In chronic obstructive pulmonary disease (COPD), the risk for future exacerbations is linked to high sputum neutrophil proportions and significant air trapping, according to a study in BMJ Open Respiratory Research.
Investigators sought to assess associations between sputum neutrophil proportions and future COPD exacerbations as well as to determine whether these associations were affected by significant air trapping. The researchers therefore conducted the Early Chronic Obstructive Pulmonary Disease (ECOPD) study, a prospective, observational study of participants aged 40 to 80 years in Guangzhou, Shaoguan, and Heyuan, Guangdong, China. Baseline data, obtained from July 2019 to August 2021, included demographic data, tobacco smoking history, medical history, spirometric values, induced sputum data, and computed tomography (CT) chest scans. Prospective exacerbation data were obtained after the first year of follow-up, and the longitudinal follow-up data were collected in August 2022.
The study analysis included 582 patients with COPD and an induced sputum sample at baseline. The initial year of follow-up was completed by 521 (89.5%) patients. A total of 287 patients (mean [SD] age, 63.8 [6.6] years; 94% male) had low levels of sputum neutrophil proportions (<86.2%), and 295 patients (mean age, 65.7 [8.0] years; 95% male) had high levels of sputum neutrophil proportions (≥86.2%).
The patients with high levels of sputum neutrophil proportions had an increased risk for severe exacerbation (odds ratio [OR] 1.68; 95% CI, 1.09-2.62; P =.020) compared with participants with low levels of sputum neutrophil proportions. In the air trapping group, the patients with high levels of sputum neutrophil proportions had increased risk for acute exacerbation (OR 1.69; 95% CI, 1.01-2.84; P =.046) and severe exacerbation (OR 1.79; 95% CI, 1.03-3.15; P =.042) compared those with low levels.
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Chronic obstructive pulmonary disease (COPD) patients with high sputum neutrophil proportions and significant air trapping are at risk of future exacerbation in COPD, especially severe exacerbation and frequent exacerbation.
After the initial year of follow-up, a greater percentage of severe exacerbation was seen in the high neutrophil/air trapping (HN/AT) group vs the low neutrophil/non-air trapping (LN/NA) group (16.0% vs 31.9%, P = .010). No significant differences were found in exacerbation frequency levels between the 4 cohorts — ie, the LN/NA group, high neutrophil/non-air trapping (HN/NA) group, low neutrophil/air trapping (LN/AT) group, and the HN/AT group (P =.105).
In multivariable logistic regression, patients in the HN/AT group had an increased OR for severe exacerbation (OR 2.72; 95% CI, 1.42 to 5.43; P =.003) compared with the LN/ NA group. The HN/AT group had a greater risk for frequent exacerbation vs the LN/NA group (OR 3.29; 95% CI, 1.30-9.37; P =.017). No significant differences in severe exacerbation and frequent exacerbation were observed in a comparison of the HN/NA group or LN/AT groups with the LN/NA group.
The investigators noted that the ECOPD study used patient-reported outcomes to assess the incidence of acute exacerbation, and sufficient data on sputum induction were obtained from 63.6% of patients with COPD, which was lower than those in the entire population of the ECOPD study (80.6%). Furthermore, the patients primarily had mild to moderate disease status (86.9%), which could have introduced selection bias.
“Chronic obstructive pulmonary disease (COPD) patients with high sputum neutrophil proportions and significant air trapping are at risk of future exacerbation in COPD, especially severe exacerbation and frequent exacerbation,” the study authors concluded. “Our findings encourage the use of sputum neutrophils and CT-based air trapping in clinical practice for precise treatments in clinical intervention.”
