Background The current standard of care for rheumatoid arthritis (RA) is treat to remission or low activity state. This underlines the need of regular assessment of disease activity. Patient-derived Disease Activity Score (PDAS) is one of the tools that have been developed and validated to allow patients with RA to self-assess disease activity.1 Two versions of PDAS are available: PDAS1 (with ESR) and PDAS2 (without ESR). The corresponding cut-off points of RA activity statuses had been reported.2 PDAS was developed in English speaking patients.
Objectives To explore the validity of PDAS in Chinese speaking RA patients.
Methods 100 RA patients were recruited from rheumatology specialist clinic in Hong Kong. They were asked to complete in Chinese version of questionnaires before clinic which included functional status (Health Assessment Questionnaire)3, self assessed swollen and tender joint count, morning stiffness and global assessment. Standard disease activity score DAS28ESR and CDAI were assessed by Rheumatologists at these visits. Correlation with PDAS1 and 2 was done with Spearman rank test and categorical agreement by kappa statistics. The study was approved by local ethics committee.
Results Patient characteristics are as follows: mean age 60 years (standard deviation SD 12), mean RA disease duration 14 years (SD 9), 90% female, 71% seropositive, 48% patients in remission or low disease activity while 52% in moderate or high disease activity. PDAS in Chinese patients showed equally high correlation with DAS28ESR and CDAI. Spearman rank correlation coefficients were similar to those in original PDAS derivation (in brackets) (all P<0.0001):
When comparing RA activity statuses ([remission or low] versus [moderate or high activity]) using kappa statistics, PDAS showed considerable agreement with DAS28ESR, noting that within this patient group, the agreement of DAS28ESR with CDAI itself was only 0.60:
In particular for PDAS2, a formula without the need of blood test, has good sensitivity (96%) of picking up DAS28 remission or low activity, and good negative predictive value (89%) to signal moderate or high activity.
Conclusions PDAS can be adapated to Chinese language speaking RA patients in routine clinical setting. PDAS2 is useful in two aspects: informing patients that they are well treated-to-target; and concuring with patients having moderate or high disease actiivity.
Choy EH et al. Arthritis Rheum. 2008 Feb 15;59(2):192–9
ACR 2012 Abstract 27063
Koh ET et al. J Rheumatol. 1998 Sep;25(9):1705–8
Disclosure of Interest None declared