Quantitative measures for assessing rheumatoid arthritis in clinical trials and clinical care

There is no single 'gold standard' quantitative measure to assess and monitor the clinical status in patients with rheumatoid arthritis (RA). Therefore, a variety of measures have been used in clinical research and clinical care, including laboratory tests, radiographic scores, formal joint counts, physical measures of functional status, global measures and patient self-report questionnaires. These measures may address disease activity, joint damage, both activity and damage, or long-term outcomes. Measures of disease activity, such as joint swelling, are reversible and are emphasized in clinical trials. However, activity measures may be improved over 5 years while measures of damage, such as radiographic score, indicate disease progression. Two quantitative indices which are widely used in clinical trials are the (1) American College of Rheumatology (ACR) Core Data Set, which includes swollen joint count, tender joint count, physician assessment of global status, acute-phase reactant-erythrocyte sedimentation rate or C-reactive protein, functional status, pain, patient estimate of global status, a radiograph in studies over 1 year or longer, and (2) the disease activity score(DAs), which includes a swollen joint count, tender joint count, acute-phase reactant, and patient assessment of global status. Randomized controlled clinical trials provide the optimal method to evaluate new therapies, by comparing a therapy with a placebo or another therapy without selecting patients for specific therapies. However, randomized trials in chronic diseases have important limitations, including a relatively short observation period, patient selection for inclusion and exclusion criteria, inflexible dosage schedules, influence of the design on results despite a control group, emphasis on group data while ignoring individual variation in treatment responses, non-standardized interpretation of adverse effects, and others. Therefore, clinical trials in RA must be supplemented by long-term observational studies to assess results of therapy in regard to long-term outcomes such as work disability, joint replacement surgery and premature mortality. The most simple and effective method of collecting important long-term data from patients in routine clinical care is through patient self-report questionnaires.