Antinuclear Antibodies
Imunidade e inflamaçãoÚltima revisão: 7 de abril de 2026. Abordagem de fontes: contexto padrão de interpretação laboratorial, material médico de referência e orientações clínicas ou de saúde pública quando relevantes.
O que é Antinuclear Antibodies?
Antinuclear antibodies (ANA) are autoantibodies directed against various components of the cell nucleus, including DNA, histones, nucleolar proteins, centromeres, and other nuclear antigens. The ANA test is the most widely used screening test for systemic autoimmune diseases, particularly systemic lupus erythematosus (SLE). The standard testing method is indirect immunofluorescence (IIF) on HEp-2 cells, which allows visualization of the staining pattern—a critical piece of diagnostic information. Results are reported as a titer (e.g., 1:80, 1:160, 1:320) reflecting the highest dilution at which fluorescence is still detected, along with the pattern of nuclear staining.
The ANA staining pattern provides clues to the specific autoantibodies present and the likely diagnosis: homogeneous pattern suggests anti-dsDNA or anti-histone antibodies (associated with SLE and drug-induced lupus); speckled pattern suggests anti-Smith, anti-RNP, anti-SSA/Ro, or anti-SSB/La antibodies (associated with SLE, mixed connective tissue disease, or Sjogren's syndrome); centromere pattern is highly specific for limited cutaneous systemic sclerosis (CREST syndrome); and nucleolar pattern suggests anti-RNA polymerase or anti-Scl-70 antibodies (associated with systemic sclerosis). A positive ANA alone does not diagnose any disease—it must be interpreted in clinical context.
Por que isso importa
The ANA test is the gateway screening test for systemic autoimmune diseases. A negative ANA at 1:80 or higher effectively rules out SLE (sensitivity >95%). However, a positive ANA is found in many conditions beyond autoimmune disease—up to 15–20% of healthy individuals have a low-titer positive ANA, and prevalence increases with age, particularly in women. The clinical value of an ANA test depends entirely on the pre-test probability: ordering it in a patient with joint pain, rash, serositis, and cytopenias is highly informative, while ordering it as a nonspecific "screening" test in patients with vague fatigue often leads to unnecessary anxiety and further testing.
Faixas de referência normais
| Grupo | Faixa | Unidade |
|---|---|---|
| Negative | <1:40 | titer |
| Low positive (often clinically insignificant) | 1:40–1:80 | titer |
| Moderate positive | 1:160–1:320 | titer |
| High positive (more likely clinically significant) | ≥1:640 | titer |
As faixas de referência podem variar entre laboratórios. Sempre compare seus resultados com as faixas fornecidas pelo seu local de exame.
O que significam níveis altos de ANA
Causas comuns
- Systemic lupus erythematosus (SLE)—positive in >95% of cases
- Drug-induced lupus (hydralazine, procainamide, isoniazid)
- Sjogren's syndrome
- Systemic sclerosis (scleroderma)
- Mixed connective tissue disease
- Polymyositis/dermatomyositis
- Autoimmune hepatitis
- Rheumatoid arthritis (in some patients)
- Healthy individuals (up to 15–20%, usually low titer)
- Older age (higher prevalence of low-titer positive ANA)
- Infections (EBV, hepatitis C) and certain medications
Possíveis sintomas
- A positive ANA itself does not cause symptoms
- Symptoms depend on the underlying condition—may include joint pain, skin rashes, fatigue, mouth ulcers, hair loss, Raynaud's phenomenon, dry eyes/mouth, or muscle weakness
O que fazer: A positive ANA should prompt evaluation of the clinical picture. If autoimmune disease is suspected, order specific antibodies based on the ANA pattern: anti-dsDNA and anti-Smith for SLE, anti-SSA/SSB for Sjogren's, anti-centromere and anti-Scl-70 for systemic sclerosis, anti-Jo-1 for myositis. Check complement levels (C3, C4), CBC, urinalysis, and inflammatory markers. A low-titer ANA (≤1:80) in the absence of suggestive symptoms generally does not warrant further testing. Refer to rheumatology when clinical features align with a systemic autoimmune disease.
O que significam níveis baixos de ANA
Causas comuns
- A negative ANA is the normal result
- ANA-negative lupus occurs rarely (<5% of SLE cases)—these patients may have anti-Ro/SSA antibodies detectable by other methods
Possíveis sintomas
- No symptoms from a negative ANA
O que fazer: A negative ANA is reassuring and effectively rules out SLE in most cases. If clinical suspicion for SLE or Sjogren's remains high despite a negative ANA, consider testing for anti-Ro/SSA antibodies specifically, as these can be present in ANA-negative lupus. No follow-up testing is needed for a negative ANA in the absence of clinical concern.
Quando o exame de ANA é recomendado?
- When systemic lupus erythematosus is clinically suspected (malar rash, photosensitivity, joint pain, serositis, cytopenias)
- When Sjogren's syndrome is suspected (dry eyes, dry mouth, parotid swelling)
- When systemic sclerosis is suspected (Raynaud's, skin thickening, digital ulcers)
- As part of the workup for unexplained inflammatory arthritis
- When autoimmune hepatitis is suspected
Perguntas frequentes
Biomarcadores relacionados
Leitura relacionada
Sintomas
Referências e abordagem de revisão
As páginas do glossário de biomarcadores são explicações educativas e devem ser interpretadas junto com as faixas de referência e observações fornecidas pelo seu laboratório e pelo seu médico. Para conhecer nossos padrões editoriais e processo de revisão, veja nossa Política editorial e a nossa revisão de conteúdo.
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Enviar resultados de exames →Aviso médico: Estas informações são apenas educativas e não substituem orientação, diagnóstico ou tratamento médico profissional. As faixas de referência podem variar entre laboratórios. Sempre converse com seu profissional de saúde sobre a interpretação dos seus resultados específicos.