Performance of database-derived severe exacerbations and asthma control measures in asthma: responsiveness and predictive utility in a UK primary care database with linked questionnaire data.

Background: Observational research is essential to evaluate the real-life effectiveness of asthma treatments and can now make use of outcomes derived from electronic medical records.

Aim: The aim of this study was to investigate the utility of several database outcome measures in asthma.

Methods: This study identified cohorts of patients with active asthma from a UK primary care database - Optimum Patient Care Research Database - approximately 10% of which was prospectively supplemented with questionnaire data. The "Questionnaire cohort" included patients aged 18-60 years with valid questionnaire data and 1 year of continuous primary care data. Separate "ICS initiation" and "ICS step-up" cohorts included patients aged 5-60 years initiated on inhaled corticosteroids (ICSs), who had 1 year of continuous primary care data before, and after, this index visit. Database measures of asthma symptom control and exacerbations were identified in the Optimum Patient Care Research Database and cross-tabulated with corresponding patient-reported (questionnaire) data. Responsiveness of the database outcomes was analyzed, using McNemar's and Wilcoxon's signed rank tests, and Poisson regression was used to estimate the association between database outcomes and future risk of database exacerbations, in the ICS initiation cohort.

Results: The final study included 2,366 Questionnaire cohort patients and 51,404 ICS initiation patients. Agreement between patient-reported and database-recorded exacerbations was fair (kappa 0.35). Following the initiation of ICS, database risk domain asthma control (based on exacerbations) improved (proportion of patients with uncontrolled asthma decreased from 24.9% to 18.6%; P<0.001) and mean number of database exacerbations decreased from 0.09 to 0.08 per patient per year (P=0.001). However, another measure of asthma control which includes short-acting beta-agonist prescription as part of the definition did not show this improvement. Patients with prior exacerbations had a higher risk of future exacerbation (rate ratio [95% confidence interval], 3.23 [3.03-3.57]).

Conclusion: Asthma control and exacerbations derived from primary care databases were responsive, with the exception of short-acting beta-agonist prescriptions, and useful for risk prediction.