Tracking blood eosinophils over time: long-term trends in asthmatic patients from the COBRA cohort

In patients with asthma, long-term follow-up of blood eosinophil count (BEC) may be useful for identifying endotypes. The observational French COhort of BRonchial obstruction and Asthma (COBRA) study is an observational prospective multicenter cohort enrolling asthmatic patients.

To compare clinical characteristics according to BEC trajectories from inclusion to 2 ± 1 and 5 ± 2 years to assess their association with asthma outcomes.

Asthmatic patients were enrolled between January 12, 2007, and February 3, 2021. BECs were classified as persistently high if >300/μL at each time point, persistently low if <150/μL at each time point, or variable. Clinical variables and outcomes were analyzed according of BEC trajectories (persistently low vs high). The P values were corrected using the false discovery rate (FDR) method, and P values <.05 were considered as statistically significant.

Among the 389 patients with BEC data available at all 3 time points, 58 (15%) had persistently low BEC. No significant differences were observed regarding forced expiratory volume in 1 second (FEV₁), asthma control according to the Asthma Control Questionnaire 5, or exacerbations between patients with persistently high or low BEC. Forty-two patients with persistently high BEC were more likely to have nasal polyposis (43% vs 5%, FDR-corrected P value <.01) and higher IgE levels (median 283 UI/mL vs 72 UI/mL, FDR-corrected P value <.01). After adjustment for age, sex, smoking, and body mass index, persistently high BEC was associated with faster FEV₁ decline (odds ratio, 3.30; 95% confidence interval, 1.17-10; P = .03).

Patients from the COBRA cohort with persistently high BEC across a long-term follow-up were associated with a faster lung function decline.