Background Tender & swollen joint counts (JCs) have been identified as core domains for assessment of flare in rheumatoid arthritis (RA)1,2.
Objectives To assess the responsiveness and discriminative validity of patient-reported JCs, separately and incorporated in composite patient-reported outcomes (PROs), for worsening of disease activity in early RA (ERA).
Methods Paired data from ERA patients in the Canadian early arthritis cohort (CATCH) who prospectively completed the OMERACT preliminary flare questionnaire (PFQ) twice over a 3-month interval between 12/2011 and 5/2013 were used. Patients reported tender and swollen JCs on a 40-joint homunculus (PtTJ40, PtSJ40) and the 16-joint RA-disease-activity-index (RADAI) mannequin. Physicians assessed the TJC68, SJC66 and global assessment (MDGA). DAS28 Flare was classified as: a worsening in DAS28 >1.2 (or >0.6 if DAS28 ≥3.2) and patient flare status: `'Are you having a flare at this time?” with no changing to yes. Median changes in pt-JCs were compared between patients in a flare or not by Wilcoxon signed rank test. Discrimination of flare vs. non-flare for the pt JCs separately and incorporated into the patient-disease- activity-scores (pDAS1 and pDAS2) and routine-assessment-of-patient-index-data (RAPID4) was assessed via effect sizes (ES) and compared with ES of traditional parameters.
Results Of 115 eligible patients, 90% fulfilled the ACR 2010 RA criteria, 79% were female, mean (SD) age was 55 (15) years and symptom duration 5 (3) months. At the initial assessment, 46%/15% of the patients were in DAS28 remission/low disease activity, with a median (IQR) ptSJC40 and ptTJC40 of 1 (0-3) and 3 (1-10), respectively. Mean physician SJC66 and TJC68 were 1.9 (SD 3.3) and 4.6 (SD 6.6). After 3 months, 26 (23%) experienced a flare according to the DAS28 definition and 16 (14%) pts reported a flare. DAS28 flare was associated with a significant increase in pt JCs and PROs, physician JCs, HAQ, MDGA and ESR (Table). The composite PROs, RADAI48, physician TJCs, ESR, MDGA and pt global best discriminated flare from non-flare (ES>1). Flare according to the patient statement was associated with a significant increase in PDAS1, RAPID3 and 4, DAS28 and ESR and was discriminated best by the PDAS1, RAPID3 and 4, and physician SJC (ES>0.8).
Conclusions In ERA, a change in patient-reported JCs can identify worsening of disease activity and detect flares, with highest discriminative validity when used in composite indices. Patient derived composite indices incorporating patient JCs should be considered in developing a comprehensive definition of RA flare.
Bartlett SJ, Ann Rheum Dis 2012;71(11):1855.
Bykerk VP, J Rheumatol epub 2014.
Acknowledgements The CATCH study was designed and implemented by the investigators and financially supported initially by Amgen Canada Inc. and Pfizer Canada Inc. via an unrestricted research grant since the inception of CATCH. As of 2011, further support was provided by Hoffmann-LaRoche Ltd., UCB Canada Inc., Bristol-Myers Squibb Canada Co., AbbVie Corporation (formerly Abbott Laboratories Ltd.), and Janssen Biotech Inc. (a wholly owned subsidiary of Johnson & Johnson Inc.)
Disclosure of Interest : None declared