Advantages and limitations of quantitative measures to assess rheumatoid arthritis: joint counts, radiographs,...

Medical care is advanced by quantitative measures, all of which have advantages and limitations. No single "gold standard" measure, analogous to blood pressure, is available for diagnosis, prognosis, and management of rheumatoid arthritis (RA). Four types of measures have been used, including joint counts, radiographs, laboratory tests, and patient questionnaires. Joint counts are the most specific measure for RA but are poorly reproducible and not performed in most standard care. Radiographs provide an objective record of joint damage, but are scored quantitatively only in clinical research and have little prognostic value for long-term outcomes such as work disability and mortality. Laboratory tests are helpful when positive but frequently are "false negative"--for example, rheumatoid factor (RF), erythrocyte sedimentation rate, or C-reactive protein are normal in 30% to 45% of patients. "False positive" results are also seen; most people with RF or antinuclear antibody do not have a disease. Patient questionnaires are useful to assess and monitor patient status and provide the most significant predictive measures for long-term work disability and mortality. A multidimensional health assessment questionnaire is useful in all rheumatic diseases, with scoring templates and medical history information to save time for the rheumatologist and patient in standard care.