title: Serum level of Ca 19-9 increases ability of IgG4 test to distinguish patients with autoimmune pancreatitis from those with pancreatic carcinoma.
abstract: BACKGROUND
  Autoimmune pancreatitis (AIP) is often difficult to distinguish from pancreatic carcinoma or other pancreatobiliary diseases. High serum levels of carbohydrate antigen 19-9 (Ca 19-9) are indicative of malignancies, whereas high levels of immunoglobulin (Ig)G4 (>1.4 g/l) are characteristic of AIP. We investigated whether serum levels of these proteins can differentiate between these diseases.
  
  
  METHODS
  We measured levels of Ca 19-9 and IgG4 in serum samples from 33 patients with AIP, 53 with pancreatic carcinoma, and 145 with other pancreatobiliary disorders. We determined cut-off levels for each assay. Logistic regression analysis was used to evaluate combined data on Ca 19-9, IgG4, and bilirubin levels.
  
  
  RESULTS
  Low levels of Ca 19-9 were independently associated with AIP, compared with pancreatic adenocarcinoma [odds ratio (OR) 0.28; 95% confidence interval (CI) 0.13-0.59; p = 0.0001]. Using an upper level of 74 U/ml, the assay for Ca 19-9 identified patients with AIP with 73% sensitivity and 74% specificity. Using a lower level of 2.6 g/l, the assay for IgG4 identified these patients with 70% sensitivity and 100% specificity. Combining data, levels of Ca 19-9 < 74 U/ml and IgG4 > 1.0 g/l identified patients with AIP with 94% sensitivity and 100 % specificity.
  
  
  CONCLUSIONS
  Patients with AIP have lower levels of Ca 19-9 than those patients with pancreatic carcinoma. Measurement of either the Ca 19-9 or the IgG4 level alone are not accurate enough for diagnosis. However, the combination of Ca 19-9 < 74 U/ml and IgG4 > 1.0 g/l distinguishes patients with AIP from those patients with pancreatic carcinoma with 94% sensitivity and 100% specificity.
authors.affiliation: Department of Gastroenterology and Hepatology, Erasmus University Medical Center, Rotterdam, The Netherlands, mvanheerde@amphia.nl.
authors.forename: Marianne J
authors.initials: MJ
authors.lastname: van Heerde
authors.forename: J
authors.initials: J
authors.lastname: Buijs
authors.forename: B E
authors.initials: BE
authors.lastname: Hansen
authors.forename: M
authors.initials: M
authors.lastname: de Waart
authors.forename: C H J
authors.initials: CH
authors.lastname: van Eijck
authors.forename: G
authors.initials: G
authors.lastname: Kazemier
authors.forename: C J
authors.initials: CJ
authors.lastname: Pek
authors.forename: J W
authors.initials: JW
authors.lastname: Poley
authors.forename: M J
authors.initials: MJ
authors.lastname: Bruno
authors.forename: E J
authors.initials: EJ
authors.lastname: Kuipers
authors.forename: H R
authors.initials: HR
authors.lastname: van Buuren
mesh_terms: D000328:Adult; D000368:Aged; D001327:Autoimmune Diseases / Q000097:blood / Q000175:diagnosis / Q000276:immunology; D001663:Bilirubin / Q000097:blood; D018395:CA-19-9 Antigen / Q000097:blood* / Q000378:metabolism; D002277:Carcinoma / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D010195:Pancreatitis / Q000097:blood* / Q000175:diagnosis* / Q000276:immunology; D012698:Serologic Tests
chemical_list: D018395:CA-19-9 Antigen; D007074:Immunoglobulin G; D001663:Bilirubin