Hirotaka Nishikiori1, Hirofumi Chiba2, Sang Hoon Lee3, Shun Kondoh4, Ken-Ichi Kamo5, Koshi Nakamura6, Kimiyuki Ikeda7, Koji Kuronuma8, Man Pyo Chung9, Yasuhiro Kondoh10, Sakae Homma11, Naohiko Inase12, Moo Suk Park13, Hiroki Takahashi14. 1. Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, Japan. Electronic address: hnishiki@sapmed.ac.jp. 2. Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, Japan. Electronic address: hchiba@sapmed.ac.jp. 3. Division of Pulmonology, Department of Internal Medicine, Severance Hospital, Institute of Chest Diseases, Yonsei University College of Medicine, Republic of Korea. Electronic address: cloud9@yuhs.ac. 4. Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, Japan. Electronic address: shun_kondo@sapmed.ac.jp. 5. Center for Medical Education, Sapporo Medical University School of Medicine, Japan. Electronic address: kamo@sapmed.ac.jp. 6. Department of Public Health and Hygiene, University of the Ryukyus Graduate School of Medicine, Japan. Electronic address: knakamur@med.u-ryukyu.ac.jp. 7. Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, Japan. Electronic address: ikeda@sapmed.ac.jp. 8. Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, Japan. Electronic address: kuronumak@sapmed.ac.jp. 9. Division of Pulmonary and Critical Care Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Republic of Korea. Electronic address: mpchung@skku.edu. 10. Department of Respiratory Medicine and Allergy, Tosei General Hospital, Japan. Electronic address: kondoh@tosei.or.jp. 11. Department of Advanced and Integrated Interstitial Lung Diseases Research, School of Medicine, Toho University, Japan. Electronic address: sahomma@med.toho-u.ac.jp. 12. Department of Respiratory Medicine, Tokyo Medical and Dental University, Japan. Electronic address: inase-n@kkr.hiratsuka.kanagawa.jp. 13. Division of Pulmonology, Department of Internal Medicine, Severance Hospital, Institute of Chest Diseases, Yonsei University College of Medicine, Republic of Korea. Electronic address: PMS70@yuhs.ac. 14. Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, Japan. Electronic address: htaka@sapmed.ac.jp.
Abstract
BACKGROUND: The easy-to-calculate gender, age, and lung physiology (GAP) model shows good predictive and discriminative performance in the prognosis of idiopathic pulmonary fibrosis (IPF). However, the GAP model was not effective in predicting the prognosis accurately in previous Japanese and Korean IPF cohort studies. Therefore, we developed a modified GAP model for the East-Asian populations by weighing the GAP variables. The validity of the modified GAP model was subsequently evaluated in East-Asian IPF patients. METHODS: The derivation cohort comprised 326 patients with IPF. Weights of the variables were adjusted on the basis of coefficients derived from Cox regression models. The total points were distributed to the three stages of the disease so that the number of patients included in each stage was appropriate. The validity of the modified model was analyzed in another Japanese cohort of 117 patients with IPF and a nationwide cohort of Korean patients with IPF. RESULTS: Predicted survival rates differed significantly in the derivation cohort using the modified GAP model for each stage of IPF (log-rank test: stage I vs. stage II, p < 0.001; stage II vs. stage III, p < 0.001). Model performance improved according to Harrell's C-index (at three years: 0.696 in the original GAP model to 0.738 in the modified model). The performance of the modified model was validated in the Japanese validation and Korean national cohorts. CONCLUSIONS: Our modification of the original GAP model showed improved performance in East-Asian IPF patient populations.
BACKGROUND: The easy-to-calculate gender, age, and lung physiology (GAP) model shows good predictive and discriminative performance in the prognosis of idiopathic pulmonary fibrosis (IPF). However, the GAP model was not effective in predicting the prognosis accurately in previous Japanese and Korean IPF cohort studies. Therefore, we developed a modified GAP model for the East-Asian populations by weighing the GAP variables. The validity of the modified GAP model was subsequently evaluated in East-Asian IPF patients. METHODS: The derivation cohort comprised 326 patients with IPF. Weights of the variables were adjusted on the basis of coefficients derived from Cox regression models. The total points were distributed to the three stages of the disease so that the number of patients included in each stage was appropriate. The validity of the modified model was analyzed in another Japanese cohort of 117 patients with IPF and a nationwide cohort of Korean patients with IPF. RESULTS: Predicted survival rates differed significantly in the derivation cohort using the modified GAP model for each stage of IPF (log-rank test: stage I vs. stage II, p < 0.001; stage II vs. stage III, p < 0.001). Model performance improved according to Harrell's C-index (at three years: 0.696 in the original GAP model to 0.738 in the modified model). The performance of the modified model was validated in the Japanese validation and Korean national cohorts. CONCLUSIONS: Our modification of the original GAP model showed improved performance in East-Asian IPF patient populations.