Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects the joints and surrounding tissues in the hands and feet. It occurs when the body’s immune system mistakenly attacks the membranes that line the small joints in the hands and feet. Signs and symptoms of RA include tender, swollen joints, prolonged morning stiffness, nodules under the skin on the arms, as well as fatigue, fever, and weight loss. Numbness, tingling, and burning sensations in the hands and feet may also be signs of rheumatoid arthritis. In the early stages, RA tends to predominantly affect the smaller joints in the body, but as it progresses, symptoms may spread to larger joints, such as the knees, elbows, hips, and shoulders. For most individuals with RA, symptoms tend to occur on both sides of the body. The signs and symptoms of RA also range from mild to severe, and can wax and wane, with some individuals even experiencing periods of relative remission. However, over time, the chronic inflammation associated with RA can cause joints to become deformed and dislocated.
Much like fibromyalgia, RA most commonly affects middle aged women, and individuals with previously affected family members may have an increased risk of developing RA. Although there are no specific lab tests to definitively determine if an individual has RA, several blood tests may be helpful to distinguish between RA and fibromyalgia, including the rheumatoid factor test and anti-CCP antibody test. Furthermore, joint swelling and deformity is extremely characteristic of RA and not of fibromyalgia, which can aid in the differential diagnosis (Goldenberg, 2009).
Research on Fibromyalgia and Rheumatoid Arthritis
Approximately 10-20% of patients with RA also have a diagnosis of fibromyalgia. In a 2011 review article that examined the prevalence of fibromyalgia in patients with other chronic pain conditions, Yunus found a mean prevalence of 15.4% for fibromyalgia. A 2010 study conducted by Wolfe et al. determined the rate of future fibromyalgia development among RA patients. The researchers evaluated cumulative health records of over 9,700 patients with RA using the American College of Rheumatology (ACR) 2010 diagnostic criteria for fibromyalgia. They found that 7.4% of the patients satisfied the criteria for a diagnosis of fibromyalgia during the follow-up period (Wolfe et al., 2010).
Those patients who have a dual diagnosis of fibromyalgia and RA tend to have greater measures of pain, impaired functioning, disease activity, and psychological distress (Wolfe et al., 1984; Yunus, 2012). In 2004, Wolfe & Michaud examined survey data from 11,866 patients with RA. Of these patients, 17.1% (1,731) met the criteria for a diagnosis of fibromyalgia. After analyzing a number of physical and demographic characteristics of the patients, the researchers concluded that patients who have both RA and fibromyalgia experience higher rates of hospitalization for comorbid conditions, higher rates of high blood pressure, cardiovascular disease, and diabetes, and depression. Not surprisingly, those with both RA and fibromyalgia demonstrated more severe physical and mental symptoms, and negative impact on quality of life (Wolfe & Michaud, 2004).
The characteristic joint deformity and swelling associated with RA usually aids greatly in distinguishing it from fibromyalgia, however Friend & Bennett (2011) recently evaluated several questionnaire-based methods to aid in diagnosis between the two. The researchers evaluated the Revised Fibromyalgia Impact Questionnaire (FIQR) and the recently developed variant Symptom Impact Questionnaire (SIQR) to discriminate between features that can help differentiate between fibromyalgia and RA, as well as systemic lupus erythematosus (i.e., “lupus”). After administering various combinations of questions from the two questionnaires to patients with all three diseases, the researchers found a combination of questions that resulted in the correct diagnosis for 97% of patients, leaving only 7 of 253 patients mis-classified. The implications of this research are important in that they provide clinicians with important guidance on how to best distinguish RA patients from fibromyalgia patients when using questionnaire-based diagnostic tools (Friend & Bennett, 2011).