Diagnostic Use
Autoimmune diseases are classified as either “tissue or organ specific” or as “non organ specific”. The first group are diseases such as thyroiditis, myasthenia gravis, diabetes mellitus, Addison disease. Some non-organ specific diseases are systemic lupus erythematosus, rheumatoid arthritis and progressive systemic sclerosis. The latter group is an autoimmune response to antigens common to various organs and tissues in the body whereas the former is an autoimmune response to antigens present in only one particular tissue or organ.
Mitochondrial Antibodies
Seen in 95% of patients with primary biliary cirrhosis (PBC) with 50% of the titres being greater than 1:160. Seen in low titres in patients with thyrotoxicosis, Hashimoto’s thyroiditis and pernicious anaemia. 2 – 10% of patients with rheumatoid arthritis, SLE, Sjogren syndrome and systemic sclerosis show positive results. Low titre mitochondrial antibodies found also in patients with biological false positive tests for syphilis i.e. VDRL positive, TPHA and FTA negative.
Mitochondrial antibodies are seen, in various degrees, in chronic active hepatitis and cryptogenic cirrhosis. Less than 3% of patients with Addison’s disease, myasthenia gravis and autoimmune haemolytic anaemia have positive mitochondrial antibodies.
Reference Intervals
Negative/Normal: L20
Positive Titre: 20 – G1280
To maximise assay sensitivity, AMA antibody negative results are reported as <20 or L20
A positive result in titre range 1:40 – 1:80 is regarded as being of borderline significance.
Note: A repeat specimen should be tested in 2 weeks to check if there is an increase in titre.
A positive result in titre range 1:160 or greater is of significance.
High AMA is commonly seen in PBC.
Test Method
Indirect Immunofluorescence Assay (IFA) - automated
HTZ robotic processing
Manual LED microscopy visual evaluation
Limitations / Interference
Grossly haemolysed and/or high lipaemic serum specimens.
Uncertainty of Measurement
Accepted variation for reported titres is +/- a single doubling dilution.