title: Differentiation of autoimmune pancreatitis from pancreas cancer: utility of anti-amylase and anti-carbonic anhydrase II autoantibodies.
abstract: OBJECTIVE
  To investigate the utility of different combinations of serum anti-carbonic anhydrase II antibodies (CA II Abs), anti-α amylase antibodies (AMY-α Abs) and IgG4 levels for the diagnosis of autoimmune pancreatitis (AIP).
  
  
  METHODS
  We recruited 93 patients with clinical suspicion for AIP and 94 patients as control groups between June 2003 and October 2009. Serum antibodies were measured using homemade enzyme linked immunosorbent assay and IgG4 levels were determined by nephelometry.
  
  
  RESULTS
  Both CA-II Abs and AMY-α Abs had the highest sensitivity (83%) although AMY-α Abs (89%) were more specific than CA-II Abs (75%). The presence of increased IgG4 levels was the most specific serological marker (94%), but it had the lowest sensitivity (58%). The combination of the three serological markers altogether had the highest specificity (99%) and positive predictive value (PPV) (86%), but they had a rather low sensitivity (50%). When we combined CA-II Abs and AMY-α Abs without IgG4 levels, we got the highest sensitivity (75%) and negative predictive value (98%) but the specificity and the PPV decreased to 93 and 50%, respectively. Importantly, AMY-α Abs were not detected in pancreas cancer.
  
  
  CONCLUSIONS
  The presence of serum CA-II and AMY-α Abs with increased IgG4 is useful in the differential diagnosis of AIP from pancreatic cancer.
authors.affiliation: Servicio Inmunología, Hospital Universitario Marqués de Valdecilla-IFIMAV, Avda. Valdecilla s/n, 39008 Santander, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Sánchez-Castañón
authors.affiliation: Gastroenterology Service, Hospital Universitario Marqués de Valdecilla-IFIMAV, Santander, Spain.
authors.forename: G
authors.initials: G
authors.lastname: de Las Heras-Castaño
authors.affiliation: Servicio Inmunología, Hospital Universitario Marqués de Valdecilla-IFIMAV, Avda. Valdecilla s/n, 39008 Santander, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Gómez
authors.affiliation: Servicio Inmunología, Hospital Universitario Marqués de Valdecilla-IFIMAV, Avda. Valdecilla s/n, 39008 Santander, Spain.
authors.forename: M
authors.initials: M
authors.lastname: López-Hoyos
keywords: Anti-carbonic anhydrase II antibodies; Anti-α amylase antibodies; Autoimmune pancreatitis; Diagnosis; IgG4; Pancreatic cancer