Objective Although there are different tools to evaluate axial spondyloarthritis (axSpA), they are hardly used in clinical routine due to time constraints. The Routine Assessment of Patient Index Data 3 (RAPID3) is a composite measure feasible to be used as a sole metric in busy clinics. We aimed to test its measurement properties in patients with axial SpA in a real clinical setting. Methods Cross-sectional study that included 131 consecutive patients with axial SpA. The convergent (Spearman's rho) and discriminant (ROC curve analysis) validity of RAPID3 were tested against several axSpA-specific measures (BASDAI, ASDAS, BASFI, 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, median age of 55 years (IQR: 46-61), and median disease duration of 11 years (IQR: 6-24). Mean RAPID3 was 9.45 ± 6.7. The BASDAI showed moderate correlation with ASDAS (rho: 0.66, p < 0.0001), but higher 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 from 0.66 to 0.68, p < 0.0001). Higher correlations were found between BASFI and BASDAI (rho: 0.78, p < 0.0001) and BASFI-RAPID3 (rho: 0.73, p < 0.0001). The m-SASSS did not show any correlation with any of the afore-mentioned composite measures. Kappa agreement between RAPID3 remission and other SpA remission criteria was moderate (k: 0.46-0.56). The RAPID3 thresholds to define remission ranged from values ≤2 to ≤ 6 with areas under the ROC curves between 0.86 and 0.91. Female sex (OR 0.34, 95%CI: 0.12- 0.90, p= 0.031) and NSAIDs 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.