Autoimmune Diagnostics

When autoimmune disease is suspected, a comprehensive history (taking of the patient’s medical history) and physical examination are followed by a step-by-step diagnostic procedure:

  • Basic internal medicine laboratory:
    • Small blood count
    • Differential blood count
    • Urine status including evidence of microalbuminuria (excretion of small amounts of albumin (20 to 200 mg/l or 30 to 300 mg per day) with urine, if applicable).
    • Inflammatory parameters – CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate) [if negative: manifest autoimmune disease unlikely].
    • Liver parameters – alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), gamma-glutamyl transferase (γ-GT, gamma-GT; GGT).
    • Renal parameters – urea, creatinine (if necessary, determination of creatinine clearance or cystatin C).
  • Basic rheumatology laboratory:
    • Inflammatory parameters – CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate).
    • Antinuclear antibodies (ANA) – In case of positive ANA screening (from ANA titer of 1:320 or, in case of suspected autoimmune disease, from a titer of 1:80), the following laboratory tests should be performed:
      • DsDNA antibody
      • ENA antibody

      Detection of dsDNA-AAK and ENA-AAK is highly specific for autoimmune disease!

    • Cyclic citrulline peptide antibodies (CCP-AK).
    • HLA-B27, if applicable
    • Rheumatoid factor [differential diagnostic relevance: > 50 U/ml; low titre RF levels are found in up to 10% of the healthy population].
  • Autoimmune diagnosis of diabetes mellitus.
    • Anti-glutamic acid decarboxylase antibody/anti-glutamic acid decarboxylase autoantibody (anti-GAD65-Ak).
    • Anti-tyrosine phosphatase antibody/autoantibody to protein tyrosine phosphatase IA 2 (IA-2-Ak), an islet cell antigen (anti-IA 2).
    • Autoantibodies against insulin (insulin-Ak (IgG); insulin autoantibodies (IAA)).
    • Islet cell antibodies (islet cell Ak; ICA-Ak).
    • Beta cell zinc transporter 8 (zinc transporter 8-Ak; ZnT8-Ak).
  • Further rheumatological diagnostics: see with the respective disease under laboratory diagnostics.