Early diagnosis of RA is a prerequisite for early treatment and is not always easy to achieve. Diagnosis relies heavily on history taking and clinical examination and less on investigations.

The American College of Rheumatology (ACR; previously the American Rheumatism Association) criteria for the classification of RA¹⁶ illustrates this (see annex 2). The ACR criteria are, however, primarily a research tool and are much less useful in routine clinical practice.

2.1 Clinical features

A typical patient with early RA will describe pain, stiffness and swelling in the joints that is worse in the morning and after inactivity. Examination (see Table 1) reveals symmetrical swelling and tenderness of the small joints of the hands and feet (and to a variable extent the larger joints) and the presence of synovitis (i.e. soft tissue swelling in relation to the joint). Systemic 'flu-like' symptoms are not uncommon. Atypical presentations of RA include patients with mainly girdle joint involvement mimicking polymyalgia rheumatica and those with persistent monoarthritis.

Table 1

Assessing a patient presenting with inflammatory arthritis

These findings are not, however, exclusive to RA and may occur in a number of other inflammatory arthropathies. In early disease, therefore, differential diagnosis should always be considered (see Table 2).

Table 2

Differential diagnosis of early ra

• Viral arthritis (e.g. parvovirus, rubella)
• Reactive arthritis (e.g. post-infective: throat, gut, sexually acquired)
• Seronegative spondyloarthropathy (e.g. psoriatic, ankylosing spondylitis, inflammatory bowel disease)
• Connective tissue disease (e.g. systemic lupus erythematosus (SLE), scleroderma)
• Polymyalgia rheumatica
• Polyarticular gout
• Fibromyalgia
• Medical conditions presenting with arthropathy (e.g. sarcoidosis, thyroid disease, infective endocarditis, haemochromatosis, diabetic cheiroarthropathy, paraneoplastic syndromes, multiple myeloma).

2.2 Investigation

There is no single diagnostic test for RA. Investigations are used largely to support the clinical diagnosis and negative results do not exclude the diagnosis of RA. Investigations which may be helpful in making the diagnosis of early RA are shown in Table 3.

Table 3

Investigations helpful in diagnosis of ra

2.3 Prognostic features in early ra

Predicting outcome in RA in individual patients at disease outset is difficult. Improved understanding of prognostic features would help to identify patients with serious disease who require aggressive therapy and protect those with mild disease from exposure to potentially toxic treatment. Indicators of poor outcome (radiological, functional, mortality) are:

• Many active joints^{18, 19, 20}
• High ESR or CRP at outset^{12, 21, 22, 23}
• Positive rheumatoid factor^{19, 24, 25, 26}
• Early radiological erosions²⁷
• Poorer scores of function (e.g. HAQ) at outset^{18,19, 28, 29}
• Adverse socio-economic circumstances and lower educational level.^{30, 31, 32, 33, 34}