• Suspect rheumatoid arthritis (RA) in anyone with persistent synovitis, where no other underlying cause is obvious (for example, psoriatic arthritis).
• Clinical judgement should be used to decide if the synovitis is 'persistent' (lasting a few weeks rather than days).
• RA typically causes symmetrical joint synovitis of the small joints of the hands and feet, although any synovial joint may be affected. Clinical features of synovitis include:
• Pain — usually this is worse at rest or during periods of inactivity.
• Swelling — around the joint (not bone swelling).
• Stiffness and loss of function — stiffness is common in the morning and with inactivity, and usually lasts more than 30 minutes.
• A tender and warm joint — giving a 'boggy' feel on palpation.
• In addition to joint synovitis, RA may present with:
• A family history of RA (although concordance rates in monozygotic twins are only 15%).
• Rheumatoid nodules — hard, firm swellings over extensor surfaces occur in a third of people with RA.
• Extra-articular features such as lymphadenopathy, or involvement of other body systems (for example, eye, lungs, and heart).
• Systemic features of malaise, fatigue, fever, sweats, and weight loss.
• The presentation of RA is variable.
• Most people have an insidious onset, but others can have a rapid, or relapsing and remitting course (such as a palindromic presentation).

This approach to suspecting rheumatoid arthritis (RA) is based on the National Institute for Health and Clinical Excellence (NICE) guideline Rheumatoid arthritis: national clinical guideline for management and treatment in adults [National Collaborating Centre for Chronic Conditions, 2009; NICE, 2009].

• NICE recommends that the most important clinical feature to detect a new presentation of RA is synovitis, and if the small joints of the hands and feet are involved, the primary healthcare professional should lower their threshold for suspecting RA.
• NICE recommends that a diagnosis of RA should be suspected in anyone with persistent synovitis. However, NICE does not provide guidance on how long the person should have synovitis before it is considered to be 'persistent'. Therefore, CKS recommends that clinical judgement be used to decide whether synovitis is persistent or not.
• NICE states that diagnosis of RA should be based on clinical findings. After reviewing good quality evidence (one cohort study and 12 case series), NICE concluded that the following clinical features help identify people who are likely to have persistent synovitis and go on to develop RA:
• A history of ever having experienced prolonged morning stiffness (and this is more helpful than currently having morning stiffness).
• Both swelling and tenderness in affected joints, particularly small joints.
• Involvement of proximal interphalangeal joints and metacarpophalangeal joints.
• Symmetrical joints are affected.
• A greater number of joints are affected.
• An inability to make a fist or flex fingers.
• A positive metacarpophalangeal squeeze test.
• The American College of Rheumatology (ACR) classification criteria for RA have been widely used for diagnosis [American College of Rheumatology, 1987]. However, NICE states that a diagnosis of RA should no longer be constrained by the ACR criteria.
• The ACR criteria are mainly used for research purposes. There is good quality evidence (one cohort study and 12 case series) to suggest the ACR criteria are not useful for discriminating between RA and other conditions presenting with synovitis.

• Other conditions that may cause synovitis include:
• Septic arthritis — suspect this if a single joint is hot and swollen, especially if there are signs of sepsis (such as fever).
• Viral arthritis — suspect this if the person has an ongoing infection (such as hepatitis, rubella, parvovirus).
• Reactive arthritis — suspect this if the person has recently had a sore throat, gastroenteritis, or sexually transmitted infection.
• Seronegative spondyloarthritis — suspect this if there is a history of psoriasis, back pain, or bowel problems.
• Polymyalgia rheumatica — suspect this if the main symptoms are shoulder pain and stiffness.
• Polyarticular gout — suspect this if the person has risk factors for gout, or visible tophi.
• Connective tissue disease — suspect this if there are signs of a butterfly rash or scleroderma, or there are symptoms of significant Raynaud's disease.
• Medical conditions such as sarcoidosis, thyroid disease, multiple myeloma, infective endocarditis, acute rheumatic fever, and haemochromatosis.

The causes of synovitis are taken from the Scottish Intercollegiate Guidelines Network (SIGN) guideline: Management of early rheumatoid arthritis [SIGN, 2000].

• Rheumatoid arthritis can be difficult to diagnose, as many other conditions may present with synovitis.

• There is no specific diagnostic test for rheumatoid arthritis (RA). All people suspected of having RA should be referred for specialist assessment.
• If RA is suspected clinically, investigations are not necessary in primary care. However consider the following tests to speed up the diagnostic process, and act as a baseline measure prior to treatment:
• Full blood count, and C-reactive protein or erythrocyte sedimentation rate.
• Urea and electrolytes, liver function tests, calcium, and bone profile.
• Rheumatoid factor.
• Auto-antibodies (such as antinuclear antibodies).
• Radiography of the hands and the feet — if synovitis is affecting these joints.
• Chest radiography — to exclude lung involvement (which is common in RA).
• Anti-cyclic citrullinated peptide antibodies — usually a discussion with a specialist is necessary, depending on local policy and availability.
• Anti-CCP antibodies should only be done if the person is known to be rheumatoid factor negative and likely to be started on combination treatment.
• Ultrasound or magnetic resonance imaging (MRI) of joints — depending on local policy and availability.
• Do not let investigations delay a referral for clinically suspected RA.

• Rheumatoid factor — is positive in 60–70% of people with rheumatoid arthritis (RA) but may also be positive in people with other inflammatory diseases and in those who are healthy. The presence or absence of rheumatoid factor does not exclude or confirm a diagnosis of RA.
• C-reactive protein or erythrocyte sedimentation rate — inflammatory markers are usually, but not always, elevated in RA.
• Full blood count — normochromic, normocytic anaemia and reactive thrombocytosis are common in active RA.
• Urea and electrolytes — most treatments for RA can affect renal function, therefore a baseline measure is useful prior to starting treatment.
• Liver function tests — mild elevations of alkaline phosphatase and gamma-glutamyltransferase are common in active RA.
• Antinuclear antibodies (ANA) — may suggest connective tissue diseases such as systemic lupus erythematosus (SLE). However, ANA is positive in up to 30% of people with RA who are also rheumatoid factor positive, and may be weakly positive in up to 10% of healthy people.

These recommendations are based on the National Institute for Health and Clinical Excellence (NICE) guideline Rheumatoid arthritis: national clinical guideline for management and treatment in adults [National Collaborating Centre for Chronic Conditions, 2009; NICE, 2009].

• The diagnosis of rheumatoid arthritis (RA) should be based on clinical findings. If RA is suspected, referral to a specialist is necessary to confirm the diagnosis as blood tests and radiography may be normal in the early stages of RA, particularly if synovitis is only affecting the small joints.
• A specialist will carry out tests to support or refute the diagnosis of RA, to gather information on prognosis, and to guide treatment. If investigations are started in primary care, the results will provide further information for the specialist, speeding up the diagnostic process.
• After reviewing good quality evidence (two meta-analyses, three case-controlled studies, and 12 case series), NICE concluded that rheumatoid factor, anti-cyclic citrullinated peptide (anti-CCP) antibodies, and erosions on hand radiographs are useful predictors for diagnosing RA. Elevated CRP is a poor predictor.
• At presentation, a positive rheumatoid factor test detects less than half the people who eventually develop RA.
• Inflammatory markers are no different in people presenting with inflammatory arthritis who eventually develop RA compared with those who do not.
• Testing for anti-CCP antibodies is only useful if the person is negative for rheumatoid factor. If both antibodies are positive, the person will have a poorer prognosis. However, there is no evidence that a person with a positive anti-CCP antibody should be treated any differently than a person who is positive for rheumatoid factor.
• After reviewing the evidence (one case series), NICE stated that ultrasound and magnetic resonance imaging (MRI) scans are superior to clinical examination in the detection of synovitis, and that they are more sensitive to the presence of erosions and other early inflammatory signs and damage than conventional radiography. However, the long-term significance of this, and their limited availability in primary care, currently limits their use in practice.
• After reviewing good quality evidence (33 case series), NICE concluded that the presence of rheumatoid factor, anti-CCP antibodies, rheumatoid nodules, elevated inflammatory markers, poor grip strength, and an increasing number of swollen joints, were useful indicators of a poor prognosis for RA.