title: Poor positive predictive value of serum immunoglobulin G4 concentrations in the diagnosis of immunoglobulin G4-related sclerosing disease.
abstract: BACKGROUND
  Immunoglobulin G4 (IgG4)-related sclerosing disease is a recently described clinicopathological entity with diverse manifestations including, amongst others, autoimmune pancreatitis, sclerosing cholangitis, sclerosing sialadenitis and retroperitoneal fibrosis. Elevated serum IgG4 concentration has been described as the hallmark of this condition with reported good sensitivity and specificity.
  
  
  OBJECTIVE
  We sought to establish the utility of serum IgG4 concentrations in the diagnosis of IgG4-related sclerosing disease by determining how many serum samples with elevated IgG4 from an unselected population would originate from patients who fulfilled criteria for this diagnosis.
  
  
  METHODS
  The clinical features and laboratory characteristics of patients whose serum IgG4 concentration was greater than 1.30 g/L were analysed retrospectively from a total of 1,258 IgG subclass measurements performed in a tertiary hospital diagnostic laboratory.
  
  
  RESULTS
  Eighty patients (6.4%) had elevated IgG4 concentrations greater than 1.30 g/L. Nine of 61 patients had the diagnosis of IgG4-related sclerosing disease, giving a poor positive predictive value of 15%. The median serum IgG4 concentrations of those with and without IgG4-related sclerosing disease were 2.16 g/L and 1.86 g/L, respectively (p = 0.22).
  
  
  CONCLUSIONS
  Serum IgG4 concentration has poor positive predictive value in the diagnosis of IgG4-related sclerosing disease and, therefore, the clinical significance of elevated serum IgG4 concentration alone must be interpreted with caution.
authors.affiliation: Department of Clinical Immunology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Yun
authors.affiliation: Department of Clinical Immunology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.
authors.forename: Louise
authors.initials: L
authors.lastname: Wienholt
authors.affiliation: Department of Clinical Immunology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Adelstein
keywords: Autoimmune diseases; Immunoglobulin G; Mikulicz' disease; Pancreatitis
references.citation: Ann Rheum Dis. 2015 Jan;74(1):14-8
references.pmid: 24651618
references.citation: BMC Med. 2006 Oct 06;4:23
references.pmid: 17026742
references.citation: Clin Chim Acta. 2009 Oct;408(1-2):25-8
references.pmid: 19580797
references.citation: Am J Gastroenterol. 2007 Aug;102(8):1646-53
references.pmid: 17555461
references.citation: Gut. 2007 Oct;56(10):1471-2
references.pmid: 17504944
references.citation: Clin Chem. 2003 Nov;49(11):1924-9
references.pmid: 14578325
references.citation: Intern Med. 2008;47(4):291-4
references.pmid: 18277032
references.citation: J Gastroenterol Hepatol. 2009 Jan;24(1):15-36
references.pmid: 19067780
references.citation: J Immunol. 1983 Feb;130(2):722-6
references.pmid: 6600252
references.citation: N Engl J Med. 2001 Mar 8;344(10):732-8
references.pmid: 11236777
references.citation: Scand J Rheumatol. 2004;33(6):432-3
references.pmid: 15794205
references.citation: Curr Opin Rheumatol. 2011 Jan;23(1):18-23
references.pmid: 21124083
references.citation: Clin Allergy. 1976 May;6(3):237-40
references.pmid: 939036
references.citation: Eur J Gastroenterol Hepatol. 2011 Feb;23(2):139-45
references.pmid: 21287719
references.citation: Am J Surg Pathol. 2005 Feb;29(2):275-8
references.pmid: 15644785
references.citation: Clin Exp Nephrol. 2007 Jun;11(2):168-173
references.pmid: 17593518
references.citation: Int Arch Allergy Immunol. 2010;152 Suppl 1:47-53
references.pmid: 20523063
references.citation: Pancreas. 2014 Jul;43(5):704-7
references.pmid: 24632552
references.citation: Am J Gastroenterol. 2006 Sep;101(9):2070-5
references.pmid: 16879434
references.citation: Am J Surg Pathol. 2009 Dec;33(12):1833-9
references.pmid: 19950407
references.citation: Rheumatol Int. 2010 Apr;30(6):837-40
references.pmid: 20052478
references.citation: Pancreatology. 2006;6(1-2):132-7
references.pmid: 16327291