What this test measures
The ANA-17 Blot is a line immunoassay (LIA) or immunoblot that simultaneously tests for autoantibodies against approximately 17 nuclear and cytoplasmic antigens on a single test strip. The exact panel varies by manufacturer but typically includes: dsDNA, nucleosomes, histones, Smith (Sm), U1-RNP, Ro-52, SSA/Ro-60, SSB/La, centromere B, Scl-70 (topoisomerase I), PM-Scl, Jo-1, Mi-2, Ku, PCNA, ribosomal P, and AMA-M2.
Each antibody appears as a coloured band on the strip, and the intensity is graded by automated scanner. Results are reported as negative, weak, moderate or strong positive for each antigen.
Why it matters
When a screening ANA is positive (especially at high titre or with a specific pattern), the next step is to identify which specific antibody is responsible. The 17-blot panel does this efficiently — replacing what used to require multiple separate tests. The pattern of antibodies identified often clinches the diagnosis of a specific connective tissue disease:
Anti-dsDNA + anti-Sm = SLE; anti-Ro/anti-La = Sjögren or SLE; anti-U1-RNP = MCTD; anti-Scl-70 = diffuse scleroderma; anti-centromere = limited scleroderma (CREST); anti-Jo-1 / anti-Mi-2 = polymyositis/dermatomyositis; anti-PM-Scl = scleroderma-myositis overlap; anti-ribosomal P = lupus with neuropsychiatric features; AMA-M2 = primary biliary cholangitis. For Indian rheumatology and immunology practice, this single test substantially shortens the diagnostic workup.
How to prepare
No fasting required. Continue all medications including immunosuppressants — antibody levels remain stable on treatment. Tell your doctor about any biologic agents and recent infections for context.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Anti-Sm (Smith) (Qualitative)[1] | Negative | Negative. | Highly specific (~99%) for SLE; sensitivity ~25%. Often co-occurs with anti-U1-RNP. |
| Anti-U1-RNP (Qualitative) | Negative | Negative. | High titre = defining marker of mixed connective tissue disease (MCTD); lower titre seen in SLE. |
| Anti-Ro/SSA (52 + 60) (Qualitative) | Negative | Negative. | Sjögren syndrome (~70%), SLE (~30%), neonatal lupus / congenital heart block (when mother is positive in pregnancy). Anti-Ro-52 alone also seen in myositis, scleroderma. |
| Anti-Scl-70 (Qualitative) | Negative | Negative. | Diffuse systemic sclerosis; predicts lung involvement. |
| Anti-Centromere (Qualitative) | Negative | Negative. | Limited cutaneous scleroderma (CREST); predicts pulmonary hypertension over years. |
| Anti-Jo-1 (Qualitative) | Negative | Negative. | Polymyositis / dermatomyositis with anti-synthetase syndrome (ILD, mechanic's hands, arthritis). |
Common 17-blot patterns → disease
| Positive bands | Likely diagnosis |
|---|---|
| dsDNA + Sm + Ro + La | SLE |
| U1-RNP high titre | MCTD |
| Ro + La (no dsDNA) | Sjögren syndrome |
| Scl-70 | Diffuse systemic sclerosis |
| Centromere B | Limited scleroderma (CREST) |
| Jo-1 + Ro-52 | Anti-synthetase syndrome (myositis + ILD) |
| PM-Scl | Polymyositis/scleroderma overlap |
| Ribosomal P | Lupus with neuropsychiatric / hepatic features |
| AMA-M2 | Primary biliary cholangitis |
Frequently asked questions
Why is this panel done instead of separate tests?
It is faster and cheaper than ordering each antibody separately and gives a complete picture for diagnosing connective tissue disease.
Do I need to fast?
No fasting required.
My panel shows only one weak positive — what does it mean?
Weak isolated positives can be non-specific or transient. Your rheumatologist will interpret in context with symptoms, ANA-IFA titre and other tests.
Should this replace ANA-IFA?
No. ANA-IFA is the gold-standard screen. The 17-blot is run after a positive ANA to identify the specific antibody.
Will the result change with treatment?
Most antibodies remain detectable for years even with effective treatment. Doctors monitor disease activity by clinical scores, not by repeating this panel.
How long is the report?
Typically 3–5 days.
Is this the same as "ENA panel"?
ENA (extractable nuclear antigens) is similar but typically smaller (6–8 antigens). 17-blot is an expanded version with additional antibodies useful in myositis, scleroderma and overlap syndromes.
Related Toxicology / Trace Elements tests
Tests commonly ordered alongside ANTINUCLEAR ANTIBODIES-17 BLOT, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — ANA Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Connective Tissue Diseases · accessed 2026-05-30T00:00:00.000Z
- ACR — Connective Tissue Disease Position Statements · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — ENA Panel · accessed 2026-05-30T00:00:00.000Z
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