title: Validation of the Japanese disease severity classification and the GAP model in Japanese patients with idiopathic pulmonary fibrosis.
abstract: BACKGROUND
  The clinical course of idiopathic pulmonary fibrosis (IPF) shows great inter-individual differences. It is important to standardize the severity classification to accurately evaluate each patient׳s prognosis. In Japan, an original severity classification (the Japanese disease severity classification, JSC) is used. In the United States, the new multidimensional index and staging system (the GAP model) has been proposed. The objective of this study was to evaluate the model performance for the prediction of mortality risk of the JSC and GAP models using a large cohort of Japanese patients with IPF.
  
  
  METHODS
  This is a retrospective cohort study including 326 patients with IPF in the Hokkaido prefecture from 2003 to 2007. We obtained the survival curves of each stage of the GAP and JSC models to perform a comparison. In the GAP model, the prognostic value for mortality risk of Japanese patients was also evaluated.
  
  
  RESULTS
  In the JSC, patient prognoses were roughly divided into two groups, mild cases (Stages I and II) and severe cases (Stages III and IV). In the GAP model, there was no significant difference in survival between Stages II and III, and the mortality rates in the patients classified into the GAP Stages I and II were underestimated.
  
  
  CONCLUSIONS
  It is difficult to predict accurate prognosis of IPF using the JSC and the GAP models. A re-examination of the variables from the two models is required, as well as an evaluation of the prognostic value to revise the severity classification for Japanese patients with IPF.
authors: Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, South-1 West-16 Chuo-ku, Sapporo, Hokkaido 060-8556, Japan. Electronic address: shun_kondo@sapmed.ac.jp.
authors: Shun
authors: S
authors: Kondoh
authors: Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, South-1 West-16 Chuo-ku, Sapporo, Hokkaido 060-8556, Japan. Electronic address: hchiba@sapmed.ac.jp.
authors: Hirofumi
authors: H
authors: Chiba
authors: Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, South-1 West-16 Chuo-ku, Sapporo, Hokkaido 060-8556, Japan. Electronic address: hnishiki@sapmed.ac.jp.
authors: Hirotaka
authors: H
authors: Nishikiori
authors: Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, South-1 West-16 Chuo-ku, Sapporo, Hokkaido 060-8556, Japan. Electronic address: y.umeda@sapmed.ac.jp.
authors: Yasuaki
authors: Y
authors: Umeda
authors: Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, South-1 West-16 Chuo-ku, Sapporo, Hokkaido 060-8556, Japan. Electronic address: kuronumak@sapmed.ac.jp.
authors: Koji
authors: K
authors: Kuronuma
authors: Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, South-1 West-16 Chuo-ku, Sapporo, Hokkaido 060-8556, Japan. Electronic address: ohtsukam@sapmed.ac.jp.
authors: Mitsuo
authors: M
authors: Otsuka
authors: Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, South-1 West-16 Chuo-ku, Sapporo, Hokkaido 060-8556, Japan. Electronic address: gyamada@sapmed.ac.jp.
authors: Gen
authors: G
authors: Yamada
authors: Department of Public Health, Sapporo Medical University School of Medicine, Japan. Electronic address: hohnishi@sapmed.ac.jp.
authors: Hirofumi
authors: H
authors: Ohnishi
authors: Department of Public Health, Sapporo Medical University School of Medicine, Japan. Electronic address: mitsurum@sapmed.ac.jp.
authors: Mitsuru
authors: M
authors: Mori
authors: Department of Respiratory Medicine and Allergy, Tosei General Hospital, Japan. Electronic address: konyasu2005@yahoo.co.jp.
authors: Yasuhiro
authors: Y
authors: Kondoh
authors: Department of Respiratory Medicine and Allergy, Tosei General Hospital, Japan. Electronic address: taniguchi@tosei.or.jp.
authors: Hiroyuki
authors: H
authors: Taniguchi
authors: Division of Respiratory Medicine, Toho University Omori Medical Center, Japan. Electronic address: sahomma@med.toho-u.ac.jp.
authors: Sakae
authors: S
authors: Homma
authors: Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, South-1 West-16 Chuo-ku, Sapporo, Hokkaido 060-8556, Japan. Electronic address: htaka@sapmed.ac.jp.
authors: Hiroki
authors: H
authors: Takahashi
mesh_terms: D000368:Aged; D002965:Classification; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D008962:Models, Theoretical; D011658:Pulmonary Fibrosis / Q000145:classification* / Q000401:mortality; D015203:Reproducibility of Results; D012189:Retrospective Studies
keywords: GAP model; Idiopathic pulmonary fibrosis; Japanese disease severity classification; Validation