title: Elevated tumour marker CA19-9: clinical interpretation and influence of obstructive jaundice.
abstract: OBJECTIVE
  The tumour marker CA19-9 has been promoted as a reliable test for the detection of pancreatobiliary malignancy, yet its diagnostic role remains poorly defined. In this study the clinical interpretation of a raised serum CA19-9 level has been evaluated, with particular reference to obstructive jaundice.
  
  
  METHODS
  One hundred and sixty-four patients with a CA19-9 level above 33 U/ml were studied. Serum CA19-9 was compared with clinical diagnosis and correlated with serum bilirubin level. In a subgroup of jaundiced patients (16 benign and 15 malignant cases), follow-up CA19-9 levels were determined 2 weeks after biliary drainage.
  
  
  RESULTS
  The median CA19-9 level was lower in benign cases (102 (IQR 50-264) U/ml) than those with pancreatobiliary tumours (910 (IQR 263-6170) U/ml; P<0.01), although the overlap was substantial. In benign jaundiced cases, a positive correlation was observed between bilirubin and CA19-9 elevation (R=0.41, P<0.01). Relief of jaundice was associated with a fall in CA19-9 level in all benign cases and in nine of the 15 with malignancy.
  
  
  CONCLUSIONS
  Confident discrimination between benign and malignant disease could not be made on the basis of a solitary elevated CA19-9 measurement. Hyperbilirubinaemia was associated with a further deterioration in specificity and caution is warranted when interpreting the results in jaundiced patients. Overall, only one half of patients with an elevated CA19-9 level ultimately proved to harbour a malignancy.
authors.affiliation: Department of Surgery, St Mary's Hospital, London, UK.
authors.forename: D V
authors.initials: DV
authors.lastname: Mann
authors.forename: R
authors.initials: R
authors.lastname: Edwards
authors.forename: S
authors.initials: S
authors.lastname: Ho
authors.forename: W Y
authors.initials: WY
authors.lastname: Lau
authors.forename: G
authors.initials: G
authors.lastname: Glazer
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001661:Biliary Tract Neoplasms / Q000097:blood / Q000150:complications / Q000175:diagnosis* / Q000276:immunology; D001663:Bilirubin / Q000097:blood; D014408:Biomarkers, Tumor / Q000097:blood*; D018395:CA-19-9 Antigen / Q000097:blood*; D002779:Cholestasis / Q000097:blood / Q000209:etiology* / Q000276:immunology; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000097:blood / Q000150:complications / Q000175:diagnosis* / Q000276:immunology; D011237:Predictive Value of Tests
chemical_list: D014408:Biomarkers, Tumor; D018395:CA-19-9 Antigen; D001663:Bilirubin