Search

BACKGROUND: There is a lack of mechanism-driven, clinically relevant biomarkers in chronic obstructive pulmonary disease (COPD). Mitochondrial dysfunction, a proposed disease mechanism in COPD, is associated with the release of mitochondrial DNA (mtDNA), but plasma cell-free mtDNA has not been previously examined prospectively for associations with clinical COPD measures. METHODS: P-mtDNA, defined as copy number of mitochondrially-encoded NADH dehydrogenase-1 (MT-ND1) gene, was measured by real-time quantitative PCR in 700 plasma samples from participants enrolled in the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) cohort. Associations between p-mtDNA and clinical disease parameters were examined, adjusting for age, sex, smoking status, and for informative loss to follow-up. RESULTS: P-mtDNA levels were higher in participants with mild or moderate COPD, compared to smokers without airflow obstruction, and to participants with severe COPD. Baseline increased p-mtDNA levels were associated with better CAT scores in female smokers without airflow obstruction and female participants with mild or moderate COPD on 1-year follow-up, but worse 6MWD in females with severe COPD. Higher p-mtDNA levels were associated with better 6MWD in male participants with severe COPD. These associations were no longer significant after adjusting for informative loss to follow-up. CONCLUSION: In this study, p-mtDNA levels associated with baseline COPD status but not future changes in clinical COPD measures after accounting for informative loss to follow-up. To better characterize mitochondrial dysfunction as a potential COPD endotype, these results should be confirmed and validated in future studies. TRIAL REGISTRATION:  ClinicalTrials.gov NCT01969344 (SPIROMICS).

Levels of iron and iron-related proteins including ferritin are higher in the lung tissue and lavage fluid of individuals with chronic obstructive pulmonary disease (COPD), when compared to healthy controls. Whether more iron in the extracellular milieu of the lung associates with distinct clinical phenotypes of COPD, including increased exacerbation susceptibility, is unknown. We measured iron and ferritin levels in the bronchoalveolar lavage fluid (BALF) of participants enrolled in the SubPopulations and InteRmediate Outcome Measures In COPD (SPIROMICS) bronchoscopy sub-study (n = 195). BALF Iron parameters were compared to systemic markers of iron availability and tested for association with FEV1 % predicted and exacerbation frequency. Exacerbations were modelled using a zero-inflated negative binomial model using age, sex, smoking, and FEV1 % predicted as clinical covariates. BALF iron and ferritin were higher in participants with COPD and in smokers without COPD when compared to non-smoker control participants but did not correlate with systemic iron markers. BALF ferritin and iron were elevated in participants who had COPD exacerbations, with a 2-fold increase in BALF ferritin and iron conveying a 24% and 2-fold increase in exacerbation risk, respectively. Similar associations were not observed with plasma ferritin. Increased airway iron levels may be representative of a distinct pathobiological phenomenon that results in more frequent COPD exacerbation events, contributing to disease progression in these individuals.

Background: Observational studies suggest that some patients meeting criteria for ARDS no longer fulfill the oxygenation criterion early in the course of their illness. This subphenotype of rapidly improving ARDS has not been well characterized. We attempted to assess the prevalence, characteristics, and outcomes of rapidly improving ARDS and to identify which variables are useful to predict it.Methods: A secondary analysis was performed of patient level data from six ARDS Network randomized controlled trials. We defined rapidly improving ARDS, contrasted with ARDS > 1 day, as extubation or a Pao2 to Fio2 ratio (Pao2:Fio2) > 300 on the first study day following enrollment.Results: The prevalence of rapidly improving ARDS was 10.5% (458 of 4,361 patients) and increased over time. Of the 1,909 patients enrolled in the three most recently published trials, 197 (10.3%) were extubated on the first study day, and 265 (13.9%) in total had rapidly improving ARDS. Patients with rapidly improving ARDS had lower baseline severity of illness and lower 60-day mortality (10.2% vs 26.3%; P < .0001) than ARDS > 1 day. Pao2:Fio2 at screening, change in Pao2:Fio2 from screening to enrollment, use of vasopressor agents, Fio2 at enrollment, and serum bilirubin levels were useful predictive variables.Conclusions: Rapidly improving ARDS, mostly defined by early extubation, is an increasingly prevalent and distinct subphenotype, associated with better outcomes than ARDS > 1 day. Enrollment of patients with rapidly improving ARDS may negatively affect the prognostic enrichment and contribute to the failure of therapeutic trials. [ABSTRACT FROM AUTHOR]