Approach

The diagnosis of rheumatoid arthritis (RA) is made on the basis of the clinical manifestations of the disease. Laboratory tests or radiographic examinations can be useful in determining prognostic information, but are not essential for making a diagnosis. Patients are referred to a rheumatologist for confirmation of diagnosis.

Classification criteria have been published in an attempt to diagnose RA earlier in the disease course.[48][Figure caption and citation for the preceding image starts]: Rheumatoid arthritis (chronic hand deformities)From the collection of Dr Soumya Chatterjee [Citation ends].com.bmj.content.model.Caption@16a1ab03

Early diagnosis and treatment is associated with improved outcomes, and is an important principle of management.[49]

Workup and treatment should not be delayed while waiting for all RA criteria to be fulfilled; however, there is still a good chance that undifferentiated polyarthritis of <6 weeks' duration will subside spontaneously.

Clinical presentation

Most patients present between the ages of 40 and 60 years.[50] Patients who meet diagnostic criteria for RA usually present with a history of bilateral, symmetric pain and swelling of the small joints of the hands and feet that has lasted for more than 6 weeks. Morning stiffness lasting over 1 hour is commonly reported but can also be seen in other inflammatory conditions. Extra-articular features (e.g., rheumatoid nodules over the extensor surfaces of tendons or vasculitic skin involvement) may be seen but are less common.

Swan neck deformity is seen in advanced RA with damage to the ligaments and joints. Classically, there is distal interphalangeal (DIP) hyperflexion with proximal interphalangeal (PIP) hyperextension. Boutonniere deformity is similar, where there is PIP flexion with DIP hyperextension. These deformities are no longer common, as most patients are treated with disease-modifying antirheumatic drugs (DMARDs) at an early stage.

Ulnar deviation, due to inflammation of the metacarpophalangeal (MCP) joints, causes the fingers to become dislocated. As the tendons pull on the dislocated joints, the fingers tend to drift toward the ulnar side.

Extra-articular manifestations seen in more severe disease include pleuritis, interstitial lung disease, pericarditis, and inflammatory eye disease.

Laboratory tests

Once a clinical diagnosis is made, several laboratory tests help to determine prognosis. Rheumatoid factor (RF) is positive in about 60% to 70% of patients with RA.[51] It is not required for diagnosis but is helpful if present. It should be tested at presentation and does not need to be repeated if positive. The higher the values, the worse the prognosis and the greater the need for aggressive treatment. 

Anticyclic citrullinated peptide antibody (anti-CCP), a prognostic marker, is reported in about 70% of patients with RA.[52] Anti-CCP can be positive when RF is negative, and it seems to play more of a pathogenic role in the development of RA.[53] Anti-CCP does not need to be serially measured, even though it tends to decrease with better disease control.

Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) levels are also usually obtained because they reflect the level of inflammation. However, up to 40% of patients with RA may have normal levels.[54][55]

Imaging

Baseline radiographs of the hands and feet are obtained to help with diagnosis and in determining disease severity.[56] Patients with erosions at baseline who fulfill one of the classification criteria for RA are at risk for severe disease. If imaging the foot and ankle, avoid nonweight-bearing radiographs if the patient is able to stand. This is to ensure the most accurate assessment of the functional bony anatomy.​[57]​​

Ultrasound may complement x-ray in the evaluation of suspected RA; it may detect synovitis of the wrist and fingers at the initial presentation.[58][59]​ Ultrasound may add value in the diagnosis of early seronegative RA.[60] The presence of erosions, synovial hypertrophy, and hyperemia on ultrasound increases the post-test probability of inflammatory arthritis in seronegative patients.[61] It is not clear whether the addition of ultrasound to disease activity score strategies is of benefit.[62]​ UK guidelines do not currently recommend ultrasound for routine monitoring of disease activity in adults with RA.[63]

Do not order MRI as the initial imaging study to diagnose suspected RA because there is inadequate evidence to justify its use in clinical practice.​[64]​​[58][65]​​​​​ However, MRI can be used as an adjunctive imaging modality when there is diagnostic doubt.[58]​​

Disease activity scores

Determining disease activity and presence of poor prognostic factors at diagnosis (functional limitation, extra-articular disease, positive RF, positive anti-CCP, bony erosions on radiograph) should be used to support physician acumen to inform initial treatment decisions.

Composite disease measures are derived from the American College of Rheumatology (ACR) core data set, which includes:

  • Tender joint count

  • Swollen joint count

  • Functional status measured by a health assessment questionnaire (HAQ)

  • Multidimensional HAQ (MDHAQ) or its derivatives

  • Pain

  • Patient and physician global assessment of disease activity, and

  • Either an ESR or CRP as a marker of inflammation

Any three or more of these combined into a composite index can be used for disease activity monitoring. The most commonly used measures are the disease activity score (DAS), the 28-joint count version of DAS (DAS28), the simplified disease activity index (SDAI), the clinical disease activity index (CDAI), and routine assessment patient index data (RAPID3), all of which are recommended by the ACR.[66][67][68][69]

Each disease activity measure has its own thresholds of disease activity. For consistency, the same disease activity measure should be used throughout the patient's management. Studies have shown that with close monitoring of disease activity and treating to a target value, it is possible to achieve good responses with any DMARD or combination with biologic agents.[70][71][72]

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