Which laboratory tests are recommended for confirming a diagnosis of psoriatic arthritis in primary care?

In primary care, no specific laboratory test can definitively confirm a diagnosis of psoriatic arthritis. However, certain blood tests may be performed to support the clinical assessment and to exclude other conditions. These include inflammatory markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), although normal results do not rule out psoriatic arthritis. Testing for rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies may be considered to exclude rheumatoid arthritis, which can present similarly. Human leukocyte antigen B27 (HLA-B27) testing is not routinely used to confirm psoriatic arthritis but may be considered in cases with axial symptoms or when spondyloarthritis is suspected. Ultimately, diagnosis and confirmation require referral to secondary care for specialist assessment and further investigations, including imaging and validated classification criteria.

Summary of recommended laboratory tests in primary care:

• Inflammatory markers: CRP and ESR (normal levels do not exclude diagnosis)
• Rheumatoid factor and anti-CCP antibodies to exclude rheumatoid arthritis
• HLA-B27 testing may be considered if axial symptoms or spondyloarthritis suspected

Referral to rheumatology is essential for confirmation and management initiation.

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