Test Catalog

Test ID: ANA2    
Antinuclear Antibodies (ANA), Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluating patients suspected of having a systemic rheumatic disease

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Connective Tissue Disease Cascade (CTDC) in Special Instructions.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Measurement of antinuclear antibodies (ANA) in serum is the most commonly performed screening test for patients suspected of having a systemic rheumatic disease, also referred to as connective tissue disease.(1) ANA occur in patients with a variety of autoimmune diseases, both systemic and organ-specific. They are particularly common in the systemic rheumatic diseases, which include lupus erythematosus (LE), discoid LE, drug-induced LE, mixed connective tissue disease, Sjogren syndrome, scleroderma (systemic sclerosis), CREST (calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia) syndrome, polymyositis/dermatomyositis, and rheumatoid arthritis.(1)


The diagnosis of a systemic rheumatic disease is based primarily on the presence of compatible clinical signs and symptoms. The results of tests for autoantibodies including ANA and specific autoantibodies are ancillary. Additional diagnostic criteria include consistent histopathology or specific radiographic findings. Although individual systemic rheumatic diseases are relatively uncommon, a great many patients present with clinical findings that are compatible with a systemic rheumatic disease and large numbers of tests for ANA are ordered to eliminate the possibility of a systemic rheumatic disease.


See Connective Tissue Disease Cascade (CTDC) in Special Instructions.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

< or =1.0 U (negative)

1.1-2.9 U (weakly positive)

3.0-5.9 U (positive)

> or =6.0 U (strongly positive)

Reference values apply to all ages.

Interpretation Provides information to assist in interpretation of the test results

A large number of healthy individuals have weakly-positive antinuclear antibody (ANA) results, many of which are likely to be clinical false-positives; therefore, second-order testing of all positive ANA yields a very low percentage of positive results to the specific nuclear antigens.


A positive ANA result at any level is consistent with the diagnosis of systemic rheumatic disease, but a result greater than or equal to 3.0 U is more strongly associated with systemic rheumatic disease than a weakly-positive result.


Positive ANA results greater than 3.0 U are associated with the presence of detectable autoantibodies to specific nuclear antigens. The nuclear antigens are associated with specific diseases (eg, anti-Scl 70 is associated with scleroderma) and can be detected with second-order testing.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Some patients without clinical evidence of an autoimmune disease or a systemic rheumatic disease may have a detectable level of antinuclear antibody (ANA). This finding is more common in women than men, and the frequency of a detectable ANA in healthy women over 40 years old may approach 15% to 20%. ANA may also be detectable following viral illnesses, in chronic infections, or in patients treated with many different medications.

Supportive Data

In a study performed in the Mayo Clinic immunology antibody laboratory, more than 75% of patients with a systemic rheumatic disease had antinuclear antibody (ANA) results greater than 3.0 U and the positive predictive value of these results for a systemic rheumatic disease was greater than 85%. Weakly positive ANA results were not a strong indicator of systemic rheumatic disease. The likelihood of finding an autoantibody to a specific nuclear antigen on a second-order testing increased directly with the level of ANA: 92% of sera that had detectable autoantibodies on second-order testing had an ANA level greater than 3.0 U.(2)


An ANA result of greater than or =3.0 U is the cutoff for CTDC / Connective Tissue Disease Cascade, Serum, a test algorithm designed to evaluate patients with signs and symptoms consistent with connective tissue diseases and the preferred initial test for these patients.


Results of tests for ANA performed by ELISA in the immunology antibody laboratory show that ELISA and traditional indirect immunofluorescence methods for ANA are substantially equivalent.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Kavanaugh A, Tomar R, Reveille J, et al: Guidelines for use of the antinuclear antibody test and tests for specific autoantibodies to nuclear antigens. Pathol Lab Med 2000;124:71-81

2. Homburger HA, Cahen YD, Griffiths J, Jacob GL: Detection of antinuclear antibodies: comparative evaluation of enzyme immunoassay and indirect immunofluorescence methods. Arch Pathol Lab Med 1998;122:993-999

Special Instructions Library of PDFs including pertinent information and forms related to the test