A Closer Look at Autoimmune Diagnostics
By Dr. Jane B. Ayala, FACR and Dr. Thomas A. Rennie, FACR Board Certified in Internal Medicine and Rheumatology
When you see a rheumatologist, they will almost certainly order tests – not just to confirm a diagnosis, but to understand how your immune system is behaving and whether organs are affected. Rheumatology relies heavily on pattern recognition, and tests provide the essential clues.
While no single test definitively diagnoses most autoimmune diseases, together, these tools help rheumatologists map out the nature and severity of a patient’s condition.
Let’s go through the most common tests and what each reveals.
FOUNDATIONAL BLOOD TESTS & ANALYSES
Anti-nuclear antibody (ANA)
- Screens for autoantibodies targeting the nucleus of cells.
- A general indicator of autoimmune activity, but can be seen in up to 15% of normal individuals.
C-reactive protein (CRP)
- Measures an acute-phase protein from the liver.
- Elevated levels signal active inflammation in the body.
Erythrocyte sedimentation rate (ESR)
- Measures how quickly red blood cells settle in a test tube.
- An elevated ESR may indicate systemic inflammation
Complement levels (C3 and C4)
- These proteins are part of your immune defense.
- Low levels suggest active immune complex disease, such as lupu
Creatine kinase (CK)
- Measures muscle enzyme levels.
- Elevated CK can indicate muscle inflammation or damage, like in myositis.
SPECIFIC AUTOANTIBODY TESTS
These tests look for highly specific antibodies, which help pinpoint the exact autoimmune disease at play. These tests may include:
Anti-double-stranded DNA (anti-dsDNA)
- Strongly associated with systemic lupus erythematosus (SLE).
Anti-Smith antibody (anti-Sm)
- A highly specific marker for lupus.
Anti-ribonucleoprotein antibody (anti-RNP)
- Seen in mixed connective tissue disease and lupus.
Anti-Sm/RNP antibody
- Detects both Sm and RNP antibodies, helping differentiate overlapping autoimmune diseases.
Anti-Sjögren’s-syndrome-related antigen A (anti-SSA / anti-Ro)
- Associated with Sjögren’s syndrome and lupus.
- Linked to dry eyes, dry mouth, and skin rashes.
Anti-Sjögren’s-syndrome-related antigen B (anti-SSB / anti-La)
- Also linked to Sjögren’s syndrome.
- Often found alongside anti-SSA antibodies.
Rheumatoid factor (RF)
- An antibody commonly elevated in rheumatoid arthritis.
Anti-cyclic citrullinated peptide antibody (anti-CCP)
- Highly specific for rheumatoid arthritis and useful for predicting disease progression.
Anti-neutrophil cytoplasmic antibodies (ANCA)
- Associated with vasculitis and inflammatory vascular diseases.
URINE TESTS
Urinalysis
- A urinalysis may be performed in order to check for protein in the urine, which can be seen with lupus and other autoimmune diseases.
IMAGING TESTS
In addition to lab tests, your rheumatologist may order:
- X-rays to view joint damage.
- Ultrasound to detect joint inflammation.
- MRI for detailed images of soft tissues and joints.
These imaging tools help detect early structural changes even before physical symptoms worsen.
WHY SO MANY TESTS?
Autoimmune diseases often present with a variety of non-specific symptoms – joint pain, fatigue, rashes – and no single test can always tell the whole story. Rheumatologists use this broad testing approach to answer three main questions:
1. Is the immune system activated inappropriately? Tests like ANA, CRP, ESR, CK, and complement levels provide that insight.
2. What type of autoimmune process is occurring? Specific autoantibodies help narrow down the diagnosis.
3. Is there organ involvement or risk of damage? Tests like urinalysis, complement levels, and CK help detect complications.
Think of these tests as pieces of a puzzle. One by one, they help the rheumatologist see the full picture and tailor a treatment plan specific to your condition.
YOUR ROLE AS A PATIENT
Understanding these tests can empower you to ask informed questions during your appointment, and help you feel more comfortable discussing your situation and concerns with your rheumatologist.
- Why is this test being ordered?
- What do the results mean for my condition?
- Will these results change my treatment plan?
Always feel free to engage in open conversation with your rheumatologist – it’s your health, and knowledge is your best tool.
Note: This content is for educational purposes only and does not constitute, nor should it be taken as personal medical advice. Rheum Relief is not intended to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare provider for medical guidance.