FRI0525 Methodological challenges when comparing demographic and clinical characteristics of international observational studies.
Authors: S. Verstappen, J. Askling, H. Yamanaka, J. Greenberg, M. Ho, K. Michaud, D. Symmons, F. Nyberg
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> It is unknown how comparable rheumatoid arthritis/inflammatory polyarthritis (RA) registries are. Aggregating data from different rheumatoid arthritis registries (RAR) across the world for this purpose is challenging because of possible differences in design, follow-up assessment and variables assessed. Understanding these issues may also be helpful when interpreting results or pooling data from different observational registries. <h3>Objectives</h3> To compare demographic and clinical data from four international RAR including: NOAR (UK), SRR (Sweden), IOARRA (Japan) and CORRONA (USA). <h3>Methods</h3> The first comparison (full cohort) included patients with RA, both present in RAR on 01-01-2000 or entering later (defined as baseline). Predefined criteria were then applied to evaluate whether restrictions could improve comparability between the four RAR. The sub-cohort presented here comprised patients with seropositive and/or erosive RA, who received at least one previous non-biologic DMARD (nbDMARD) treatment and who switched to or added another DMARD (baseline sub-cohort). <h3>Results</h3> Overall, baseline demographic characteristics were quite similar across RAR, except for % current/past smokers. Percentage of patients with disease duration &lt;5 years ranged from 44% in CORRONA to 75% in SRR. In the full cohort, more patients in CORRONA had low disease activity compared to the other three RAR, while the percentage of patients with HAQ-score≤1.0 and RF<sup>+</sup> patients was quite similar across SRR, IORRA and CORRONA. The proportion of patients who used non-MTX nbDMARDs at baseline varied greatly. Applying a more strict cohort definition (sub-cohort) did not change these results very much, except for RF which was part of the restriction criteria. <h3>Conclusions</h3> Despite different inclusion criteria for the individual registries, it is possible to optimize the comparability across RAR by applying well-defined cohort definitions. However, even in more restricted sub-cohorts, some variability remains - possibly due to the percentage of incident or prevalent cases included in the cohorts, when disease activity is measured, and general differences in RA populations across the world. <h3>Disclosure of Interest</h3> S. Verstappen: None Declared, J. Askling Grant/research support from: AstraZeneca, Consultant for: AstraZeneca, H. Yamanaka Grant/research support from: IORRA cohort is supported by various research grants from a large number of pharmaceutical compnies including AstraZeneca, Consultant for: AstraZeneca, J. Greenberg Shareholder of: CORRONA Inc., Consultant for: CORRONA, Novartis, Pfizer, M. Ho Employee of: AstraZeneca, K. Michaud Grant/research support from: ACR Rheumatology Research Foundation; NDB receives funds from AstraZeneca, Employee of: National Data Bank for Rheumatic Diseases (NDB), D. Symmons Grant/research support from: AstraZeneca, Consultant for: AstraZeneca, F. Nyberg Employee of: AstraZeneca