Real-world Effectiveness of Combination Therapies in Primary Care Asthma Management

Exacerbation control (a composite proxy measure)

Controlled: Absence of: (i) Asthma-related: 1. Hospital attendance or admission 2. A\&E attendance, OR 3. Out of hours consultations, OR 4. Out-patient department attendance (ii) GP consultations for lower respiratory tract infection (iii) Prescriptions for acute courses of oral steroids

Time frame: One-year outcome period

Treatment success 1

(i) Exacerbation control AND (ii) No change in therapeutic regimen: * ≥50% increase in ICS dose relative to IPD dose, and/or * Change in ICS/LABA drug within class, and/or * Change in delivery device, and/or * Use of additional (defined as not received during baseline year) therapy as defined by: theophylline, leukotriene receptor antagonists (LTRAs).

Time frame: One-year outcome period

Asthma hospitalisations

1. Definite: Hospitalisations coded with an asthma read code 2. Definite + Probable: Hospitalisations with an asthma read code + uncoded hospitalisations occurring within a 7-day window (either side of the hospitalisation date) of an asthma read code

Time frame: One-year outcome period

Compliance with ICS/LABA therapy

Compliance calculation based on prescription refills and (where possible) compliance questionnaire data

Time frame: One-year outcome period

Use of reliever medication

average daily dosage during outcome year. Outcome SABA usage will be categorised within ranges used to match baseline SABA use to optimise matching of the treatment arms.