Self-reporting instruments in rheumatoid arthritis

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Abstract

BACKGROUND

The disease activity score (DAS) is used to measure disease activity in patients with rheumatoid arthritis (RA). The DAS28 ranges from 0-10 (higher scores indicating higher disease activity), and is comprised of a 28-joint count for swelling and tenderness, an erythrocyte sedimentation rate, and a patient general health score measured by a visual analogue scale (VAS-GH).

OBJECTIVE

The objective of this study was to investigate the relationship between disease activity as measured by DAS28 and patient self-report measures of disease activity, including general health, pain, and functional disability in patients with RA.

DESIGN AND INTERVENTION

This study included data from patients of two ongoing observational cohort studies. Both cohorts included patients with newly diagnosed RA (disease duration <1 year), who had not previously received treatment with disease-modifying antirheumatic drugs. The patients in both cohorts were treated at the discretion of their rheumatologist, and were assessed by a nurse at 3-month intervals. Data obtained at patient assessments included the following: DAS28 scores, VAS-GH, pain and patient disease activity, measured by VAS, and scores on a health assessment questionnaire (HAQ) measuring functional disability. The present study included data obtained in the first 3 years after diagnosis in the two cohort studies. Statistical analyses using linear regression models were used to determine relationships between disease activity measured by DAS28 and disease activity measured by patient self-report.

OUTCOME MEASURES

The primary outcome measures of this study were disease activity measured by the DAS28 and patient general health measured by VAS. Secondary outcome measures were VAS scores of pain, VAS scores of disease activity (VAS-DA), both of which were measured by the patient, and results of the HAQ on functional disability.

RESULTS

A total of 624 patients with RA, who had newly diagnosed disease and had completed 3 years of follow-up were included in this study. The majority of participants were female (65.5%) and tested positive for rheumatoid factor (76.8%). The authors found that VAS-GH was significantly associated with the DAS28 throughout the study period (P<0.0001), however the variance was low (6.7% at baseline and at the end of the study). Analysis showed that despite maintaining the same levels of disease activity, patients perceived improved general health later in the disease course, but worse function capacity over time.

CONCLUSION

The authors conclude that there is a weak association between patient reported general health (using the VAS-GH) and clinically measured disease activity (using the DAS28). It was also noted that patient perception of general health improves later on in the disease course, compared with patient perception of general health at first diagnosis.

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