Elevated Blood Eosinophil Count Reduced Asthma-Related Readmissions

Francisco-Javier Gonzalez-Barcala, MD, PhD

A study of 1316 patients with asthma admitted to the University Hospital of Santiago de Compostela in Spain has determined a positive link between elevated blood eosinophil count (BEC) and lower incidence of asthma hospital readmissions.

The lead author Francisco-Javier Gonzalez-Barcala, MD, PhD, with the Department of Medicine at the University of Santiago de Compostela and Spain's Biomedical Research Networking Center (CIBERES), wrote that the study was designed to "analyze the relationship between the BEC levels and hospital readmissions in patients with asthma."

If the study results can be corroborated by further research, there may be a shift away from more expensive traditional testing methods for asthma severity and treatment outcomes and towards the blood eosinophil counts.

Gonzalez-Barcala and colleagues state that although the "presence of eosinophils in asthma inflammation is a relevant factor in the pathophysiology of the disease" and BEC has proven useful as a biomarker to identify and predict treatment response in some patients (particularly those receiving corticosteroid treatment for asthma), the relationship between the BEC and asthma severity is still unclear. The blood eosinophil count, the study points out, is "not a marker of severity in all asthmatic patients" and the usefulness of the BEC as a consideration in the management of asthma remains contested and controversial due to mixed results in previous studies.

The problem with the sputum eosinophil count (SEC), according to the study, is the complexity and cost associated with SEC testing. Gonzalez-Barcala writes that due to the complexity and cost of the SEC determination "it is not available in all health centers," and this limited availability, combined with prohibitive cost, can affect patients.

In contrast to the SEC determination, the BEC determination is available at a lower cost in a wider range of healthcare and clinical testing facilities. If the BEC determination is proven to be an effective indicator of the management of asthma, as other recent studies have suggested, then the switch to using BEC determination could provide better quality of care for patients while reducing health care costs.

In order to better analyze the relationship between the BEC levels and asthma severity, Gonzalez-Barcala and colleagues used hospital readmissions as an indicator of asthma severity and frequency. The retroactive review collected 10 years of admissions/readmissions data on patients (age ≥18) due to exacerbation of asthma.

The study included 1316 patients in total (mean age = 60 years). Data on overall health, demographics, comorbidities, baseline severity of asthma (according to 2006 Global Initiative for Asthma criteria), asthma personal history, all testing, emergency department (ED) visits and length of hospital stay were collected through examination of clinical records.

Gonzalez-Barcala and colleagues state that "the BEC was determined from the first blood sample taken from the patient after their arrival at the hospital" and "readmissions were analyzed using 4 cut-off points; less than 150 eosinophils/μL vs ≥150/ μL, less than 200 vs 200/μL, less than 300 vs ≥300/μL, and less than 400 vs ≥400/μL." Readmissions were classified into 2 groups: early readmission (ER)(≤15 days after hospital discharge) and late readmission (LR)(≥16 days after hospital discharge).

Data showed the mean BEC for patients (70% female, 30% male) was 201.7 cells/μL; a BEC of ≥300 was found in 23% of patients (n= 274) and ≥400 was found in 16% of patients (n= 184). Readmission data for 1170 patients showed that 21% of patients had a LR, and 1.4% had an ER. The study ultimately determined that elevated BEC was associated with a lower risk of LR in patients. Researchers confirmed that a BEC ≥300 cells/μL showed a reduction of risk of LR of 42%, a BEC ≥400 cells/μL showed a reduction in LR risk of 41% and decrease in FLR [frequent late readmissions] of 63%."

The results of the study, Gonzalez-Barcala points out, are in line with some previous studies on the BEC and asthma severity, but directly opposed to others; he attributes this variation in results to differences in sample size and methodologies. Another cause for the discrepancies between different studies, Gonzalez-Barcala writes, could center on "the combination of different biomarkers" which, if identified, might "improve the ability to identify inflammatory phenotypes."

Although further studies are necessary to end the debate over the usefulness of the BEC in predicting asthma severity and outcomes, the study concludes that there is an apparent link between elevated BEC and lower risk of future acute asthma attacks or exacerbations. If the study results can be corroborated, then low-cost, high-availability BEC determination testing could become a useful diagnostic for determining treatment and maintaining control of asthma in patients.

The article, "Association between blood eosinophil count with asthma hospital readmissions" appears in the July 2018 issue of the European Journal of Internal Medicine.