- Top of page
- PATIENTS AND METHODS
Rheumatoid arthritis (RA) is a chronic, inflammatory, systemic disease, with an unpredictable course varying from mild to very severe. Patients with RA mostly experience pain and swelling in affected joints and generalized stiffness, especially in the morning. The disease has great influence on functional ability and quality of life. The goal of medical treatment of RA is to suppress disease activity and, consequently, to prevent joint damage and enhance the patient's quality of life.
Patients with RA are assessed in clinical trials and clinical practice using a core set of measurements consisting of a swollen joint count and tender joint count, assessment of acute phase reactants, physician's global assessment of disease activity, patient's global assessment of disease activity, assessment of general health and pain, and the assessment of functional ability (1). An index of disease activity for patients with RA, the Disease Activity Score in 28 joints (DAS28), can be calculated on the basis of the 28-joint count for swelling, 28-joint count for tenderness, erythrocyte sedimentation rate (ESR), and a visual analog scale (VAS) for general health (2). Response to treatment can be assessed by the American College of Rheumatology (ACR) 20% response criteria (3) or the European League Against Rheumatism (EULAR) response criteria (4).
Recently, it was demonstrated that a combination of the Health Assessment Questionnaire (HAQ), VAS pain, and patient global assessment (VAS or Likert scale) appeared to be as equally informative as the ACR20 response criteria or EULAR response criteria in distinguishing between active treatment and placebo treatment (5, 6). Subsequently, the use of only self-reporting instruments instead of physician-assessed disease activity instruments was suggested to evaluate results of drug therapy in clinical trials, observational studies, and clinical practice (7). Besides the ability to discriminate between responders and nonresponders, self-reporting instruments are very easy to administer. Patients can complete the instruments while waiting for the physician and the physician can scan them in approximately <30 seconds (5).
In all fields of medicine, clinical variables are closely related to the pathophysiologic process (i.e., blood pressure in hypertension, blood glucose concentration in diabetes, and disease activity in RA). Implicitly, clinicians assume that when they improve those clinical parameters, they will also improve the patient's quality of life and overall well-being. When using measures of functional disability and overall well-being to evaluate treatment in RA, as suggested recently, it is assumed that a change in inflammatory-related parameters is reflected in a change in overall well-being parameters. However, how valid is such an assumption?
It is well known that standards by which individuals assess their own health status can change over time (8–10), and therefore one should be cautious when using subjective, self-reporting instruments to evaluate treatment. Changes in health are accompanied by processes of readjustment, reassessment, and coping (11). When a patient is newly diagnosed with a disease, coping and, consequently, adaptation to the disease are probably barely present. In that case, the perception of health is likely to be associated with the objectively measured clinical status. Later in the disease course, the symptoms can still be present, but the patient is better able to cope with them. In this case, the health perception will often be better than one would expect based on the patient's objectively measured clinical status (9).
The objective of this study was to explore the association between objectively measured clinical status (as measured by the DAS28 excluding the VAS) and subjective perception of health in patients with RA. Further, we tested the hypothesis that later in the disease course the perception of health is better than one would expect based on the disease activity of the patient, compared with shortly after diagnosis.
- Top of page
- PATIENTS AND METHODS
Recently, the use of patient self-reporting instruments instead of clinical, objective measurements to assess patients with RA in clinical trials, observational studies, and clinical practice was proposed (7). The use of subjective, self-reporting instruments assumes at least a moderate and constant association between objectively measured disease activity and the data of self-reporting instruments. Analyses showed that there is an association, although weak, between subjective patient self-reporting instruments (VAS-GH) and objective clinical measures (DAS28). More importantly, it was demonstrated that the patient's perception of general health is better, given the same disease activity (DAS28) later in the disease course as compared with shortly after diagnosis. Similar results were seen from analyses with the VAS pain and the VAS-DA as outcome measures.
This incongruence over time between objectively measured and self-perceived health has implications for interpreting subjective, self-reporting instrument data in the evaluation of treatments. It emphasizes the fact that disease activity and the patient's perception of health, disease activity, and pain should be measured complementary to each other.
An important goal in managing RA is to prevent or control joint damage and loss of function and decrease pain (14). Recently, it was demonstrated that a therapeutic strategy intended for tight control of disease activity (measured with the original DAS) improved disease activity, radiographic disease progression, physical functioning, and quality of life compared with routine outpatient care (15). It is unknown what the effect will be of a treatment strategy intended for improving patients' perception of general health or functional ability on joint damage or disease activity later in the disease course. There is broad agreement on the fact that the goal of medical treatment should be to suppress disease activity and prevent joint damage. However, patients' self-reported well-being, pain, and disease activity are of major concern in making treatment decisions.
The incongruence over time between objectively measured and self-reported health might be associated with response shift effects (10). Possible causes of such a response shift might be adaptation and coping strategies, social comparison (16), information bias in time (learning processes) (17), or a change in expectations (18). At presentation of a disease (such as RA), there will be great anxiety about the future prospects and the unknown course of the disease, which will be reflected in measures of well-being. After a few months, patients have learned about the treatment options and their prospects, and they start to cope with their disease and subconsciously compare themselves with other patients with RA. Standards by which individuals assess their own health status are dynamic, and therefore response shift processes as described here can occur with every life event experienced by an individual patient.
Further, general health is an encompassing construct, of which disease activity is only one aspect. Other factors like social functioning, fatigue, and depression play a part in general health and are not captured by the DAS28. This also applies more or less to self-reported disease activity, pain, and functionality. Recent randomized controlled trials in rheumatology including all core set measures as well as measures of overall well-being demonstrated a smaller effect on health-related quality of life measures than on disease activity measures (19, 20). Together, this is why self-reported measures of functionality, disease activity, and general health cannot substitute objective measures of disease activity in RA; subsequently, both need to be measured.
Analyses with the HAQ as an outcome parameter showed conflicting results. One explanation might be that the HAQ is a more objective self-reporting questionnaire and is therefore less susceptible for possible response shift effects. Second, joint destruction could affect functional disability besides disease activity. Analyses showed that the effect of joint destruction on the HAQ almost reached statistical significance (P = 0.07). A last possible explanation for the increase in HAQ scores, despite a decrease in disease activity, could be that HAQ scores increase with increasing age in the RA population as well as in the general population (21).
Some limitations of this study should be mentioned. First, the DAS28 was used as the only objective variable associated with the patient's subjective general health assessments. The DAS28 was chosen because the purpose of this study was to explore the relationship between objective and subjective measures in RA, and in our opinion the DAS28 is the most objective measure in this field. Further, it is possible that other variables are associated with the general health perception of patients with RA as well; however, longitudinal regression analysis including variables such as sex, age, and functional disability did not change the independent association between time and VAS in either magnitude or direction. Finally, there were less data available on the VAS-DA and the HAQ, therefore results of analyses with these parameters are less robust.
It can be concluded that the patient's perception of health can be different with equal disease activity, depending on the moment in the disease course. Furthermore, our results indicate that self-reported measures of functionality, disease activity, and general health cannot substitute objective measures of disease activity in RA in longitudinal studies; subsequently, both need to be measured.