Abstract
Objective To evaluate the validity of the 3-item visual analog scale (3VAS) and 4-item VAS (4VAS) and determine the minimal clinically important difference (MCID) and minimal detectable change (MDC) for each measure using data from 3 phase III randomized clinical trials of guselkumab in psoriatic arthritis (PsA).
Methods Pooled data (1405 participants) from the DISCOVER-1, DISCOVER-2, and COSMOS studies were used. 3VAS/4VAS MCID and MDC were estimated using established formulas. Receiver-operating characteristic curve analysis was used to identify 3VAS/4VAS thresholds for low, moderate, and high disease activity. Criterion validity was assessed by correlating 3VAS/4VAS with other PsA measures. Mixed models evaluated the association between changes from baseline in 3VAS/4VAS at week 8 of guselkumab treatment with the total PsA-modified Sharp-van der Heijde (SvdH) score through week 100.
Results 3VAS/4VAS showed moderate-to-strong correlation with all outcome measures assessed, with coefficients ranging from 0.56/0.62 for Health Assessment Questionnaire–Disability Index to 0.92/0.94 for patient global assessment. MCID was 0.9 for both 3VAS (range 0.7-1.3 depending on method used) and 4VAS (0.6-1.3); MDC was 3.1 and 3.0, respectively. 3VAS cutoffs for low, moderate, and high disease activity were 2.1, 3.3, and 4.8, respectively, and 2.1, 3.4, and 5.0 for 4VAS. Change in 4VAS at week 8 of guselkumab treatment significantly associated with change in SvdH score through week 100 (P = 0.04).
Conclusion These analyses support the validity of 3VAS/4VAS as multidimensional measures of PsA disease activity. 4VAS may be preferred owing to its greater face validity and separate measurements of the 2 cardinal aspects of PsA (joint/skin disease) and pain.
Plain Language Summary
Feasibility is a significant barrier to psoriatic arthritis (PsA) disease assessment and implementation of the treat-to-target strategy in clinical practice. The 3-item visual analog scale (3VAS) and the 4-item VAS (4VAS) are the first short multidimensional composite measures that can be completed rapidly within routine clinical care, with evidence supporting their superior performance in small datasets.
Using a large clinical trial dataset, this analysis assessed the criterion validity of the 3VAS and 4VAS and estimated thresholds of meaningful improvement in these measures.
Based on pooled results of 1405 participants with moderate-to-severe PsA treated with guselkumab in 3 phase III studies, 3VAS and 4VAS were highly correlated with other commonly used PsA measures, providing evidence for their criterion validity. The 3VAS and 4VAS thresholds for minimal clinically important difference and minimal detectable change, as well as estimated cutoffs for low, moderate, and severe disease activity were comparable with those reported previously. Early changes in 3VAS and 4VAS with guselkumab treatment were associated with long-term changes in radiographic progression.
These findings demonstrate that the 3VAS and 4VAS are feasible, patient-centered, multidimensional instruments for the assessment of PsA in routine care and the implementation of a treat-to-target strategy. The 4VAS may be the preferred measure owing to its greater face validity and clinical utility in daily practice. In addition to the physician global assessment, the 4VAS includes separate assessments for the two cardinal aspects of PsA, joint and skin disease, as well as pain, the outcome ranked as highest priority by patients with PsA.
