Implementation of the National Asthma Guidelines in New Zealand: a retrospective patient-level study of the change to anti-inflammatory reliever therapy in 324,972 patients

Why clinicians should know about it

• Picked for Family Practice (paper of the day, 1 November 2026): Large real-world evaluation of guideline-recommended asthma inhaler changes

Abstract

BACKGROUND: The updated New Zealand asthma guidelines in 2020, aligning with global asthma guideline recommendations, advocated for a fundamental shift from short-acting β2-agonist (SABA) reliever therapy to anti-inflammatory reliever (AIR) therapy (ICS-formoterol) in adults and adolescents. While aggregate population-level data indicate increased ICS-formoterol dispensings, patient-level changes in medication use remain unclear. We examined medication use patterns to assess early practice changes across the entire asthma population. METHODS: We conducted a retrospective study using the New Zealand national linked health datasets. Patients aged ≥12 with asthma were identified from hospitalisation and/or dispensing data, and categorised by the complete set of inhaler classes dispensed in the three months preceding their final dispensing date within the baseline (July 2018-June 2020) and post-guideline (June 2020-June 2022) periods. Nine mutually exclusive categories were defined without applying any hierarchy between medications: SABA only; ICS, non-formoterol ICS-LABA, and ICS-formoterol, each with and without a concurrently dispensed SABA; other regimens; and no inhaled medication. Age subgroups (12-44 and ≥ 45 years) were examined. Children aged < 12 years throughout follow-up, who were outside the scope of the recommendation, served as a comparison cohort for difference-in-differences estimation. FINDINGS: The cohort included 324,972 patients aged ≥12 years. At baseline, the SABA-only group was the most common (30.5%). Post-guideline, dispensing of the guideline-recommended regimen, ICS-formoterol without SABA, more than doubled from 10.9% to 23.8%, and any ICS-formoterol use rose from 18.9% to 34.5%. The proportion of patients dispensed any SABA fell from 74.1% to 60.8%. Of patients dispensed SABA only pre-guideline, 57.1% were dispensed SABA only again, while 17.6% changed to ICS-formoterol without SABA and 8.1% to ICS-formoterol with SABA. Continuity was high among patients on maintenance therapy (55.9% for ICS, 74.3% for non-formoterol ICS-LABA) and among those already dispensed ICS-formoterol (89.0%). Among post-guideline ICS-formoterol users, 31.1% were also dispensed a SABA, compared with 63.8% of non-formoterol ICS-LABA users and 70.2% of ICS users. Using children aged < 12 years as a comparison cohort, difference-in-differences estimates were +8.4 percentage points for ICS-formoterol without SABA and -8.3 percentage points for total SABA supply, but -0.2 percentage points for SABA monotherapy. INTERPRETATION: The impact of the guideline change was substantial but selective. While the update facilitated transition for patients already receiving maintenance therapy, most patients on SABA-only regimens did not switch to the preferred AIR regimen. Further targeted implementation strategies beyond guideline publication are required to address this gap and ensure evidence-based care is consistently delivered. FUNDING: None.

Abstract as published, via PubMed.