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Health-related quality of life in patients with psoriatic and rheumatoid arthritis: data from the prospective multicentre NOR-DMARD study compared with Norwegian general population controls
  1. Brigitte Michelsen1,2,3,
  2. Till Uhlig1,4,
  3. Joseph Sexton1,
  4. Désirée van der Heijde1,5,
  5. Hilde Berner Hammer1,
  6. Eirik Klami Kristianslund1,
  7. Ada Wierød6,
  8. Gunnstein Bakland7,
  9. Erik Rødevand8,
  10. Frode Krøll9,
  11. Jon Håvard Loge4,
  12. Glenn Haugeberg2,3,
  13. Tore K Kvien1,4
  1. 1 Department of Rheumatology, Diakonhjemmet Hospital, Oslo, Norway
  2. 2 Division of Rheumatology, Department of Medicine, Hospital of Southern Norway Trust, Kristiansand, Norway
  3. 3 Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway
  4. 4 Faculty of Medicine, University of Oslo, Oslo, Norway
  5. 5 Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
  6. 6 Department of Rheumatology, Vestre Viken/Drammen Hospital, Drammen, Norway
  7. 7 Department of Rheumatology, University Hospital of Northern Norway, Tromsø, Norway
  8. 8 Department of Rheumatology, St. Olavs Hospital, Trondheim, Norway
  9. 9 Department of Rheumatology, Lillehammer Hospital for Rheumatic Diseases, Lillehammer, Norway
  1. Correspondence to Dr Brigitte Michelsen, Department of Rheumatology, Diakonhjemmet Hospital, Oslo 0370, Norway; brigitte_michelsen{at}yahoo.no

Abstract

Objectives To compare (1) Short Form-36 (SF-36) Physical Component Summary (PCS) and Mental Component Summary (MCS), scale scores and Short Form-6 dimensions (SF-6D) between patients with rheumatoid arthritis (RA) and patients with psoriatic arthritis (PsA) and Norwegian general population controls and (2) improvements in these measures between patients with RA and PsA.

Methods Analyses of covariance were performed to compare SF-36 measures between first-time enrolled patients with RA (n=3898) and PsA (n=1515) from the prospective observational multicentre NORwegian-Disease Modifying Anti-Rheumatic Drug study (6 months follow-up) and general population controls (n=2323).

Results In age and gender-adjusted analyses, patients with PsA compared with patients with RA had similar PCS, MCS and SF-6D (p≥0.14), worse vitality and general health, but better physical functioning at 0/6 months (p≤0.03). With additional 28-joint disease activity scores adjustment as a proxy for joint inflammation, PCS, most scale scores and SF-6D were worse in patients with PsA than patients with RA at 0/3/6 months (p≤0.01). PCS was more impaired than MCS both in RA and PsA compared with general population controls (p≤0.001). Mean 3-month and 6-month improvements after disease-modifying anti-rheumatic drug treatment were larger in patients with RA than patients with PsA for bodily pain, vitality and mental health (p≤0.02).

Conclusions Health-related quality of life was overall similar in patients with RA and patients with PsA—with a tendency to worse scores in PsA—and worse compared with Norwegian general population controls.

  • psoriatic arthritis
  • rheumatoid arthritis
  • outcomes research
  • patient perspective

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Introduction

Health-related quality of life (HRQoL) is part of the core set of data to be collected in patients with psoriatic arthritis (PsA) and recognised to be of major importance also in other rheumatic diseases, including rheumatoid arthritis (RA).1 2 HRQoL has been found to be impaired in patients with inflammatory arthritides compared with the general population.3–6 In smaller observational studies performed 1–2 decades ago, similar HRQoL in patients with RA and patients with PsA were described7 8 and also differences in Short Form-36 (SF-36) scale scores.5

To our knowledge no large, prospective observational study has compared HRQoL between patients with RA and patients with PsA and the general population using the widely recognised SF-36.

The aim of this study was to compare SF-36 Physical Component Summary (PCS) and Mental Component Summary (MCS), scale scores as well as Short Form-6 dimensions utility score (SF-6D) between patients with RA and patients with PsA from a large prospective observational study, as well as with general population controls. Furthermore, we aimed to compare improvements in PCS, MCS and scale scores between patients with RA and patients with PsA from baseline to 3-month and 6-month follow-ups after initiation of treatment with disease-modifying anti-rheumatic drugs (DMARDs).

Methods

Patients

We included first-time enrolled patients with RA and patients with PsA from the prospective longitudinal observational multicentre NORwegian-Disease Modifying Anti-Rheumatic Drug (NOR-DMARD) study,9 10 starting synthetic and/or biological DMARDs between 1 December 2000 and 6 November 2012 and followed until 1 May 2013 or until stopping DMARD medication. The RA and PsA diagnoses were given by the treating rheumatologist after clinical judgement. Analyses included baseline, 3-month and 6-month follow-ups. Written informed consent was obtained from each patient. For comparison, we included SF-36 Norwegian normative data from 2323 individuals collected in 1996.11

SF-36 and SF-6D

The Norwegian translation of SF-36 version 1, used in this study, is validated in Norwegian patients with RA.12 PCS and MCS were calculated as described by Ware et al.13 Norm-based scale scores were computed by subtracting the general population’s respective mean scale score from the 0–100 scale scores, divided by the SD of the data from the general population. Each of these values were multiplied by 10 and 50 was added, as described by Ware et al.14 SF-6D was calculated from SF-36 according to the algorithm developed by Brazier et al.15

Statistics

Demographic and baseline characteristics are shown as medians (25th and 75th percentiles) for non-normally distributed data and means (SD) for normally distributed data. Continuous variables were compared using independent t-test, Mann-Whitney U test or analysis of variance, as appropriate. Prespecified age and gender-adjusted analyses of covariance were performed to compare PCS, MCS, scale scores and SF-6D between patients with RA, patients with PsA and general population controls at baseline, and between RA and PsA patients with and without additional adjustment for the respective 28-joint disease activity scores (DAS28) at baseline and after 3-month and 6-month follow-up. Prespecified ANCOVA were performed to compare changes in PCS, MCS, scale scores and SF-6D from baseline to 3-month and 6-month follow-up, adjusted for age, gender and the respective baseline values. Radar diagrams were made to visualise differences in scale scores between patients with RA/PsA and the Norwegian general population. Statistical tests were performed using SPSS V.23.0 for Windows. The analyses were performed as completer analyses and without adjustment for multiple comparisons.

Results

Patients with RA (n=3898), patients with PsA (n=1515) and general population controls (n=2323) had mean (SD) age 55.9 (31.6)/48.1 (12.6)/44.9 (16.5) years and 71.4%/50.3%/51.3% were females, respectively. Baseline mean (SD) DAS28 was worse in patients with RA (4.9 (1.4)) than patients with PsA (4.2 (1.3)) (online supplementary table S1).

Supplemental material

Analyses adjusted for age and gender

SF-36 PCS, MCS, scale scores and SF-6D were worse in patients with RA and patients with PsA compared with the general population (table 1) but improved during follow-up (online supplementary table S2).

Table 1

Unadjusted analyses and analyses adjusted for age and gender of baseline SF-36 component summaries, norm-based scale scores and SF-6D utility scores

PCS and MCS were not statistically different in patients with RA compared with patients with PsA, while physical functioning was better and general health and vitality worse in patients with PsA at all time-points. Bodily pain was similar between patients with RA and patients with PsA at baseline but slightly worse in patients with PsA at 3 and 6 months (table 1, online supplementary table S2).

Analyses adjusted for age, gender and DAS28

In analyses adjusted for DAS28 in addition to age and gender, patients with PsA had significantly worse PCS and SF-6D at all time-points compared with patients with RA. Baseline MCS and all scale scores, except role emotional, were worse in PsA compared with patients with RA. At 3 and 6 months bodily pain, general health, vitality, social functioning and mental health were worse, and the remaining scale scores were similar in patients with PsA compared with patients with RA (online supplementary table S3).

Longitudinal analyses adjusted for age, gender and baseline values of the respective scores

Patients with RA and patients with PsA had similar improvements in PCS, MCS, all scale scores and SF-6D at 3 and 6 months, except for larger improvements in bodily pain, vitality and mental health in the patients with RA (table 2, adjusted analyses and supplementary table S4, unadjusted analyses).

Table 2

Mean improvements from baseline until 3-month and 6-month follow-up, adjusted for age, gender and the respective baseline values

Graphical comparisons of scale scores

Estimated marginal means of baseline, 3-month and 6-month SF-36 scale scores adjusted for age and gender (figure 1) as well as DAS28 (figure not shown) were impaired in patients with RA and patients with PsA compared with the general population but showed only small differences between patients with RA and patients with PsA.

Figure 1

Estimated marginal means adjusted for age and gender of baseline and 3-month (A) and 6-month (B) norm-based scale scores in patients with rheumatoid arthritis (RA) (n=3898) and patients with psoriatic arthritis (PsA) (n=1515) compared with general population controls (n=2323).

Discussion

In this large prospective observational multicentre study, SF-36 PCS, MCS as well as the utility measure SF-6D were comparable between patients with RA and patients with PsA at baseline and at 6-month follow-up in age and gender-adjusted analyses. Furthermore, patients with PsA had worse general health and vitality but better physical functioning at all time-points, as well as more bodily pain at 3 and 6 months. With adjustment for DAS28 in addition to age and gender, patients with PsA compared with patients with RA had worse PCS, SF-6D, general health, vitality, bodily pain, social functioning and mental health at all time-points.

Furthermore, the study shows that levels of physical HRQoL were more impaired than mental HRQoL in patients with RA and PsA compared with Norwegian general population controls.

Improvements in scale scores from baseline until 3 months and 6 months were similar between patients with RA and patients with PsA during treatment with DMARDs, except for larger improvements in bodily pain, vitality and mental health in RA.

We have chosen to present norm-based scale scores to facilitate interpretation and comparison across different countries and populations.14 16 Still, interpretation of the findings is not straight-forward; the statistically significant differences between patients with RA and patients with PsA may not always be clinically significant. As visualised in radar diagrams (figure 1), the differences in scale scores between patients with RA and patients with PsA are small. Still, for example for general health the difference between RA and PsA patients at different time-points is of similar magnitude as the improvement in general health from baseline until 6 months both for patients with RA and patients with PsA and hence of probable clinical significance.

The study underlines the severe impact of both RA and PsA on HRQoL reflected through SF-36, which is in line with a smaller observational study3 as well as clinical trials.4 17 18 Furthermore, the study highlights the relatively stronger impairment of HRQoL in patients with PsA compared with patients with RA, when also taking into consideration levels of joint inflammation, as measured by DAS28. Notably, also according to PsA patients’ perspective HRQoL is of great importance.1 The severe impact of PsA on HRQoL may possibly be explained by extra-articular inflammatory affection of, for example, skin or entheses. However, NOR-DMARD does not have data on these disease manifestations. We were therefore unable to identify which disease manifestations that contributed most to the reduced HRQoL in PsA. Of note, general health and vitality were worse in patients with PsA compared with patients with RA in all adjusted analyses at all time-points.

Patients with RA as well as patients with PsA reported better mental than physical HRQoL, which is in line with smaller observational studies on SF-36,3 as well as with clinical trials.4 17 Interestingly, the RA and PsA scale score profiles (figure 1) were similar to the RA scale score profile found by Strand and Singh.17

Furthermore, the study is partly in line with two considerably smaller NOR-DMARD studies reporting better 6-month improvements in bodily pain and vitality but not mental health in patients with RA compared with patients with PsA.19 20 These studies did not include general population controls.

The generic SF-36 facilitated comparison of HRQoL across diseases, although it might capture somewhat different aspects of HRQoL than disease-specific measures, for example, the psoriatic arthritis quality of life.21

Limitations of the study include lack of 66/68 joint count as well as lack of measures of PsA inflammatory activity other than arthritis (eg, skin involvement, enthesitis, dactylitis and spondylitis), which may have led to underestimation of disease activity in PsA as used in the DAS28-adjusted analyses. Lack of adjustment for comorbidities may have biased the results, although partly corrected for by the age adjustment. Furthermore, completer analyses may have affected the generalisability of the results.

The major strength of the study is the prospective observational multicentre design including large cohorts of patients with RA and patients with PsA over a long time span, as well as Norwegian general population controls. To our knowledge, this is the largest prospective observational study comparing SF-36 between RA and PsA patients, and the first to compare SF-36 component summaries, scale scores as well as SF-6D between patients with RA and patients with PsA and general population controls in the same analyses.

In conclusion, HRQoL was overall similar in patients with RA and PsA—with a tendency to worse scores in PsA—and worse compared with Norwegian general population controls.

Acknowledgments

The authors would like to thank the patients for participating in this study and the local rheumatology staff for data collection. Manuscripts based on work previously presented at a conference and published as a conference abstract should state this in the Acknowledgements section: Michelsen B et al. Arthritis Rheum 2017; 69 (suppl 10) and Michelsen B et al. Ann Rheum Dis 2017;76 (supple 2):97.

References

Footnotes

  • Contributors BM, TU, JS, DvdH, HBH, EKK, JHL, GH and TKK were responsible for study design. TU, AW, GB, ER, FK and TKK were responsible for data acquisition. BM analysed the data and wrote the manuscript. All authors critically revised the manuscript and approved the final version.

  • Funding The study was funded through clinical research fellowships from Diakonhjemmet Hospital (originating from South-Eastern Health Authority) and from The Hospital of Southern Norway Trust and through a grant from Grethe Harbitz’ Legacy. Data collection in NOR-DMARD was partly funded through unrestricted grants from Abbvie, BMS, MSD, Pfizer (Wyeth), Roche and UCB.

  • Competing interests None declared.

  • Patient consent Not required.

  • Ethics approval The study was approved by the National Data Inspectorate and by the Regional Committee for Medical and Health Research Ethics in Eastern Norway.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement All relevant data are within the text.