What bloodwork is recommended for the initial evaluation of autoimmune disease?

Initial Bloodwork for Autoimmune Disease Evaluation

For initial evaluation of suspected autoimmune disease, start with ANA testing by indirect immunofluorescence assay (IIFA) as the first-level screening test, followed by a comprehensive panel including complete blood count, comprehensive metabolic panel, inflammatory markers (ESR and CRP), complement levels (C3, C4), and quantitative immunoglobulin levels. 1

First-Level Screening

Anti-Nuclear Antibody (ANA) Testing

• IIFA on HEp-2 cells is the reference method for ANA screening and should be performed first when evaluating for systemic autoimmune rheumatic diseases (SARD) 1, 2
• The screening dilution should be 1:160 on conventional HEp-2 substrates for adult populations, as this represents the 95th percentile of healthy controls 1
• Both the titer and pattern (nuclear, cytoplasmic, or mitotic) must be reported, as patterns provide critical diagnostic information 1, 2
• If alternative automated methods (ELISA, multiplex assays) are used and negative, but clinical suspicion remains high, IIFA must be performed due to superior sensitivity for SLE and systemic sclerosis 1, 2

Core Laboratory Panel

• Complete blood count with differential to detect cytopenias, anemia, or abnormal cells that may indicate disease activity or complications 1, 3
• Comprehensive metabolic panel including serum creatinine (or eGFR) and serum albumin to assess renal and hepatic function 1
• Inflammatory markers: ESR and C-reactive protein to assess acute phase response and disease activity 1, 4
• Quantitative immunoglobulin levels (IgG, IgA, IgM) to identify immunodeficiency states 1

Reflex Testing Based on ANA Results

If ANA is Positive

• Anti-dsDNA antibodies should be ordered when SLE is clinically suspected 1
• Specific antibodies panel including anti-Ro, anti-La, anti-RNP, anti-Sm based on clinical presentation and ANA pattern 1
• Complement levels (C3, C4) are essential for SLE evaluation and monitoring 1
• Anti-phospholipid antibodies (lupus anticoagulant, anticardiolipin, anti-β2-glycoprotein I) if thrombosis, recurrent pregnancy loss, or thrombocytopenia is present 1

Pattern-Directed Testing

• Cytoplasmic patterns warrant specific antibody testing for conditions like rheumatoid arthritis or myositis 1, 2
• Nucleolar patterns suggest systemic sclerosis and should prompt anti-Scl-70 or anti-centromere antibody testing 2

Additional Baseline Testing

Screening for Associated Conditions

• Rheumatoid factor and anti-CCP antibodies if inflammatory arthritis is suspected, though 30-40% of RA patients may be seronegative 5
• Urinalysis with urine protein/creatinine ratio to detect renal involvement 1
• Infectious disease screening: HIV, hepatitis B and C based on risk factors, especially before immunosuppressive therapy 1
• Tuberculosis screening according to local guidelines before immunosuppression 1

Critical Pitfalls to Avoid

Interpretation Errors

• A negative ANA does not exclude autoimmune disease, as sensitivity is not 100% even at 1:160 dilution 1
• ANA positivity occurs in up to 31.7% of healthy individuals at 1:40 dilution and 5% at 1:160, so clinical context is essential 1, 2
• Low-titer ANA can be clinically significant—titers above the screening threshold do not correlate with disease activity 1
• Autoantibody positivity alone does not make a diagnosis, and absence does not exclude it 6, 3

Testing Strategy Errors

• Do not use limited antigen panels (ELISA with restricted antigens) as initial ANA screening, as they miss important patterns and have lower sensitivity 1, 2
• Do not order extensive autoantibody panels without clinical indication—this leads to false positives and unnecessary patient anxiety 6
• Bone marrow biopsy is only indicated for unexplained cytopenias or abnormal peripheral blood cells, not routine screening 1

Special Populations

Pediatric Considerations

• No consensus exists for screening dilution in children under 16 years—some laboratories use 1:40 1, 2
• The same core panel applies, with particular attention to hereditary periodic fever syndromes if recurrent fevers are present 4

Pre-Treatment Evaluation

• Anti-Ro and anti-La antibodies should be checked before pregnancy due to risk of congenital heart block 1
• Anti-phospholipid antibodies before pregnancy, surgery, transplant, or estrogen-containing treatments 1