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Blood Test Tracker

ANA Pattern (ICAP)

Describes how the antibodies in a positive ANA test look under a microscope, such as smooth, speckled or dotted. The pattern helps guide which tests come next.

AI-verified against cited sources. Awaiting expert reviewAlso called ICAP pattern, HEp-2 IIFA pattern, AC patternLOINC 13068-2

What it is

When an ANA test is positive, the lab looks at how the glowing antibodies appear on a slide of human cells (HEp-2 cells). The glow can look smooth, speckled, dotted or ring-like, and it can sit in the center of the cell (the nucleus), in the small structures inside it (the nucleoli), in the cell fluid (the cytoplasm) or on the machinery that divides cells. Labs name these patterns, and many now use international codes from AC-1 to AC-29, set by a group called ICAP. More than one pattern can show up in the same sample.

Why it matters

The pattern gives your clinician a clue about which specific antibodies to look for next. For example, the centromere pattern (AC-3) is linked to limited systemic sclerosis, and the smooth, even glow (AC-1) is linked to antibodies against DNA and histones. A pattern cannot say what is going on by itself. Some patterns are also common in people with no autoimmune disease, such as the dense fine speckled pattern (AC-2). So the pattern is read together with the titer, your symptoms and any follow-up tests.

What can affect your result

  • Titer: low-titer patterns are common in people with no autoimmune disease
  • Lab method: slide brand, screening dilution and the reader's experience
  • Sex and age: positive ANA results are more common in women and in older people
  • Medicines and infections, which can cause a positive ANA
  • More than one pattern in the same sample, which some labs report separately with their own titers
  • The pattern is read by a trained person looking at a slide, so the same glow can be named differently from one lab to another.
  • Slides, screening dilutions and reading practices differ between labs. In a classic study, 15 labs each used their own in-house method on the same coded samples.
  • Some medicines and recent infections can cause a positive ANA. Tell your clinician about everything you take (MedlinePlus).

The pattern reflects the antibodies in your blood on the day of the draw. Whether it changes over time depends on the cause, so your clinician decides if a repeat is useful.

When to talk to a clinician

A pattern on its own is not urgent. Talk with the clinician who ordered the test about what it means with your symptoms and other results. Contact a clinician soon if you have new symptoms such as fever, a new rash, or joint pain, stiffness and swelling, and call your local emergency number for chest pain or trouble breathing.

Questions you could ask

  • Which pattern was seen, and what follow-up antibody tests does it suggest?
  • Was more than one pattern or titer reported?
  • How does this pattern fit with my symptoms?

Questions people ask

What do codes like AC-1 or AC-4 mean?

They are international codes from ICAP that give each ANA staining pattern a standard name. For example, AC-1 is homogeneous, AC-3 is centromere and AC-4 is fine speckled. Using the same codes helps labs and clinicians describe the same glow in the same way.

Can I have more than one pattern?

Yes. Some samples show two or more patterns. Quest reports every pattern it sees with its own titer. The patterns may point to the same condition, to two different ones, or to neither, particularly when the titer is low.

Does my pattern tell me which disease I have?

No. A pattern suggests which specific antibody tests may be worth doing next. The same pattern can be seen in different conditions, and some patterns are seen in healthy people. Your clinician reads it together with the titer, your symptoms and other results.

Show the science and sources

For clinicians and researchers

ICAP (the International Consensus on ANA Patterns) defines a standard nomenclature for HEp-2 indirect immunofluorescence (IIFA): AC-0 is negative, the nuclear patterns are AC-1 to AC-14 and AC-29, the cytoplasmic patterns are AC-15 to AC-23, and the mitotic patterns are AC-24 to AC-28 (Chan 2015, Damoiseaux 2019). Patterns are grouped into competent-level patterns that every reporting lab should recognize and expert-level patterns for specialist labs. The ICAP board advocates reporting the pattern, including cytoplasmic and mitotic patterns, instead of a simple ANA-positive label. Its clinical relevance statements are a consensus and not a systematic review (Damoiseaux 2019). Examples: AC-1 is linked to antibodies against dsDNA, nucleosomes and histones, and in the 2015 table to SLE, drug-induced lupus and juvenile idiopathic arthritis. AC-3 (centromere) is strongly associated with CENP-B antibodies and limited cutaneous systemic sclerosis and is included in SSc classification criteria. AC-2 (dense fine speckled, DFS70) is common in apparently healthy people and has an inverse association with systemic autoimmune rheumatic disease only when anti-DFS70 is confirmed and no other ENA is present. AC-29 (Topo I-like) is highly specific for systemic sclerosis, in particular the diffuse cutaneous form. AC-21 (reticular/AMA) is common in primary biliary cholangitis. Pattern assignment is observer dependent. In NHANES 1999 to 2004, among ANA-positive people, cytoplasmic patterns were seen in 21.8% and nucleolar patterns in 6.1%, and many people had more than one pattern (Satoh 2012). Mayo's result list includes a first and a second pattern, each with its own titer, plus a cytoplasmic pattern field, and Quest reports every pattern it sees with its own titer. LOINC 13068-2 is the generic IFA pattern code, and Mayo reports pattern results under 49311-4.

LOINC 13068-2 (primary), 49311-4, 14611-8, 49310-6. Specimen: serum.

Sources

  1. Report of the First International Consensus on Standardized Nomenclature of Antinuclear Antibody HEp-2 Cell Patterns 2014-2015, Frontiers in Immunology (2015)
  2. Clinical relevance of HEp-2 indirect immunofluorescent patterns: the International Consensus on ANA patterns (ICAP) perspective, Annals of the Rheumatic Diseases (2019)
  3. Tests for Autoimmune Diseases (ANA), Test FAQ 177, Quest Diagnostics
  4. Antinuclear Antibodies, HEp-2 Substrate, IgG, Serum (test NAIFA), Mayo Clinic Laboratories
  5. Prevalence and sociodemographic correlates of antinuclear antibodies in the United States, Arthritis & Rheumatism (2012)
  6. Range of antinuclear antibodies in healthy individuals, Arthritis & Rheumatism (1997)
  7. ANA (Antinuclear Antibody) Test, MedlinePlus, National Library of Medicine
  8. LOINC codes verified with the NLM Clinical Tables LOINC search (e.g. 13068-2), U.S. National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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