Interpretation

Presence of anti-cellular antibody (also known as antinuclear antibody) is a characteristic feature of systemic autoimmune rheumatic diseases such as systemic lupus erythematosus, mixed connective tissue disease, Sjogren syndrome and systemic sclerosis (SSc), and inflammatory myopathies (dermatomyositis, anti-synthetase syndrome and necrotizing autoimmune myopathy). It may also be of diagnostic relevance in patients with autoimmune liver diseases.

Patients' sera are screened at 1:80. The following nuclear patterns and their titers are reported: centromere, homogeneous, nuclear dots, nucleolar, speckled, fine dense speckled (also referred to as DFS70), and proliferating cell nuclear antigen (PCNA). If observed, the following cytoplasmic patterns are reported: reticular/AMA (antimitochondrial antibody), cytoplasmic speckled, fibrillar, polar/Golgi-like, or rods and rings. The spindle fiber and centrosome mitotic patterns are also reported if observed. Reported patterns may help guide differential diagnosis, although they may not be specific for individual antibodies or diseases. Negative results do not necessarily rule out systemic autoimmune rheumatic disease.

The antinuclear antibody test lacks diagnostic specificity and is associated with some cancers, infectious, and inflammatory conditions, with variable prevalence in healthy individuals. The lack of diagnostic specificity requires confirmation of positive results using associated antibody tests such as those targeting extractable nuclear antigens.

A positive test result for Scl-70 antibodies may be consistent with a diagnosis of systemic sclerosis in the appropriate clinical context.

A positive result for RNA polymerase III antibody may support a diagnosis of SSc in the appropriate clinical context. Anti-RNA polymerase III autoantibody in patients with SSc is associated with the diffuse cutaneous form of disease and an increased risk of sclerodermal renal crisis.

A negative result indicates no detectable IgG antibodies to RNA polymerase III and does not rule out a diagnosis of SSc. The RNA polymerase III IgG enzyme-linked immunosorbent assay tests only for the RP155 dominant epitope, other epitopes in the antigenic complex are absent and cannot be detected.(6) The overall pooled prevalence of anti-RNA polymerase III antibody is reported to be 11%, 95% CI: 8 to 14, range of 0% to 41% in published studies.(4)