Is higher population-level use of ICS/LABA combination associated with better asthma outcomes? Cross-sectional surveys of nationally representative populations in New Zealand and Australia

Abstract

Background and objective: New Zealand (NZ) and Australia (AU) have similarly high asthma prevalence; both have universal public health systems, but different criteria for subsidized medicines. We explored differences in asthma management and asthma-related outcomes between these countries.

Methods: A web-based survey was administered in AU (2012) and NZ (2013) to individuals aged ≥16 years with current asthma, drawn randomly from web-based panels, stratified by national population proportions. Symptom control was assessed with the Asthma Control Test (ACT). Healthcare utilization was assessed from reported urgent doctor/hospital visits in the previous year.

Results: NZ (n = 537) and Australian (n = 2686) participants had similar age and gender distribution. More NZ than Australian participants used inhaled corticosteroid (ICS)-containing medication (68.8% vs 60.9%; P = 0.006) but ICS/long-acting β₂ -agonist (LABA) constituted 44.4% of NZ and 81.5% of Australian total ICS use (P < 0.0001). Adherence was higher with ICS/LABA than ICS-alone (P < 0.0001), and higher in NZ than in AU (P < 0.0001). ACT scores were similar (P = 0.41), with symptoms well controlled in 58.6% and 54.4% participants, respectively. More NZ participants reported non-urgent asthma reviews (56.6% vs 50.4%; P = 0.009). Similar proportions had urgent asthma visits (27.9% and 28.6%, respectively, P = 0.75).

Conclusion: This comparison, which included the first nationally representative data for asthma control in NZ, showed that poorly controlled asthma is common in both NZ and AU, despite subsidized ICS-containing medications. The greater use of ICS-alone in NZ relative to ICS/LABA does not appear to have compromised population-level asthma outcomes, perhaps due to better adherence in NZ. Different ICS/LABA subsidy criteria and different patient copayments may also have contributed to these findings.

Keywords: antiasthmatic agents/therapeutic use; asthma; asthma/epidemiology; asthma/therapy; cross-sectional studies.