ObjectivesIn this study the concordance between the Routine Assessment of Patient Index Data 3 (RAPID3) and the Disease Activity Score 28-joint count (DAS28) was investigated in a clinical routine outpatient setting.Patients and methodsA sample of 150 adult patients with stable RA treated with biological DMARDs (bDMARDs) was asked to complete the RAPID3 (digital or on paper) just before their outpatient routine visit during which DAS28 assessment took place. The RAPID3 correlation with and the agreement in four DAS28 categories was studied using Spearman’s rank order and Cohen’s observed kappa statistics respectively. The positive (PPV) and negative (NPV) predictive values were calculated to test whether RAPID3 could make distinction in active disease (DAS28 >3.2) or not.ResultsA moderate correlation (ρ 0.576) and a poor kappa value of 0.13 were found in the whole study population. Patients reported a higher disease severity than was measured by DAS28. The PPV of RAPID3 for active disease by DAS28 was 0.59 (95 % CI 0.50–0.68) and the NPV was 0.91 (95 % CI 0.75–0.98) with a sensitivity and specificity of 96 and 40 % respectively.DiscussionWhile RAPID3 correlates to some extent with DAS28 at the group level, agreement between RAPID3 and DAS28 at the individual patient level is to poor to rely on RAPID3 results in monitoring patients with RA. RAPID3 tends to over-report disease activity as assessed by DAS28.