Initial Bloodwork for Autoimmune Disease Evaluation

First-Level Screening

The American College of Rheumatology recommends IIFA on HEp-2 cells as the reference method for ANA screening when evaluating for systemic autoimmune rheumatic diseases (SARD) 1, 2, 3
The screening dilution should be 1:160 on conventional HEp-2 substrates for adult populations, as this represents the 95th percentile of healthy controls 2, 4
Both the titer and pattern (nuclear, cytoplasmic, or mitotic) must be reported, as patterns provide critical diagnostic information 2, 5, 3
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 2, 3

A complete blood count with differential should be performed to detect cytopenias, anemia, or abnormal cells that may indicate disease activity or complications 6
A comprehensive metabolic panel including serum creatinine (or eGFR) and serum albumin should be performed to assess renal and hepatic function 6, 7
Inflammatory markers (ESR and C-reactive protein) should be assessed to evaluate acute phase response and disease activity 6, 7
Quantitative immunoglobulin levels (IgG, IgA, IgM) should be measured to identify immunodeficiency states 6

If ANA is positive, anti-dsDNA antibodies should be ordered when SLE is clinically suspected 2
A specific antibodies panel including anti-Ro, anti-La, anti-RNP, anti-Sm should be performed based on clinical presentation and ANA pattern 7, 2
Complement levels (C3, C4) are essential for SLE evaluation and monitoring 7, 2
Anti-phospholipid antibodies (lupus anticoagulant, anticardiolipin, anti-β2-glycoprotein I) should be measured if thrombosis, recurrent pregnancy loss, or thrombocytopenia is present 7

Urinalysis with urine protein/creatinine ratio should be performed to detect renal involvement 7
Infectious disease screening (HIV, hepatitis B and C) should be performed based on risk factors, especially before immunosuppressive therapy 6, 7
Tuberculosis screening should be performed according to local guidelines before immunosuppression 7

A negative ANA does not exclude autoimmune disease, as sensitivity is not 100% even at 1:160 dilution 4, 5
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 4, 3
Low-titer ANA can be clinically significant—titers above the screening threshold do not correlate with disease activity 4, 5
Do not use limited antigen panels (ELISA with restricted antigens) as initial ANA screening, as they miss important patterns and have lower sensitivity 2, 3
Bone marrow biopsy is only indicated for unexplained cytopenias or abnormal peripheral blood cells, not routine screening 6

No consensus exists for screening dilution in children under 16 years—some laboratories use 1:40 4, 3
Anti-Ro and anti-La antibodies should be checked before pregnancy due to risk of congenital heart block 7
Anti-phospholipid antibodies should be measured before pregnancy, surgery, transplant, or estrogen-containing treatments 7