Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
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        AMA test, blood
      
Anti-mitochondrial antibody (AMA) is an autoantibody which has been said to be found in some liver diseases...generally accepted as a marker of primary biliary cirrhosis (PBC). We use a test system with cryostat sections of rat kidney and stomach, and or rat liver as the substrate at a beginning dilution of patient's serum of 1:20. The use of animal tissue avoids interference from HLA and/or blood group Abs that may occur were human substrate used. Incidental Abs may show up in this IFA system such as ASMA, APCA, ANA, ARA, ABBA, anti-canalicular Ab, anti-liver cell membrane Ab, and anti-ribosomal Ab. [see table] Mitochondria stain in parietal cell, hepatocytic, and renal tubular cell cytoplasms. CAUTION: There are false positives such that: reactivity at dilution of serum <1:40 represents "probable nonspecific reactivity"; @ 1:40 is a "nonspecific positive reactivity"; 1:80 is "significant serologic positivity, PBC?" We have documented instances of levels >1:160 that were not PBC (L13-202)...so, liver biopsy findings are crucial to proper total case interpretation. This antibody can be detected in other media, such as DIF/DFA skin biopsy preps [S-03-8966].

Associations with undetectable Ab:

  • normalcy.
  • watch out for cases of AMA negative and ANA positive...may be autoimmune cholangitis if liver biopsy shows chronic portal triaditis and ductopenia or duct injury & one of the other auto-duct-related antibodies positive3. Serology chart HERE.
  • viral hepatitis1.
  • hepatitis of other types with collateral biliary injury but AMA negative & also no other auto-duct-related antibodies positive.

Associations with elevated levels:

  • PBC in 75-95% of cases1;  at 1:160-1:6000 (other diseases at lower levels) and do not correlate with either severity of disease or response to immunosuppressive therapy.2; once the test is reactive at 1:160 or higher, it indicates "significant serologic evidence suspicious for primary biliary hepatitis/cirrhosis" [LMC-01-2794, LMC-01-1280; LMC-02-3489; LMC-02-4906]
  • autoimmune (chronic active2) hepatitis  0-30% of cases1
  • AMA positive PLUS PBC histology BUT with clearly elevated LFTs and other evidence of chronic active  hepatitis might be a PBC-AIH overlap syndrome
  • primary sclerosing cholangitis (PSC) is AMA positive in <5% of cases
  • extra-hepatic biliary obstruction 0-5% of cases1
  • non-obstructive biliary tract disease2
  • hepatic malignancy2
  • collagen vascular diseases2
  • cryptogenic cirrhosis 0-25% of cases1
  • drug induced hepatitis 50-80% of cases1
  • false pos. = to, 1:80 (L13-202) & > 1:160 in : NASH [LMC-02-3489]. 
REFERENCES:

  1. A B C's of Interpretive Laboratory Data, 2nd Ed., Seymour Bakerman, MD, PhD, 1984.
  2. Lex. Med. Lab. procedure manual and its references as of 7/01.
  3. Am. Assoc. for Study of Liver Diseases (AASLD) 2010 "AASLD Practice Guidelines: Diagnosis and Management of AIH"...all about serology tests HERE.
 
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