Yasuhiro Kondoh1, Hiroyuki Taniguchi1, Kensuke Kataoka1, Taiki Furukawa1, Masahiko Ando2, Kenta Murotani3, Michiaki Mishima4, Yoshikazu Inoue5, Takashi Ogura6, Masashi Bando7, Koichi Hagiwara8, Takafumi Suda9, Hirofumi Chiba10, Hiroki Takahashi10, Yukihiko Sugiyama7, Sakae Homma11. 1. Department of Respiratory Medicine and Allergy, Tosei General Hospital, Seto, Japan. 2. Center for Advanced Medicine and Clinical Research, Nagoya University Hospital, Nagoya, Japan. 3. Division of Biostatistics, Clinical Research Center Aichi Medical University, Nagakute, Japan. 4. Department of Respiratory Medicine, Kyoto University Hospital, Kyoto, Japan. 5. Department of Diffuse Lung Diseases and Respiratory Failure, Clinical Research Centre, National Hospital Organization Kinki-Chuo Chest Medical Centre, Sakai, Japan. 6. Department of Respiratory Medicine, Kanagawa Cardiovascular and Respiratory Center, Yokohama, Japan. 7. Division of Pulmonary Medicine, Department of Medicine, Jichi Medical University, Shimono, Japan. 8. Department of Comprehensive Medicine 1, Saitama Medical Center, Jichi Medical University, Moroyama, Japan. 9. Second Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, Japan. 10. Third Department of Internal Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan. 11. Department of Respiratory Medicine, Toho University Omori Medical Center, Shimotsuke, Japan.
Abstract
BACKGROUND AND OBJECTIVE: In Japan, the classification of disease severity of idiopathic pulmonary fibrosis (IPF) (J-system) has been used in making decisions on medical care subsidies. The present J-system consists of arterial partial pressure of oxygen (PaO2 ) and exercise desaturation in stages of I-IV. It provides a good prognostic classification in stages III and IV, but not in stages I and II. Therefore, we propose a revised system to improve discriminative ability in stages I and II. METHODS: We compared the revised J-system with the present J-system using Cox proportional hazards model to predict mortality rate. We also evaluated the recently proposed GAP (Gender, Age and Physiology) system in comparison to both J-systems. RESULTS: Two-hundred and fifteen IPF patients were studied retrospectively. A univariate model showed that the present and revised J-systems and a modified GAP system were all significant prognostic factors. The C-statistic for discriminating prognosis was higher in the revised J-system than the modified GAP system and the present J-system (0.677, 0.652 and 0.659, respectively). The C-statistics of these models produced from the 10 000 bootstrap samples were similar to those of the original models, suggesting good internal validation (0.665 (95% CI: 0.621-0.705), 0.645 (0.600-0.686) and 0.659 (0.616-0.700), respectively). Multivariate analysis revealed that the revised J-system (P = 0.0038) and the modified GAP system (P = 0.0029) were independent prognostic factors. CONCLUSION: The revised J-system can provide a better mortality prediction than the present one. Both the revised J-system and the modified GAP system are independent and valuable tools for prognostication and clinical management for IPF.
BACKGROUND AND OBJECTIVE: In Japan, the classification of disease severity of idiopathic pulmonary fibrosis (IPF) (J-system) has been used in making decisions on medical care subsidies. The present J-system consists of arterial partial pressure of oxygen (PaO2 ) and exercise desaturation in stages of I-IV. It provides a good prognostic classification in stages III and IV, but not in stages I and II. Therefore, we propose a revised system to improve discriminative ability in stages I and II. METHODS: We compared the revised J-system with the present J-system using Cox proportional hazards model to predict mortality rate. We also evaluated the recently proposed GAP (Gender, Age and Physiology) system in comparison to both J-systems. RESULTS: Two-hundred and fifteen IPF patients were studied retrospectively. A univariate model showed that the present and revised J-systems and a modified GAP system were all significant prognostic factors. The C-statistic for discriminating prognosis was higher in the revised J-system than the modified GAP system and the present J-system (0.677, 0.652 and 0.659, respectively). The C-statistics of these models produced from the 10 000 bootstrap samples were similar to those of the original models, suggesting good internal validation (0.665 (95% CI: 0.621-0.705), 0.645 (0.600-0.686) and 0.659 (0.616-0.700), respectively). Multivariate analysis revealed that the revised J-system (P = 0.0038) and the modified GAP system (P = 0.0029) were independent prognostic factors. CONCLUSION: The revised J-system can provide a better mortality prediction than the present one. Both the revised J-system and the modified GAP system are independent and valuable tools for prognostication and clinical management for IPF.