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Investigations for musculoskeletal pain

Back to Widespread musculoskeletal pain

You can generally decide whether to refer a patient onto a specialist based on the patient's history and your examination. But investigations in widespread musculoskeletal pain can be most useful to:

  • maximise the benefit of the patient's first outpatient appointment – your local clinical pathways may determine which tests you can use to help get access to a specialist opinion
  • add certainty to a case that you think is non-inflammatory or manageable in primary care.

However, no investigation will exclude an inflammatory arthritis and all investigations can give false positives.

Erythrocyte sedimentation rate (ESR)/C-reactive protein (CRP)

ESR/CRP tests can help to distinguish inflammatory from other joint conditions but they're not very sensitive and are very non-specific. A normal ESR doesn't rule out inflammatory arthritis.

Rheumatoid factor

Rheumatoid factor tests can also be positive in the normal population (c. 5% prevalence, higher in the elderly) especially at low titre (for example <23 units/ml).

It'll be positive in around 70% of patients with rheumatoid arthritis and >90% of patients with primary Sjögren's syndrome.

Just as a normal ESR may be seen in rheumatoid arthritis, a negative rheumatoid factor doesn't rule out rheumatoid arthritis.

Antinuclear factor (ANF)

Low-titre ANF (titres of ≤1:80) may be clinically insignificant. Higher titres may be seen in various conditions, including rheumatoid arthritis and connective tissue diseases, and sometimes in viral and chronic infections.

Anti-citrullinated protein antibodies (ACPA)

Anti-citrullinated protein antibodies (ACPA) is also known as anti-cyclic citrullinated peptide (anti-CCP).

APCA-positivity is more specific than rheumatoid factor for rheumatoid arthritis, but it has relatively low sensitivity and so patients with rheumatoid arthritis may be ACPA-negative.

ACPA testing isn't currently recommended in primary care.


X-rays tend to be of limited usefulness, particularly in the early stages of disease. In rheumatoid arthritis it may take up to two years before x-rays show erosive changes in the joints so they're not essential in deciding whether or not to refer a patient. If you do see erosive changes in a patient's x-rays they should be referred urgently.

You can generally diagnose osteoarthritis clinically but x-rays may be useful when considering other pathologies or sometimes prior to referral for joint replacement surgery.

Joint aspiration

Joint aspiration can be helpful diagnostically, particularly if you think the patient has a crystal arthritis.

Acute synovitis in a single joint needs urgent aspiration to rule out septic arthritis. Depending on local pathways, referral might be to Orthopaedics, A&E or Rheumatology.

Kim's investigations

Blood tests and imaging may be helpful in confirming Kim's diagnosis or ruling out other conditions but it's important to be aware of their limitations.

Fahmida's investigations

From Fahmida's history you might suspect she has fibromyalgia. Investigations are of limited use in ‘ruling in’ fibromyalgia, but may be helpful in excluding other diagnoses.

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Back to Widespread musculoskeletal pain

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