Asthma drug ratios and exacerbations: claims data from universal health coverage systems

In claims data, controller-to-total asthma drug ratios may reflect adequacy of disease management. We verified whether asthma patients with high ratios (≥ 50%) experienced fewer asthma-related outcomes. Two ratios were studied: that of the inhaled corticosteroids to total asthma drug (ICS/R03) and that of the inhaled corticosteroids plus leukotriene antagonist receptors-to-total asthma drug (ICS+LTRA/R03). Patients aged 13-40 years, with ≥ 3 respiratory drugs dispensed prescriptions in 2005 were selected from the French national claims data. After excluding null ratios, two groups were defined according to ratio values in 2007: low-ratio group (0% < ratio < 50%) and high-ratio group (ratio ≥ 50%). For both ratios, asthma-related outcomes and medical-resource utilisation were compared between groups. Of 2162 patients (mean age 27 years and 52% female), patients with non-null ratios were 81% and 85% for ICS/R03 and ICS+LTRA/R03 ratios, respectively. Patients with high ratios were less likely to receive oral corticosteroids than those in the low-ratio group (relative risk 0.79, 95% CI 0.72-0.88, and 0.80, 95% CI 0.72-0.88, for ICS/R03 and ICS+LTRA/R03, respectively). High ratio groups also presented fewer asthma-related hospitalisations. Significant negative correlations were also observed for both ratios, when studied quantitatively, according to patients' dispensed level of oral corticosteroids in 2007. In claims data, both ICS/R03 and ICS+LTRA/R03 ≥ 50% were related to fewer asthma-related outcomes. Ratios should be explored to identify asthma patients at risk of exacerbations. Low ratios can be considered as risk factors of exacerbation whatever the underlying cause.