Antinuclear Antibodies
ANA· also: Antinuclear Antibody, FANA
Clinical Overview
ANA (Antinuclear Antibodies) is a screening test for autoimmune diseases. A positive ANA result means the immune system is producing antibodies that attack the body's own cell nuclei. It is the first-line screening test for Systemic Lupus Erythematosus (SLE), Sjögren's syndrome, scleroderma, myositis, and mixed connective tissue disease.
Why This Test Matters
ANA is a sensitive but non-specific screening test — a positive result does not diagnose an autoimmune disease by itself. Approximately 5–15% of healthy individuals are ANA-positive at low titers (1:40), especially women and the elderly. The higher the titer and the more specific the pattern, the more clinically meaningful the result. A positive ANA should always be followed by specific antibody testing (anti-dsDNA for lupus, anti-Ro/La for Sjögren's, anti-Scl-70 for scleroderma, anti-Jo-1 for myositis). ANA is negative in fewer than 5% of confirmed SLE cases — making it a highly sensitive screening test for that condition.
Reference RangesWHO/IFCC standards
| Reference Range | Unit | Notes |
|---|---|---|
| < 1:1 | titer | Negative <1:40 titer; Positive ≥1:80 |
Also reported in: ratio.
What Causes Abnormal Results?
High ANA Causes
- Systemic Lupus Erythematosus (SLE) — nearly 100% sensitive
- Sjögren's syndrome
- Scleroderma (systemic sclerosis)
- Mixed connective tissue disease (MCTD)
- Polymyositis / dermatomyositis
- Drug-induced lupus (procainamide, hydralazine, isoniazid, minocycline)
- Rheumatoid arthritis (low titer positive)
- Chronic liver disease and hepatitis C
- Healthy individuals (low titer — 5–15% of general population)
Low ANA Causes
- A negative ANA makes SLE very unlikely (<5% of confirmed SLE are ANA negative)
Signs & Symptoms to Watch For
How to Prepare for This Test
No special preparation required. ANA is a qualitative blood test — fasting is not necessary. Results are reported as titer (e.g., 1:40, 1:80, 1:160, 1:320) and pattern (homogeneous, speckled, nucleolar, centromere, peripheral).
Factors That Can Affect Results
- Age (ANA positivity increases with age — especially in women over 70)
- Gender (ANA more commonly positive in women)
- Medications — many drugs can cause drug-induced lupus with positive ANA
- Active infections (transient low-titer ANA can occur)
- Lab assay variation — ELISA vs. HEp-2 immunofluorescence gives different results
Related Topics
Frequently Asked Questions
I tested positive for ANA — do I have lupus?
Not necessarily. A positive ANA alone does not diagnose lupus. Approximately 5–15% of healthy people have a low-titer positive ANA without any autoimmune disease. Lupus diagnosis requires meeting at least 4 of 11 clinical and laboratory criteria (the ACR/EULAR criteria), which include organ involvement such as kidney disease, blood disorders, skin rash, and joint problems — in addition to specific antibodies like anti-dsDNA. If you are ANA positive, your doctor will review your symptoms and order more specific tests.
What do the ANA patterns mean?
The ANA immunofluorescence pattern suggests which antibody is present. Homogeneous (diffuse): most commonly seen in SLE, associated with anti-dsDNA and anti-histone. Speckled: the most common pattern — associated with anti-Sm, anti-RNP, anti-Ro, anti-La (SLE, Sjögren's, MCTD). Nucleolar: associated with anti-Scl-70 and anti-RNA polymerase (scleroderma). Centromere: associated with anti-CENP-B (limited scleroderma/CREST syndrome). Pattern alone is not diagnostic; specific antibody tests are required for confirmation.
Can medications cause a positive ANA?
Yes — drug-induced lupus is a well-recognized syndrome. Medications most commonly responsible include procainamide, hydralazine, isoniazid, minocycline, TNF-alpha inhibitors (etanercept, infliximab), chlorpromazine, and quinidine. Drug-induced lupus presents with joint pain, serositis, and positive ANA (typically anti-histone). Unlike true SLE, it resolves when the offending drug is stopped and rarely causes kidney or CNS involvement.