5th June 2025

Investigations

Initial investigations should include:

• Antinuclear antibody (ANA) – a positive ANA does not diagnose SLE, but a diagnosis of SLE requires a positive ANA
• Anti-Ro antibody – rarely, ANA can be negative in anti-Ro-antibody positive lupus
• Double-stranded DNA, Smith antigen – highly specific for SLE and often confirmatory of diagnosis if present
• Full blood count – often leukopenia caused by neutropenia, anaemia
• Clotting screen – activated partial thromboplastin time may be prolonged if antiphospholipid antibodies present
• Kidney function and urinalysis – deranged if renal system affected
• ESR and CRP – elevated due to systemic inflammation

Subsequent investigations which can be considered:

• Coombs’ test to assess for haemolysis
• Complement levels – often raised in SLE
• Antiphospholipid antibodies
• Skin or renal biopsy