Background Functional outcomes are central in patients with chronic inflammatory musculoskeletal diseases. It has been shown in rheumatoid arthritis that functional outcomes are impaired in the presence of structural damage, a finding that has not yet been investigated in psoriatic arthritis (PsA), which has a more complex phenotype than rheumatoid arthritis (RA).
Objectives To quantify the association of radiographic damage with physical function in PsA patients.
Methods We analysed patients enrolled in the GO-REVEAL study1 who had received golimumab. We obtained modified Sharp-van-der-Heijde scores (mSvDHS) from X-rays, performed at week 0, 24, 52 and week 104 (n=262). In longitudinal data analysis, we then used generalized estimating equations (GEE) on all patients in DAPSA remission (n=96), utilising all their remission visits, whereby the health assessment questionnaire (HAQ) disability index of each patients visit was used as dependent variable and mSvDHS, joint space narrowing (JSN) and erosion (ERO) scores, respectively, were used as independent variables in separate models.
To analyse effects of structural damage on changeability of functional limitations, we identified a subgroup of patients who had functional limitations at baseline (HAQ≥1) and who showed a major response of DAPSA (improvement of ≥85% from baseline). In this model we assess the effect of mSvDHS on changes in HAQ, while adjusting for HAQ at baseline (n=54).
As validation cohort, we analysed a routine clinic PsA cohort with complete cDAPSA (the clinical version of the DAPSA without CRP) and mSvDHS (n=99). A cDAPSA cutoff of ≤4 was used to define the remission cohort in an analogous way as decribed above (n=32).
Results As shown in table 1 and visualised in figure 1A, for patients in DAPSA remission, significant effects were seen for mSvDHS, JSN and ERO. These results could be confirmed in the validation cohort with patients achieving cDAPSA remission and showed a significant association of HAQ and mSvDHS (Estimate=0.0044, p=0.0176) as well as JSN (Estimate=0.0078, p=0.0165).
In the second analysis, looking at patients achieving DAPSA major response, again, results were significant for the association total mSVDHS and JSN. Additionally, higher estimates of JSN, compared to mSvDHS could be observed, with relative HAQ change as outcome parameter (see table 1 and figure 1B).
Conclusions Our results suggest that in JSN is functionally more important than erosions. Functional outcomes have an irreversible component that is strongly related to the amount of structural damage. This needs to be considered when targeting functional outcomes in clinical practice.
Kavanaugh A, van der Heijde D, McInnes IB, et al. Golimumab in psoriatic arthritis: one-year clinical efficacy, radiographic, and safety results from a phase III, randomized, placebo-controlled trial. Arthritis Rheum 2012; 64: 2504–2517.
We thank Janssen for provision of an 80% random data cut of patients in the GO-REVEAL trial for our analyses.
Disclosure of Interest None declared