title: Value of serum IgG4 in the diagnosis of IgG4-related disease and in differentiation from rheumatic diseases and other diseases.
abstract: IgG4-related disease (IgG4-RD) is a novel disease entity that includes Mikulicz's disease, autoimmune pancreatitis (AIP), and many other conditions. It is characterized by elevated serum IgG4 levels and abundant IgG4-bearing plasmacyte infiltration of involved organs. We postulated that high levels of serum IgG4 would comprise a useful diagnostic tool, but little information is available about IgG4 in conditions other than IgG4-RD, including rheumatic diseases. Several reports have described cutoff values for serum IgG4 when diagnosing IgG4-RD, but these studies mostly used 135 mg/dL in AIP to differentiate from pancreatic cancer instead of rheumatic and other common diseases. There is no evidence for a cutoff serum IgG4 level of 135 mg/dL for rheumatic diseases and common diseases that are often complicated with rheumatic diseases. The aim of this work was to re-evaluate the usual cutoff serum IgG4 value in AIP (135 mg/dL) that is used to diagnose whole IgG4-RD in the setting of a rheumatic clinic by measuring serum IgG4 levels in IgG4-RD and various disorders. We therefore constructed ROC curves of serum IgG4 levels in 418 patients who attended Sapporo Medical University Hospital due to IgG4-RD and various rheumatic and common disorders. The optimal cut-off value of serum IgG4 for a diagnosis of IgG4-RD was 144 mg/dL, and the sensitivity and specificity were 95.10 and 90.76%, respectively. Levels of serum IgG4 were elevated in IgG4-RD, Churg-Strauss syndrome, multicentric Castleman's disease, eosinophilic disorders, and in some patients with rheumatoid arthritis, systemic sclerosis, chronic hepatitis, and liver cirrhosis. The usual cut-off value of 135 mg/dL in AIP is useful for diagnosing whole IgG4-RD, but high levels of serum IgG4 are sometimes observed in not only IgG4-RD but also other rheumatic and common diseases.
authors.affiliation: First Department of Internal Medicine, Sapporo Medical University School of Medicine, South 1-West 16, Chuo-ku, Sapporo, Hokkaido 0608543, Japan. mocha@cocoa.plala.or.jp
authors.forename: Motohisa
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tabeya
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Naishiro
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Yajima
authors.forename: Keisuke
authors.initials: K
authors.lastname: Ishigami
authors.forename: Yui
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Mikiko
authors.initials: M
authors.lastname: Obara
authors.forename: Chisako
authors.initials: C
authors.lastname: Suzuki
authors.forename: Kentaro
authors.initials: K
authors.lastname: Yamashita
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hayashi
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sasaki
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sugaya
authors.forename: Tadao
authors.initials: T
authors.lastname: Ishida
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Takano
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Himi
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Norihiro
authors.initials: N
authors.lastname: Nishimoto
authors.forename: Saho
authors.initials: S
authors.lastname: Honda
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Kohzoh
authors.initials: K
authors.lastname: Imai
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Shinomura
mesh_terms: D000328:Adult; D001327:Autoimmune Diseases / Q000097:blood / Q000175:diagnosis*; D015267:Churg-Strauss Syndrome / Q000097:blood / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D008882:Mikulicz' Disease / Q000097:blood / Q000175:diagnosis*; D010195:Pancreatitis / Q000097:blood / Q000175:diagnosis*; D012216:Rheumatic Diseases / Q000097:blood / Q000175:diagnosis*
chemical_list: D007074:Immunoglobulin G