title: Clinical evaluation of serum antimitochondrial antibody-negative primary biliary cirrhosis.
abstract: BACKGROUND
  Primary biliary cirrhosis (PBC) is characterized by frequent presence of antimitochondrial antibodies (AMAs). The sensitivity and specificity of AMA for PBC are both greater than 90%-95%, so the presence of AMA in serum is the major hallmark in PBC. However, it has long been recognized that in 5%-10% of patients the clinical, biochemical and histological features are diagnostic for PBC, but their sera are consistently tested negative for AMA/AMA-M2. This study aimed to evaluate whether the presence of AMA alters the clinical, serological and histological features of the disease.
  
  
  METHODS
  Clinical data of 70 patients clinically and/or histologically diagnosed with PBC were reviewed. AMA-negative and AMA-positive patients were compared in terms of clinical, biochemical, immunological and histological features.
  
  
  RESULTS
  At presentation, 11 patients were serum AMA/AMA-M2 negative. At the initial visit, AMA-negative and AMA-positive patients were similar in terms of age, sex, clinical manifestations, liver biochemistries and histological findings. The mean level of serum immunoglobulin M (IgM) was significantly lower in AMA-negative PBC patients than in AMA-positive PBC patients (2851+/-1418 mg/L vs 6361+/-4928 mg/L, P=0.033). Serum antinuclear antibodies (ANA) and/or smooth muscle antibodies (SMA) were more frequently positive in the AMA-negative PBC patients than in the AMA-positive patients (81.8% vs 40.7%, P=0.031).
  
  
  CONCLUSIONS
  AMA-negative PBC patients are characterized by relatively lower levels of serum IgM and a higher prevalence of serum ANA/SMA and are not associated with substantial differences in the clinical  biochemical and histological spectrum of the disease.
authors.affiliation: Liver Research Center, Beijing Friendship Hospital, Capital University of Medical Sciences, Beijing 100050, China. frankliver@yahoo.com.cn
authors.forename: Fu-Kui
authors.initials: FK
authors.lastname: Zhang
authors.forename: Ji-Dong
authors.initials: JD
authors.lastname: Jia
authors.forename: Bao-En
authors.initials: BE
authors.lastname: Wang
mesh_terms: D001323:Autoantibodies / Q000276:immunology*; D001327:Autoimmune Diseases / Q000276:immunology* / Q000473:pathology; D005260:Female; D006801:Humans; D008105:Liver Cirrhosis, Biliary / Q000276:immunology* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000276:immunology*
chemical_list: D001323:Autoantibodies