Q: What do antinuclear antibodies mean?
A: Antibodies are proteins created by lymphocytes to maintain immune system function. There are two types of lymphocytes, T-lymphocytes (T-cells) and B-lymphocytes (B-cells), that help protect the immune system from viruses, bacteria, and malignancy.1 Antibodies enable the immune system to defend itself from infection. B-lymphocytes recognize an antigen that previously entered the body and produce antibodies to these pathogenetic antigens.1 In some people, these antibodies incorrectly identify normal proteins (self-proteins) as foreign and harmful to the person.2,3 Self-proteins are called autoantibodies, but when they attack the nucleus of a cell, they are also called antinuclear antibodies (ANAs).
ANAs may cause systemic inflammation and tissue damage.2-5 Most people have autoantibodies, including ANAs in small amounts.2 Still, ANAs in large amounts may indicate that the person's body is attacking itself, leading to autoimmune diseases including but not limited to systemic lupus erythematosus, rheumatoid arthritis, Sjogren syndrome, scleroderma, systemic sclerosis, dermatomyositis, polymyositis, autoimmune hepatitis, inflammatory bowel disease, mixed connective tissue disease, and Hashimoto thyroiditis.2-5 Some medications such as procainamide, hydralazine, and isoniazid, infections, and cancer may also lead to detectable ANAs.2,3
ANA detection
The most sensitive method of detecting ANAs and all other autoantibodies in the cell nucleus is indirect immunofluorescence (IIF) reported as a titer.6 For example, 1:80, 1:160, and 1:320.6 A second method of detecting ANAs is enzyme-linked immunosorbent assay (ELISA).6 The ELISA method detects ANAs from a broad perspective like IIF.6 A negative result is reported as negative by ELISA.6 A positive result is quantified by titer.6 Another type of ELISA detects ANA-specific antigens that correlate with specific autoimmune diseases (see ANA types and clinical associations).2-6 It's common practice to combine broad ANA detection with specific antigenic ANA testing.6 A positive ANA in isolation should never be used to establish a diagnosis, and a negative ANA should never be used to exclude a diagnosis.3 The ANA isn't specific for autoimmune disease but is used as a tool with other lab studies and the patient's signs and symptoms to establish a specific diagnosis.3
ANA associations
ANAs are observed under the microscope for staining patterns that indicate specific autoimmune disease processes.2-6 (1) Homogenous pattern: systemic lupus erythematosus; drug-induced lupus. (2) Rim pattern: systemic lupus erythematosus; autoimmune hepatitis. (3) Speckled pattern: Systemic lupus erythematosus; mixed connective tissue disease; Sjogren syndrome; systemic sclerosis. (4) Nucleolar pattern: systemic sclerosis. (5) Centromere pattern: scleroderma. The overarching broad ANA testing and staining pattern should be identified with the specific antigen(s) that correlate with the patient's signs and symptoms.2-6
Nursing assessment
ANAs are lab markers of inflammation in autoimmune diseases.3,7 The nurse should correlate ANAs with other markers of inflammation such as c-reactive protein and erythrocyte sedimentation rate.3,7 The nurse should perform a health history interview to determine comorbidities and medication history.3,7 Inflammation can manifest in many ways. For example, fatigue, fever, anorexia, the onset of lesions and rashes, joint point, muscle soreness and stiffness, and chest pain related to lung or heart involvement.3,7 Lung and heart sounds should be auscultated.7 Respiratory rate, depth, effort, and cardiac rate and rhythm should be assessed.7 Another indication of inflammation is serum complement levels.8 Complement proteins are released by the liver in acute inflammation and infection to engulf and rid the body of antigens.8 An abnormally low complement level, particularly complement-3 (C3) and complement-4 (C4) indicates that these proteins are consumed by the antigen(s) and are a marker of disease severity.8 Chronic inflammation also interferes with erythropoietin production by the kidneys.7 Erythropoietin is a hormone that stimulates red blood cell (RBC) production. Anemia may result. Nurses should instruct the patient to conserve energy, get plenty of rest, and report the onset of new symptoms.7
The first step in diagnosis
A positive ANA is a valuable tool in establishing an autoimmune disease diagnosis. The level of ANA doesn't always equate with disease severity. For example, a high level doesn't necessarily mean that a patient has a worse disease than a patient with a low level of ANA and vice versa. The patient's signs and symptoms and results from diagnostic lab and imaging studies need to be assessed, trended, and analyzed to establish a care plan.
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