Purpose: "Controllers-to-total asthma drug" ratios computed from claims data identify asthmatics at risk of exacerbations. Direct link of ratios to data obtained from patients, such as control and recent outcomes, would facilitate their interpretation. We studied the relationship between R1 ratio (inhaled corticosteroids (ICS)/total anti-asthma drug ratio) and the Asthma Control Test. Comparisons were also conducted for secondary outcomes (asthma-related hospital contacts, monthly medical contacts, use of oral corticosteroids, and perception of disease burden). Results with R1 ratio were compared with those obtained with a second ratio, "ICS-plus-leukotriene receptor antagonist/total asthma drug" (R2 = ICS + leukotriene receptor antagonist/total anti-asthma drugs).
Methods: A survey was conducted in community pharmacies. Patients visiting with a prescription of anti-asthma drug and ≥12 months of drug dispensing recorded in the pharmacy were consecutively recruited. Dispensing data were linked to patient-reported outcomes. Asthma control and secondary outcomes were compared for both ratios between low-controller-ratio (R < 50%) and high-controller-ratio groups (R ≥ 50%), after excluding null values.
Results: Of the 919 eligible patients (mean age 37 years, 55% women), 90.2% and 92.4% had non-null values for R1 and R2, respectively. Compared with the low-controller-ratio groups, adjusted risks of being uncontrolled were significantly lower in the high-controller-ratio groups (RR = 0.64, 95%CI [0.54, 0.77] and RR = 0.57, 95%CI [0.47, 0.70], for R1 and R2 ratios, respectively). Likewise, fewer patients with secondary outcomes were observed in the high-controller-ratio groups, for both ratios.
Conclusion: Asthma was better controlled among patients with high controller ratios, along with fewer asthma-related outcomes, for both R1 and R2 ratios. This confirms the utility of asthma/drug ratios in identifying patients at risk of exacerbations, notably in claims data.
Keywords: asthma therapy; community pharmacy; control; exacerbations; inhaled corticosteroids; pharmacoepidemiology.
Copyright © 2014 John Wiley & Sons, Ltd.