Preventing Unscheduled Hospitalisations from Asthma: a retrospective cohort study using routine primary and secondary care data in the UK (The PUSH-Asthma Study)

Date of Approval
Application Number
Technical Summary

Study design:
A retrospective cohort study.

Primary exposure:
A coded diagnosis of asthma.

Primary outcome: Asthma-related hospital admissions.

Secondary outcomes: prescriptions of short courses of oral corticosteroids (OCS), asthma-related high dependency unit (HDU) admissions, asthma-related intensive care unit (ICU) admissions, composite outcome including HDU and ICU admissions, and a composite outcome including asthma-related hospital admissions and prescriptions of OCS.

Prescriptions of OCS are a proxy indicator of asthma exacerbations.
The composite outcomes will increase the power of the study and precision of the estimated effect size.

We will establish a cohort of asthma patients with linked Hospital Episode Statistics (HES) data in CPRD which will be used to determine hospital admissions for asthma exacerbations.

The cohort will be stratified into the following age-groups: 5-11, 12-17, 18+ years. We will describe the demographic and clinical characteristics of patients such as age, sex, and comorbidities. We will determine the incidence of asthma-related hospital admissions and quantify the association between proposed risk factors and number of asthma-related hospital admissions using a Poisson regression model. We will phenotype patients with an asthma-related hospital admission using cluster analyses.

We will externally validate existing risk prediction models for asthma exacerbations as a separate analysis using the extracted CPRD data from this study: these models will be identified from the existing literature and recent systematic reviews. We will also externally validate a novel risk prediction model in CPRD Aurum, developed by the University of Edinburgh. Assessing the performance of existing models will allow for the identification of the most promising models to be prospectively evaluated in randomised controlled impact trials and provide evidence for potential use in primary care.

We will assess the primary care management of patients after discharge from hospital following an asthma exacerbation, such as medication changes, smoking cessation advice and self-management plans.

Health Outcomes to be Measured

(1) Number of hospital admissions for asthma
(2) Prescriptions of short courses of oral corticosteroids for asthma exacerbations
(3) Number of high dependency unit (HDU) admissions for asthma exacerbations
(4) Number of intensive care unit (ICU) admissions for asthma exacerbations
(5) A composite measure including HDU and ICU admissions for asthma exacerbations
(6) A composite measure including hospital admissions for asthma exacerbations and prescriptions of short courses of oral corticosteroids
(7) Delivery of clinical care management for asthma after discharge from hospital (including prescriptions of inhaled corticosteroids, smoking cessation counselling, provision of an asthma management plan, demonstration of inhaler technique, and provision of an asthma review)


Shamil Haroon - Chief Investigator - University of Birmingham
Nikita Simms-Williams - Corresponding Applicant - University of Birmingham
Adel Hasan Mansur - Collaborator - University of Birmingham
Krishnarajah Nirantharakumar - Collaborator - University of Birmingham
Prasad Nagakumar - Collaborator - NHS England
Rasiah Thayakaran - Collaborator - University of Birmingham


HES Admitted Patient Care;Patient Level Index of Multiple Deprivation