The Prognostic Performance of Lung Diffusing Capacity in Preserved Ratio Impaired Spirometry: An Observational Cohort Study

Abstract

Hiroaki Ogata, Kachi Sha, Yasuaki Kotetsu, Aimi Enokizu-Ogawa, Katsuyuki Katahira, Akiko Ishimatsu, Kazuhito Taguchi, Atsushi Moriwaki, Makoto Yoshida Department of Respiratory Medicine, National Hospital Organization Fukuoka National Hospital, Fukuoka, JapanCorrespondence: Hiroaki Ogata, Department of Respiratory Medicine, National Hospital Organization Fukuoka National Hospital, 4-39-1 Yakatabaru, Minami-ku, Fukuoka, 811-1394, Japan, Tel [phone], Fax [phone], Email [email protected]: Similar to chronic obstructive pulmonary disease (COPD), the diffusing capacity of the lung (DLCO) might be decreased and associated with poor prognosis in preserved ratio impaired spirometry (PRISm), a clinical entity as a prodromal phase of COPD. The aims of the present study were to evaluate the distributions of DLCO and to assess the association between DLCO and mortality among subjects with PRISm.Patients and Methods: We conducted an observational cohort study at the National Hospital Organization Fukuoka National Hospital. We classified the 899 patients ≥ 40 years of age with an assessment of DLCO into five groups based on spirometry: preserved spirometry, PRISm, mild COPD, moderate COPD, and severe/very severe COPD. The prevalence of low DLCO (< 80% per predicted) was compared among the five groups. Using PRISm patients with follow-up data, we further investigated the association of low DLCO with all-cause mortality.Results: The prevalence of low DLCO in the PRISm group (58.8%) was significantly higher than that in the preserved-spirometry group (21.8%), the mild-COPD group (23.5%), and the moderate-COPD group (36.0%) (all P < 0.01), and it was comparable to that in the severe/very severe-COPD group (63.2%). The results remained unchanged after adjusting for potential confounders. Among the PRISm subjects, the overall survival rate was significantly lower in the low-DLCO group than in the preserved-DLCO group (P < 0.01). The multivariable-adjusted hazard ratio (HR) for all-cause mortality was significantly higher in the low-DLCO group than in the preserved-DLCO group (HR = 10.10 (95% confidence interval 2.33– 43.89)).Conclusion: Diffusing capacity was more impaired in PRISm subjects than in those with preserved spirometry or mild to moderate COPD. Regarding PRISm, low DLCO was a significant risk factor for all-cause mortality. Clinicians should assess DLCO in the management of PRISm to predict the future risk of overall death.Keywords: preserved ratio impaired spirometry, chronic obstructive pulmonary disease, diffusing capacity of the lungs, all-cause mortality

Keywords

• preserved ratio impaired spirometry
• chronic obstructive pulmonary disease
• diffusing capacity of the lungs
• all-cause mortality