Asthma phenotyping in primary care: another step towards personalized medicine
Published: August 14, 2021
Severe asthma consists of different phenotypes that differ in their clinical presentation, underlying pathways and response to treatment.1 The Global Initiative for Asthma (GINA) strategy for asthma diagnosis and management notes that most patients with asthma have Type 2 inflammation, which is characterized by raised eosinophils and can be treated with targeted treatments such as biologic therapies.2 Therefore, the International Severe Asthma Registry (ISAR) eosinophil phenotype gradient algorithm was developed by expert consensus; it was observed that 92.1% of severe asthma patients globally were most likely or likely eosinophilic, and only 1.6% of patients were non-eosinophilic.3 In primary care, asthma phenotypes are less well-characterized.
In a historical cohort study by Kerkhof and colleagues, recently published in The Journal of Allergy and Clinical Immunology: In Practice, the ISAR eosinophil phenotype gradient algorithm was applied to UK primary care patients from the Optimum Patient Care Research Database (OPCRD) and the Clinical Practice Research Datalink. These databases were selected as they have unique characteristics to enable such studies. For instance, OPCRD comprises electronic medical records including laboratory results for >14 million patients with a median time in the database of 19.8 years; the majority of patients have significant diagnostic data (e.g., asthma onset) from birth. Patients aged ≥13 years with active asthma and at least one blood eosinophil count recording were included in the study and were classified according to the likelihood of eosinophilic phenotype using the ISAR algorithm. Demographic, clinical and healthcare resource utilization (HCRU) characteristics were described for each phenotype.
The eosinophilic phenotype was predominant across all asthma severities in UK primary care; 72.5% of patients had most likely or likely eosinophilic phenotypes and just 5.6% of patients were non-eosinophilic. Patients with eosinophilic asthma tended to have more comorbidities; 28.2% of patients who were most likely eosinophilic versus 6.9% of patients who were non-eosinophilic had a Charlson comorbidity index score of ≥2. These comorbidities included Type 2 comorbidities (e.g., eczema, allergic rhinitis, chronic rhinosinusitis with and without nasal polyps) and steroid-related adverse events (e.g., gastroesophageal reflux disease, diabetes, cardiovascular disease, anxiety or depression, etc.). Furthermore, the eosinophilic phenotype was associated with greater likelihood of exacerbations; 24.8% of patients with most likely eosinophilic asthma versus 15.3% of patients with non-eosinophilic asthma experienced ≥1 asthma attack. Finally, patients with most likely eosinophilic asthma had greater HCRU than those with non-eosinophilic asthma (e.g., 10.8 versus 7.9 general practitioner all-cause consultations per year).
Asthma eosinophilic phenotyping should become part of routine clinical practice in primary care, since patients with eosinophilic asthma phenotypes may benefit from Type 2-targeted treatments such as inhaled corticosteroids and steroid-sparing biologics.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.