Relationship between the respiratory microbiome and the severity of airflow limitation, history of exacerbations and circulating eosinophils in COPD patients.

BACKGROUND: The respiratory microbiome is altered in COPD patients but its relationship with core components of the disease, such as the severity of airflow limitation, the frequency of exacerbations or the circulating levels of eosinophils, is unclear. METHODS: Cross-sectional study comprising 72 clinically stable COPD patients (mean age 68 [SD 7.9] years; FEV1 48.7 [SD 20.1]% of reference) who provided spontaneous sputum samples for 16S rRNA gene amplification and sequencing. The microbiome composition was analysed with QIIME. RESULTS: We observed that: (1) more severe airflow limitation was associated with reduced relative abundance (RA) of Treponema and an increase in Pseudomonas; (2) patients with ≥2 exacerbations the previous year showed a significantly different bacterial community with respect to non-exacerbators (p = 0.014), with changes in 13 genera, including an increase of Pseudomonas, and finally, (3) peripheral eosinophils levels ≥2% were associated with more diverse microbiome [Chao1 224.51 (74.88) vs 277.39 (78.92) p = 0.006; Shannon 3.94 (1.05) vs 4.54 (1.06) p = 0.020], and a significant increase in the RAs of 20 genera. CONCLUSION: The respiratory microbiome in clinically stable COPD patients varies significantly according to the severity of airflow limitation, previous history of exacerbations and circulating eosinophils levels.

Predictors of one-year mortality after hospitalization for an exacerbation of COPD.

BACKGROUND: Hospitalization for a severe exacerbation of COPD (eCOPD) is an important event in the natural history of COPD. Identifying factors related to mortality 1 year after hospitalization could help determine interventions to reduce mortality. METHODS: In a prospective, observational, multicentre study, we evaluated data from two cohorts: the Spanish audit of hospital COPD exacerbation care (our derivation sample) and the Spanish cohort of the European audit of COPD exacerbation care (our validation sample). The endpoint was all-cause mortality. Mortality was determined by local research managers of the participating hospitals and matched the official national index records in Spain. RESULTS: In the multivariate analysis, factors independently related to an increase in mortality were older age, cardio-cerebro-vascular and/or dementia comorbidities, PaCO2 > 55 mmHg measured at emergency department arrival, hospitalizations for COPD exacerbations in the previous year, and hospital characteristics. The area under the receiver-operating curve for this model was 0.75 in the derivation cohort and 0.76 in the validation cohort. CONCLUSION: One-year mortality following the index hospitalization for an exacerbation of COPD was related to clinical characteristics of the patient and of the index event, previous events of similar severity, and characteristics of the hospital where the patient was treated.