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

Defining clinical subtypes of adult asthma using electronic health records: Analysis of a large UK primary care database with external validation

INTRODUCTION

Asthma is one of the commonest chronic conditions in the world. Subtypes of asthma have been defined, typically from clinical datasets on small, well-characterised subpopulations of asthma patients. We sought to define asthma subtypes from large longitudinal primary care electronic health records (EHRs) using cluster analysis.

METHODS

In this retrospective cohort study, we extracted asthma subpopulations from the Optimum Patient Care Research Database (OPCRD) to robustly train and test algorithms, and externally validated findings in the Secure Anonymised Information Linkage (SAIL) Databank. In both databases, we identified adults with an asthma diagnosis code recorded in the three years prior to an index date. Train and test datasets were selected from OPCRD using an index date of Jan 1, 2016. Two internal validation datasets were selected from OPCRD using index dates of Jan 1, 2017 and 2018. Three external validation datasets were selected from SAIL using index dates of Jan 1, 2016, 2017 and 2018. Each dataset comprised 50,000 randomly selected non-overlapping patients. Subtypes were defined by applying multiple correspondence analysis and k-means cluster analysis to the train dataset, and were validated in the internal and external validation datasets.

RESULTS

We defined six asthma subtypes with clear clinical interpretability: low inhaled corticosteroid (ICS) use and low healthcare utilisation (30% of patients); low-to-medium ICS use (36%); low-to-medium ICS use and comorbidities (12%); varied ICS use and comorbid chronic obstructive pulmonary disease (4%); high (10%) and very high ICS use (7%). The subtypes were replicated with high accuracy in internal (91-92%) and external (84-86%) datasets.

CONCLUSION

Asthma subtypes derived and validated in large independent EHR databases were primarily defined by level of ICS use, level of healthcare use, and presence of comorbidities. This has important clinical implications towards defining asthma subtypes, facilitating patient stratification, and developing more personalised monitoring and treatment strategies.

Glutathione S-Transferase Gene Associations and Gene-Environment Interactions for Asthma

PURPOSE OF REVIEW

Asthma is one of the most common chronic inflammatory airway diseases. Airway oxidative stress is defined as an imbalance between oxidative and antioxidative processes in the airways. There is evidence that chronic damage caused by oxidative stress may be involved in asthmatic inflammation and reduced lung function. Given their biological antioxidant function, the antioxidant genes in the glutathione S-transferase (GST) family are believed to be associated with development and progression of asthma. This review aims to summarize evidence on the relationship between GST gene polymorphisms and asthma and interactions with environmental exposures.

RECENT FINDINGS

The current evidence on the association between GST genes and asthma is still weak or inconsistent. Failure to account for environmental exposures may explain the lack of consistency. It is highly likely that environmental exposures interact with GST genes involved in the antioxidant pathway. According to current knowledge, carriers of GSTM1(rs366631)/T1(rs17856199) null genotypes and GSTP1 Val105 (rs1695) genotypes are more susceptible to environmental oxidative exposures and have a higher risk of asthma. Some doubt remains regarding the presence or absence of interactions with different environmental exposures in different study scenarios. The GST-environment interaction may depend on exposure type, asthma phenotype or endotype, ethnics, and other complex gene-gene interaction. Future studies could be improved by defining precise asthma endotypes, involving multiple gene-gene interactions, and increasing sample size and power. Although there is evidence for an interaction between GST genes, and environmental exposures in relation to asthma, results are not concordant. Further investigations are needed to explore the reasons behind the inconsistency.

Using routinely collected primary care records to identify and investigate severe asthma: a scoping review

Shielding during the coronavirus pandemic has highlighted the potential of routinely collected primary care records to identify patients with 'high-risk' conditions, including severe asthma. We aimed to determine how previous studies have used primary care records to identify and investigate severe asthma and whether linkage to other data sources is required to fully investigate this 'high-risk' disease variant. A scoping review was conducted based on the Arksey and O'Malley framework. Twelve studies met all criteria for inclusion. We identified variation in how studies defined the background asthma cohort, asthma severity, control and clinical outcomes. Certain asthma outcomes could only be investigated through linkage to secondary care records. The ability of primary care records to represent the entire known asthma population is unique. However, a number of challenges need to be overcome if their full potential to accurately identify and investigate severe asthma is to be realised.

Data-driven questionnaire-based cluster analysis of asthma in Swedish adults

The aim of this study was to identify asthma phenotypes through cluster analysis. Cluster analysis was performed using self-reported characteristics from a cohort of 1291 Swedish asthma patients. Disease burden was measured using the Asthma Control Test (ACT), the mini Asthma Quality of Life Questionnaire (mini-AQLQ), exacerbation frequency and asthma severity. Validation was performed in 748 individuals from the same geographical region. Three clusters; early onset predominantly female, adult onset predominantly female and adult onset predominantly male, were identified. Early onset predominantly female asthma had a higher burden of disease, the highest exacerbation frequency and use of inhaled corticosteroids. Adult onset predominantly male asthma had the highest mean score of ACT and mini-AQLQ, the lowest exacerbation frequency and higher proportion of subjects with mild asthma. These clusters, based on information from clinical questionnaire data, might be useful in primary care settings where the access to spirometry and biomarkers is limited.

Treatment patterns among non-active users of maintenance asthma medication in the United Kingdom: a retrospective cohort study in the Clinical Practice Research Datalink

Objective: To describe patient characteristics, treatment patterns and healthcare utilization (HCU) of non-active users of maintenance asthma medications in the United Kingdom.Methods: Retrospective, cohort analysis of patients with asthma, aged ≥ 6 years who were non-active users of maintenance therapy (no prescription for inhaled corticosteroids (ICS), combined ICS/long-acting beta agonists (ICS/LABA) or 'other' bronchodilatory therapies in last 12 months) were identified in the Clinical Practice Research Datalink (2012-2015) and followed-up for 2 years after a new prescription for an asthma maintenance medication (index date). Patient characteristics, most common maintenance treatment sequences and HCU were described.Results: 55,293 patients were identified (ICS: 46,297, ICS/LABA: 8,367; Other: 629). Mean age was 37 years and 56% were female. During follow-up, the most common treatment sequences across groups implied intermittent use, comprising periods of maintenance therapy interspersed with maintenance-free periods. During year 1 and year 2 of follow-up, the proportion of patients prescribed OCS was 19% and 13%, prescribed ≥ 4 short-acting bronchodilators (SABD) was 24% and 19%, having ≥ 3 asthma-related primary care consultations/year was 59% and 36% and experiencing ≥ 1 exacerbation/year was 15% and 11%, respectively.Conclusions: In previously non-active users of asthma maintenance medication subsequently commenced on maintenance therapy, intermittent use was common during the 2-year follow-up despite the potential need for regular use as evidenced by patient HCU and SABD usage patterns. This highlights the need for regular patient assessment and education on medication adherence to ensure appropriateness of prescribing to maintain asthma control.