Evaluation of 21-numbered circle and 10-centimeter horizontal line visual analog scales for physician and parent subjective ratings in juvenile idiopathic arthritis.

OBJECTIVE: 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). METHODS: 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). RESULTS: 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. CONCLUSION: 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.