Serial blood eosinophils and clinical outcome in patients with chronic obstructive pulmonary disease

Abstract

BackgroundBlood eosinophils have been suggested as a potential biomarker in chronic obstructive pulmonary disease (COPD), and their stability over time has been investigated in a few studies. However, the association between the stability of blood eosinophils and long-term clinical outcomes in COPD patients has yet to be fully elucidated. This study aimed to evaluate the stability of blood eosinophils and its association with clinical outcomes in COPD patients.MethodsIn total, 299 COPD patients from the Korean Obstructive Lung Disease cohort with at least two blood eosinophil measurements were included. Patients were stratified according to a cut-off of 300 cells/μL, and the association between eosinophil changes and all-cause mortality was analysed. The annual decline in forced expiratory volume in 1 s (FEV1), serial changes in St George’s Respiratory Questionnaire score (SGRQ), and exacerbations during follow-up were compared among eosinophil groups.ResultsPatients were stratified into three groups according to the blood eosinophil cut-off: persistently < 300 cells/μL (PL; n = 175), variable (V; n = 68), and persistently ≥300 cells/μL (PH; n = 56). There were no significant differences in baseline characteristics (age, sex, smoking, body mass index, use of inhaled corticosteroids, exacerbations in the previous year, FEV1 (L or % predicted), or emphysema score) among the groups. During a median follow-up of 6.0 years, the PH group had a better survival rate than the PL group (adjusted mortality rate ratio, 0.29; 95% confidence interval, 0.09–0.97; P = 0.045). The PH group also showed improved symptoms and impact domains of SGRQ score compared to the PL group. No difference was found in annual FEV1 decline or exacerbations during follow-up among the groups.ConclusionsPatients with persistently high blood eosinophils had a better survival rate than those with persistently low blood eosinophils. Serial follow-up of blood eosinophils could help to predict outcomes in COPD patients.Electronic supplementary materialThe online version of this article (10.1186/s12931-018-0840-x) contains supplementary material, which is available to authorized users.

Blood eosinophils could be useful as a biomarker in chronic obstructive pulmonary disease exacerbations

“…More than one‐third (39.1%) of our patients have a BEC greater than 200, which is lower than the 49.4% mentioned by Hastie et al, as well as the 63.7% of the patients by Disantoestefano . Using the 300 cells/µL cut‐off point, 22.1% are equal or greater, similar to that referred to by Watz or Roche, but lower than other populations where these values increase between 32.5% and 41.4% . The results are more similar with a cut‐off point of 400 cells/µL, as 11.2% of our patients equal or exceed this figure, similar to the 11% mentioned by Watz et al, or to the 14.4% in the study by Disantoestefano …”

“…On analysing these results mentioned by other authors, in most publications it is mentioned that the exacerbation rate and/or hospital admissions are not changed in relation to the BEC, with some studies showing more exacerbations with higher BEC and others less exacerbations with a lower BEC …”

“…Other authors have also not observed any relationship between the eosinophil levels in blood with mortality because of the COPD exacerbation, although the most common is that low levels of eosinophils in blood may be associated with a higher mortality …”

“…In our case, they are patients who require hospital admission, with a mean age of 74 years, with 79.1% being males. The majority of authors included a younger population, with a mean age of between 64 and 72 years, and a lower percentage of males, which in few cases exceed 60% of the patients included . Other authors include patients after a hospital admission, as in our case, others from chest disease clinics, or a general population …”

“…It has also been evaluated as a prognostic indicator in these patients, with the results being divergent in both cases. Considering mortality, the authors did not observe differences with respect to the BEC, and others mention a lower mortality with a higher BEC . On analysing the exacerbations, most authors did not observe any differences with respect to the BEC, although some do refer to a higher overall incidence with an elevated BEC, but less mild exacerbations …”