Measures of arthritis activity associated with patient-reported improvement in rheumatoid arthritis when assessed prospectively versus retrospectively.

The patient global assessment (PGA) occupies a central place among measures of rheumatoid arthritis (RA). Not only is the PGA one of the core measures in the American College of Rheumatology (ACR) response criteria, but it is the only patient-reported measure included in composite RA activity measures and in new criteria for remission. The PGA is an attractive measure because it is intended to capture, in a single item, an overall summary of the impact of RA on a patient's well-being. .However, its loosely-defined nature may contribute to wide variation among patients in the aspects of RA that are emphasized in marking the PGA, and which may be influenced by mood or other psychological factors. In several cross-sectional analyses, pain severity was the dominant influence on the PGA, accounting for up to 75% of inter-patient variation in ratings (1–7). Physical functioning, fatigue, depression, and in some studies, joint counts, were also important. The relative contribution of these features is difficult to assess because not all studies included measures of depression, fatigue, stiffness, or joint counts. A study that reported a major contribution of depression to the PGA did not include a measure of pain (8). To understand which aspects of RA influence patients’ assessments of change in their status, it is important to perform longitudinal comparisons, rather than rely on indirect between-patient comparisons of cross-sectional studies. Few longitudinal studies have investigated which RA activity measures are associated with changes in the PGA (5, 9–11). One study examined only pain and physical functioning, another only the Disease Activity Score (DAS), and the single study that examined fatigue and depression did not include joint counts. In clinical practice, informal appraisals of patients’ overall status are more common than formal measures such as the PGA. Universal questions to patients include how they feel now and if they feel better. These appraisals are retrospective judgments that, like the PGA, are intended to integrate diverse aspects of disease into a single assessment. However, because they depend on recall, changes reported retrospectively may differ from those measured prospectively on measures such as the PGA, and the validity of retrospective judgments of improvement has been questioned (12). Our first goal was to identify the RA-related measures associated with prospectively measured changes in the PGA. If changes in clinical factors other than pain were associated with changes in PGA, it would validate the PGA as a summary measure of multiple aspects of RA. We were also interested in whether depression and fatigue were independently associated with changes in the PGA. Our second goal was to identify if changes in RA activity measures were associated with patients’ retrospective judgments of improvement in overall arthritis status as a way to validate this outcome measure. Our third goal was to compare the RA activity measures that were associated with patients' retrospective judgments with those associated with the PGA. The former directly reflects the assessments provided by patients in clinical practice, and the comparison would provide insight into how patients form their appraisals of improvement.