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

Abstract

Purpose Similar to chronic obstructive pulmonary disease (COPD), the diffusing capacity of the lung (D LCO ) 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 D LCO and to assess the association between D LCO 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 D LCO into five groups based on spirometry: preserved spirometry, PRISm, mild COPD, moderate COPD, and severe/very severe COPD. The prevalence of low D LCO (< 80% per predicted) was compared among the five groups. Using PRISm patients with follow-up data, we further investigated the association of low D LCO with all-cause mortality. Results The prevalence of low D LCO 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-D LCO group than in the preserved-D LCO group ( P < 0.01). The multivariable-adjusted hazard ratio (HR) for all-cause mortality was significantly higher in the low-D LCO group than in the preserved-D LCO 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 D LCO was a significant risk factor for all-cause mortality. Clinicians should assess D LCO in the management of PRISm to predict the future risk of overall death.

The many faces of COPD in real life: a longitudinal analysis of the NOVELTY cohort

“…Instead, 13% had a normal spirometry (pre-COPD) and 14% PRISm (Figure 1). These figures are in the range of those reported previously in the general population [6,[10][11][12][13][14][15][16][17][18] or COPD patient cohorts [5,[19][20][21][22][23][24]. It is possible that other potential comorbidities (e.g., chronic heart failure / diastolic dysfunction) may mimic the symptoms of COPD and lead to an incorrect diagnosis; unfortunately, NOVELTY does not include any echocardiographic measurement that allow us to explore this possibility, albeit it may be of note that PRISm patients had a higher reported incidence of coronary artery disease (Table 1).…”

“…Several previous studies have investigated the characteristics and clinical relevance of pre-COPD and PRISm patients in the general population [6,[10][11][12][13][14][15][16][17][18] or in clinical cohorts of COPD patients [5,[19][20][21][22][23][24][25][26].…”

“…Our study has several strengths and limitations. Among the former: (1) while several of these observations have been reported in other cohorts, a clear strength of these findings is an unselected global population of subjects diagnosed with COPD, thereby supporting similar findings in selected cohorts (COPDGene [25], SPIROMICS [26,57]) in a more general population; (2) these data support the evolving concepts in the diagnosis of COPD, showing that a traditional spirometric cutoff of an FEV1/FVC <0.70 to support the diagnosis of COPD may not be necessary to diagnose (or rule out) COPD [58]; and, (3) this analysis provides novel and relevant data on the longitudinal stability of these diagnostic categories as well as about their relationship with clinically relevant outcomes, which has not been precisely defined by previous studies in other general population [6,[10][11][12][13][14][15][16][17][18] or clinical cohorts of patients with COPD [5,[19][20][21][22][23][24].…”

“…Previous studies in pre-COPD or PRISm patients have been conducted either in the general population [6,[10][11][12][13][14][15][16][17][18] or in clinical cohorts of COPD patient [5,[19][20][21][22][23][24][25][26], so their prevalence, characteristics, treatment, and temporal evolution in a real-life healthcare practice setting are unclear.…”

Clinical Manifestations of Subjects With the Non-Specific Pulmonary Function Test Pattern

“…There were no obvious survival difference signals between the obstructive and non-obstructive groups, but diffusing capacity was not included in this study. A low diffusing capacity has been shown to be a significant risk factor for all-cause mortality in subjects with PRISm 24 so including diffusing capacity in future NSP studies is necessary. In retrospect, using the updated GLI reference equations would have been reasonable and even more astute given the potential for misinterpretation of PFT results and the inaccuracies with the older equations.…”