 43.7% and 32.9%, respectively, on 21-numbered circle VAS, and 31.6% and 35.3%, respectively, on 10-cm horizontal line VAS. Responsiveness of 21-numbered circle VAS was good (standardized response mean > 0.8) or moderate (standardized response mean > 0.6) among patients classified as improved or worsened, respectively, by the physician or the parent. Overall, MCID values for 21-numbered circle VAS tended to be greater for worsening than for improvement.
The 21-numbered circle VAS are a suitable alternative to the 10-cm horizontal line VAS and may facilitate incorporation of physician and parent subjective ratings in standard clinical practice.