Enzyme inhibitory antibody to pyruvate dehydrogenase: diagnostic utility in primary biliary cirrhosis

In primary biliary cirrhosis, autoantibodies are produced to the family of 2-oxoacid dehydrogenase complexes. These 'anti-mitochondrial' antibodies are traditionally detected by immunofluorescence but this method of detection is subjective and labour-intensive. We assessed an enzymatic mitochondrial antibody (EMA) assay based on antibody inhibition of enzymatic activity of pyruvate dehydrogenase complex in wells of microtitre plates with a colorimetric read-out. We tested 48 Australian and 1947 Japanese patients with primary biliary cirrhosis, 306 normal subjects and 691 patients with various hepatic and non-hepatic diseases. The overall sensitivity of the EMA for the diagnosis of primary biliary cirrhosis, 82%, was slightly lower than that of immunofluorescence, 90%. The advantages of the EMA test include high specificity, >99%, and semi-automated features facilitating objectivity, rapidity, simplicity and economy. The EMA test could be particularly applicable to population screening for early primary biliary cirrhosis.