Diagnosis and investigations

Early diagnosis is required for appropriate early treatment to control symptoms and delay disease progression. However, it is not always easy. There is no single diagnostic test for RA, and diagnosis relies heavily on history taking and clinical examination and less on investigations.

• examination finding include:
  • swelling of three or more joints – specificity of 73%
  • tenderness largely along the joint line
  • synovitis – producing a “boggy” or “doughy” swelling which may ne subtle
  • a positive “squeeze” test
    • pain on gently squeezing the metacarpophalangeal or metatarsophalangeal joints together (sensitivity 40-48% but specificity 84% for early disease) (1).

Investigations include:

• ESR and CRP
  • usually increased
  • it is useful measure periodically in the assessment of the disease activity, thus may be used to monitor disease course
• presence of rheumatoid factor
  • 69% sensitive and 85% specific
  • high sero-positivity tends to be associated with systemic complications (nodules, vasculitis, neuropathy) - but may occur in other conditions; see option from the menu below
• anti-CCP antibodies
  • consider if rheumatoid factor is negative
  • has similar sensitivity to rheumatoid factor (67%) but is more specific (95%)
• anticitrulline antibody - associated with erosive RA
• other blood tests:
  • FBC (anaemia)
  • low albumin level
  • hypergammaglobulinaemia
  • increased fibrinogen level
  • circulating complement level – normal or elevated
• urinanalysis
  • microscopic hematuria, leukocyturia or proteinuria may be present in SLE (4)
• joint aspiration
• ultrasonography - may be more sensitive for early synovitis, but its availability is limited in the UK.
• radiology
  • X-ray the hands and feet early in the course of the disease in people with persistent synovitis in these joints
  • changes seen on x-ray include: soft tissue oedema, osteopenia, joint space narrowing, erosion, sunchondral cysts (2,3)

NICE states with respect to investigations for diagnosis:

• offer to carry out a blood test for rheumatoid factor in adults with suspected rheumatoid arthritis (RA) who are found to have synovitis on clinical examination
• consider measuring anti-CCP antibodies in adults with suspected RA if they are negative for rheumatoid factor
• X-ray the hands and feet in adults with suspected RA and persistent synovitis Investigations following diagnosis
  • soon as possible after establishing a diagnosis of RA: If anti-CCP antibodies are present or there are erosions on X-ray:
    • measure anti-CCP antibodies, unless already measured to inform diagnosis
    • X-ray the hands and feet to establish whether erosions are present, unless X-rays were performed to inform diagnosis
    • measure functional ability using, for example, the Health Assessment Questionnaire (HAQ), to provide a baseline for assessing the functional response to treatment
      
      
    • advise the person that they have an increased risk of radiological progression but not necessarily an increased risk of poor function, and
    • emphasise the importance of monitoring their condition, and seeking rapid access to specialist care if disease worsens or they have a flare

NICE suggest that primary clinicians should:

• refer for specialist opinion any person with suspected persistent synovitis of undetermined cause
• refer urgently if any of the following apply:
  • the small joints of the hands or feet are affected
  • more than one joint is affected
  • there has been a delay of 3 months or longer between onset of symptoms and seeking medical advice
• do not avoid referring urgently any person with suspected persistent synovitis of undetermined cause whose blood tests show a normal acute-phase response or negative rheumatoid factor (3)

The European League Against Rheumatism (EULAR) recommends that

• patients presenting with arthritis (any joint swelling, associated with pain or stiffness) should be referred to, and seen by, a rheumatologist, within 6 weeks after the onset of symptoms
• clinical examination is the method of choice for detecting arthritis, which may be confirmed by ultrasonography (US) (4).

Reference:

1. Harnden K, Pease C, Jackson A. Rheumatoid arthritis. BMJ. 2016;352:i387.
2. Amaya-Amaya J, Rojas-Villarraga A, Mantilla RD, et al. Rheumatoid arthritis. In: Anaya JM, Shoenfeld Y, Rojas-Villarraga A, et al., editors. Autoimmunity: From Bench to Bedside [Internet]. Bogota (Colombia): El Rosario University Press; 2013 Jul 18. Chapter 24.
3. National Institute for Health and Care Excellence (NICE) 2018. Rheumatoid arthritis in adults: management
4. Combe B et al. 2016 update of the EULAR recommendations for the management of early arthritis. Ann Rheum Dis. 2017;76(6):948-959.