Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX
For a patient presenting with a new rash and systemic symptoms suggestive of an autoimmune condition, the necessary investigations include:
- Blood tests for autoimmune markers: These may include rheumatoid factor and anti-cyclic citrullinated peptide (anti-CCP) antibodies if rheumatoid arthritis is suspected, especially if synovitis is present on clinical examination NICE NG100.
- Full blood count (FBC): To assess for cytopenias or other hematological abnormalities that may indicate systemic autoimmune or hematological disease NICE NG12.
- Inflammatory markers: Such as erythrocyte sedimentation rate (ESR) or plasma viscosity to evaluate systemic inflammation NICE NG12.
- Serological testing for specific infections that can mimic or trigger autoimmune conditions: For example, Lyme disease serology if there is a history or suspicion of tick exposure and compatible symptoms NICE NG95.
- Screening for associated autoimmune diseases: In cases like type 1 diabetes, screening for coeliac disease and thyroid disease may be appropriate NICE CKS,NICE CKS.
- Skin biopsy: May be considered if the rash is atypical or diagnosis is unclear, to help differentiate autoimmune from infectious or other causes (implied from clinical practice).
- Additional viral serologies: In pregnant patients or where viral exanthems are possible, testing for rubella, parvovirus B19, and measles immunity may be indicated NICE CKS,NICE CKS.
Referral to specialist care should not be delayed if autoimmune disease is strongly suspected, especially with persistent synovitis or systemic involvement NICE NG100.