Anti-cytoskeletal pattern (AC-15, 16, and 17)
Autoantibodies to the cytoskeletal microfilaments such as actin, intermediate filaments (such as vimentin) and microtubules (such as tubulin) can be seen in a variety of autoimmune diseases. Whenever an ANA is read, the first step is to see if there is a clearly discernible pattern in the nucleus of the interphase cells. If not, and there is considerable staining in the cytoplasm, then a discernible cytoplasmic pattern should be reported. Identification of fibrous strands in the cytoplasm are reported as "Suspect cytoskeletal, suggest follow-up." Typically anti-cytoskeletal antibodies are reported as "ANA negative, suspect cytoskeletal antibodies present." (The term "suspect" is used because the ANA substrate is not considered "confirmatory" for the identification of cytoskeletal antibodies. Additional follow-up testing is required.) Follow-up testing would include testing for anti-smooth muscle antibodies. Anti-smooth muscle antibodies are seen in autoimmune liver disease. An example of fluorescent staining of this pattern is on the right.
Anti-mitochondrial pattern (AC-21)
The anti-mitochondrial pattern has considerable staining in the cytoplasm, described as discrete speckling "strand of beads." This pattern is reported as "ANA negative, suspect mitochondrial antibodies present." Follow-up testing would include testing for anti-mitochondrial antibodies. Anti-mitochondrial antibodies are seen in patients with primary biliary cirrhosis.
Anti-ribosomal P pattern
About 50% of the time when a sample contains anti-ribosomal antibodies, a positive nucleolar ANA is present along with fine granular staining in the cytoplasm. The other 50% of the time the nucleolar ANA is NOT
present, and only the fine granular cytoplasmic staining is seen. Therefore, depending on the status of the staining in the nucleus of the interphase cells, anti-ribosomal P antibodies can be either ANA positive or negative. The pattern typically presents as "cloudy" fine speckling in the cytoplasm. This pattern would be reported as "ANA positive or negative with strong cytoplasmic speckling, suspect anti-ribosomal P antibodies present." Follow-up testing would include testing for anti-ribosomal P antibodies. Anti-ribosomal P antibodies are very specific for patients with SLE.