What are the recommended initial investigations for a patient presenting with joint pain and swelling?

For a patient presenting with joint pain and swelling, the recommended initial investigations include:

• Clinical examination to identify synovitis and affected joints, especially small joints of hands or feet, which may indicate rheumatoid arthritis (RA) ¹.
• Blood tests such as rheumatoid factor (RF) in adults with suspected RA who have synovitis on examination ¹.
• Anti-cyclic citrullinated peptide (anti-CCP) antibodies measurement if rheumatoid factor is negative but RA is still suspected ¹.
• X-rays of hands and feet to detect erosions or persistent synovitis in suspected RA ¹.
• Serum urate level measurement if gout is suspected, especially with rapid onset of severe joint pain and swelling, to confirm diagnosis (serum urate ≥360 micromol/litre) ².
• Consider joint aspiration and synovial fluid microscopy if gout diagnosis remains uncertain or to exclude septic arthritis ².
• Imaging (X-ray, ultrasound, or dual-energy CT) may be considered if joint aspiration is not possible or diagnosis remains unclear ².
• For osteoarthritis, diagnosis is primarily clinical without routine imaging unless atypical features or alternative diagnoses are suspected ³.

Referral to a specialist should not be delayed by investigations if persistent synovitis of undetermined cause is present ¹.