Severe, eosinophilic asthma in primary care in Canada: a longitudinal study of the clinical burden and economic impact based on linked electronic medical record data

Abstract

BackgroundStratification of patients with severe asthma by blood eosinophil counts predicts responders to anti-interleukin (IL)-5 (mepolizumab and reslizumab) and anti-IL-5 receptor α (benralizumab) therapies. This study characterized patients with severe asthma who could qualify for these biologics in a primary care setting.MethodsWe retrospectively selected patients from July 1, 2010, to June 30, 2014, using a linked electronic medical records (EMR) database (IMS Evidence 360 EMR Canada) for > 950,000 patients in primary care in Ontario, Canada. Patients aged ≥ 12 years with ≥ 2 documented asthma diagnoses were identified as having severe asthma based on prescriptions for high-dosage inhaled corticosteroids (ICS) plus either a leukotriene receptor antagonist, long-acting β2-agonist (LABA), or theophylline filled on the same day. Patients’ asthma was considered severe also if they received a prescription for ICS with oral corticosteroids (OCS) or an additional prescription for omalizumab. Patient characteristics, asthma-related medications, and blood eosinophil counts were captured using observed care patterns for the year prior to ICS/LABA and/or OCS prescription. Health care resource use (HCRU) and costs were captured throughout the 1-year follow-up period.ResultsWe identified 212 patients who met the criteria for severe asthma. These patients required an average of 6.5 physician visits during the 1-year follow-up period (95% confidence interval 5.7–7.3), and 20 (9%) were referred to respiratory specialists. Overall, 56 patients (26%) with severe asthma had complete blood counts, of whom 23 (41%) had blood eosinophil counts ≥ 300 cells/μL and might be considered for anti-eosinophil therapies. Patients with severe asthma and blood eosinophil counts ≥ 300 cells/μL had more respiratory specialist referrals (17% vs. 12%) than patients with blood eosinophils < 300 cells/μL.ConclusionsOur data suggest that during 2010–2014, Ontario primary care patients with severe asthma and high blood eosinophil counts had greater HRCU than those with lower counts. Approximately 41% of patients with severe asthma could qualify for anti-eosinophil drugs based on blood eosinophil counts. However, the eosinophilic status of most patients was unknown. It is appropriate to increase awareness of the use of blood eosinophil counts to identify patients who could be considered for anti-eosinophil therapies.

Clinical profile of predefined asthma phenotypes in a large cohort of UK primary care patients (Clinical Practice Research Datalink)

“…Obese non-eosinophilic asthma held priority over atopic asthma as the former phenotype was deemed more specific. Phenotype groups were defined as follows: Benign asthma: low eosinophil counts on the latest blood test from April 2007 onward (<300 cells/µL45,46 and <4% of leukocytes), absence of SABA prescriptions and of severe exacerbations of asthma in the year before index date, and aged 40–60 years at study entry. The term “benign asthma” may not be accurate since even mild and/or under treated patients may have lung inflammation.…”

<p>Real-World Observational Study on the Characteristics and Treatment Patterns of Allergic Asthma Patients Receiving Omalizumab in Canada</p>

“…[29][30][31] The algorithm used for the current study was similar to one used in a previous study of severe eosinophilic asthma in primary care in Canada. 32 The study period is described in Figure 1. Patient index date was defined as the date of the patient's first omalizumab claim.…”

Short-term pulmonary infiltrate with eosinophilia caused by asthma: a phenotype of severe, eosinophilic asthma? Five cases and a review of the literature

“…Asthma is characterized by airway inflammation rich in eosinophils, and airway eosinophilia is associated with exacerbations and has been suggested to play a role in airway remodelling. However, severe eosinophilic asthma combined with pneumonia is rare [18], and cases of eosinophilic pneumonia caused by asthma itself have not been reported. Peripheral eosinophilia is often observed when tissue levels are elevated, but this is not as reliable a marker as tissue biopsy.…”