Psychometric properties of sleep and coping numeric rating scales in rheumatoid arthritis: a subanalysis of an etanercept trial.

OBJECTIVES: In rheumatoid arthritis, quality of sleep and ability to cope are important for patients; however their usefulness as outcome measures is not well established.

METHODS: Post-hoc analysis of an open-label 12-week trial of etanercept in biologic-naïve rheumatoid arthritis patients with visits at screening, baseline and over 12 weeks. Outcomes measured included Disease Activity Score 28 erythrocyte sedimentation rate (DAS28), numeric rating scales for sleep, coping, patient and physician-global assessment, pain and fatigue, and modified-HAQ. Reliability between screening and baseline visits by intra-class correlation, and responsiveness between baseline and 12 weeks by standardised response means were assessed for each outcome.

RESULTS: In 108 patients, mean age 54 (standard deviation (SD) 13) years, mean disease duration 8 (SD 7) years, 75% women; disease activity was high at baseline: mean DAS28 5.5 (SD 0.8). Reliability intra-class correlation was 0.83[95% confidence interval: 0.77;0.88] for sleep, 0.81[0.74;0.87] for modified-HAQ, 0.80[0.71;0.86] for fatigue, 0.72[0.62;0.80] for physician-global assessment, 0.66[0.54;076] for coping, 0.65[0.53;0.75] for pain and 0.63[0.50;0.73] for patient-global assessment. Responsiveness standardised response means was 1.65[1.32;2.10] for physician-global assessment, 1.37[1.09;1.73] for pain, 1.36[1.08;1.73] for patient-global assessment, 1.15[0.95;1.41] for fatigue, 0.96[0.70;1.28] for coping, 0.92[0.73;1.15] for sleep and 0.86[0.69;1.07] for modified-HAQ.

CONCLUSIONS: Numeric rating scales assessing sleep and coping were found to be generally as reliable as 'usual' outcomes in rheumatoid arthritis. Responsiveness was less high, indicating these domains of health may be less accessible to biologic treatment. When assessing the patient's perspective on treatment, it is feasible and valid to measure sleep and coping by numeric rating scales.