Construct Validity of the Routine Assessment of Patient Index Data 3 (RAPID3) in the Evaluation of Axial Spondyloarthritis

. Objective. Although there are different tools to evaluate axial spondyloarthritis (axSpA), they are hardly used in routine clinical practice due to time constraints. The Routine Assessment of Patient Index Data 3 (RAPID3) is a composite measure feasible for use as a sole metric in busy clinics. We aimed to test its measurement properties in patients with axial SpA in a real-world clinical setting. Methods. This cross-sectional study included 131 consecutive patients with axial SpA. The convergent (Spearman rho) and discriminant (receiver-operating characteristic [ROC] curve analysis) validity of Functional Index [BASFI], and modified Stoke Ankylosing Spondylitis Spinal Score [mSASSS]). A multivariate model was built to detect disease factors associated with RAPID3 remission (values <= 3). Results. The study included 82 men and 49 women, with a median age of 55 (IQR 46-61) years, and a median disease duration of 11 (IQR 6-24) years. Mean RAPID3 was 9.45 +/- 6.7. The BASDAI showed moderate correlation with ASDAS (rho 0.66, P < 0.0001), but higher correlations with BASFI (rho 0.78, P < 0.0001) and RAPID3 (rho 0.75, P < 0.0001). The ASDAS had moderate correlations with BASFI, BASDAI, and RAPID3 (ranges 0.66-0.68, P < 0.0001). Higher correlations were found between BASFI and BASDAI (rho 0.78, P < 0.0001), and BASFI and RAPID3 (rho 0.73, P < 0.0001). The mSASSS did not show any correlation with any of the above composite measures. Kappa agreement between RAPID3 remission and other SpA remission criteria was moderate (Kappa 0.46-0.56). The RAPID3 thresholds to define remission ranged from values <= 2 to <= 6 with areas under the ROC curve between 0.86-0.91. Female sex (OR 0.34, 95% CI 0.12-0.90, P = 0.03) and nonsteroidal antiinflammatory drug intake (OR 0.26, 95% CI 0.10-0.66, P = 0.005) were independently associated with lower odds of achieving RAPID3 remission. Conclusion. RAPID3 demonstrated construct validity in this cross-sectional study. This index can be useful for a more comprehensive assessment of axSpA in busy clinical settings.

Automated summary

The study tested the measurement properties of RAPID3 in patients with axial SpA in a real-world clinical setting and found that this index demonstrated construct validity, making it useful for a more comprehensive assessment of axSpA in busy clinical settings.