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[Immunology](https://durgical.com/en/immunology/) · [Immunology lab](https://durgical.com/en/immunology/#a-lab)

# Immunofluorescence and the ANA test

- Topic

The ANA test looks for antibodies against the nucleus of the body's own cells. It is read with a fluorescence microscope and points toward autoimmune disease.

Updated 2026-11-01

## Key points

- ANA: sensitive for lupus; anti-dsDNA and anti-Sm: specific.
- Anti-histone = drug-induced lupus.
- Anti-centromere = CREST; anti-Scl-70 = diffuse systemic sclerosis.
- Direct IF on biopsy: linear (anti-GBM) versus granular (immune complexes).
- Low-titer ANA is common in healthy people.

## What it is

In immunofluorescence, an antibody tagged with a fluorescent dye shows where antibodies bind. For antinuclear antibodies (ANA), serum is incubated on HEp-2 cells and the titer and nuclear staining pattern are reported. A negative ANA makes lupus very unlikely, but a positive ANA alone diagnoses nothing.

## Key facts

- ANA is very sensitive for lupus (positive in almost all) but not specific.
- The most lupus-specific antibodies are anti-double-stranded DNA and anti-Sm.
- Low titers occur in healthy people, especially older women, and in viral infections.
- Some drugs (procainamide, hydralazine, isoniazid) induce ANA and anti-histone antibodies.

## ANA patterns and classic associations

| Pattern | Typical antibodies | Association |
| --- | --- | --- |
| Homogeneous | Anti-double-stranded DNA, anti-histone | Lupus; drug-induced lupus (anti-histone) |
| Speckled | Anti-Sm, anti-RNP, anti-Ro, anti-La | Lupus, mixed connective tissue disease, Sjögren |
| Centromere | Anti-centromere | Limited systemic sclerosis (CREST) |
| Nucleolar | Anti-Scl-70 or other nucleolar antibodies | Diffuse systemic sclerosis |

## In the lab

- Indirect immunofluorescence: patient serum + reference cells or tissue + fluorescent anti-immunoglobulin. Used for ANA and ANCA.
- Direct immunofluorescence: patient biopsy + fluorescent anti-immunoglobulin; in kidney and skin it shows where deposits sit.
- Linear pattern (anti-glomerular basement membrane, pemphigoid) versus granular (immune complexes, as in lupus nephritis).
- The titer is reported as a dilution (1:80, 1:160…); many labs take 1:160 or higher as significant.

## Memory aid

ANA is the doorbell: if it does not ring, lupus is almost surely not home; if it rings, you still open the door with anti-dsDNA and anti-Sm.

## Test yourself

Think of the answer, then tap the question to see it.

## Which two autoantibodies are most specific for systemic lupus erythematosus?

Anti-double-stranded DNA and anti-Sm.

## Which antibody suggests drug-induced lupus?

Anti-histone antibodies, with a homogeneous ANA pattern.

## Which ANA pattern goes with limited systemic sclerosis (CREST)?

The centromere pattern, from anti-centromere antibodies.

## What is the difference between direct and indirect immunofluorescence?

Direct looks for antibodies already deposited in the patient's tissue; indirect looks for antibodies in the patient's serum on reference cells or tissue.

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## Related

- [Serology: IgM vs IgG, seroconversion, avidity](https://durgical.com/en/immunology/serology-igm-vs-igg-seroconversion-avidity/)
- [Direct and indirect Coombs test](https://durgical.com/en/immunology/direct-and-indirect-coombs-test/)
- [Flow cytometry and the CD4 count](https://durgical.com/en/immunology/flow-cytometry-and-the-cd4-count/)
- [Autoantibodies: the table to know](https://durgical.com/en/immunology/autoantibodies-the-table-to-know/)
- [Type III hypersensitivity (immune complexes)](https://durgical.com/en/immunology/type-iii-hypersensitivity/)

## Related conditions

- [Systemic lupus erythematosus](https://durgical.com/en/conditions/systemic-lupus-erythematosus/)
- [Rheumatoid arthritis](https://durgical.com/en/conditions/rheumatoid-arthritis/)

[← All of immunology](https://durgical.com/en/immunology/)

Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given.

Sources: [ANA (Antinuclear Antibody) Test](https://medlineplus.gov/lab-tests/ana-antinuclear-antibody-test/) (MedlinePlus (U.S. National Library of Medicine), 2024); [Antinuclear antibody panel](https://medlineplus.gov/ency/article/003535.htm) (MedlinePlus (U.S. National Library of Medicine), 2024).

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