Comparison of two methods of measuring adherence to inhalers, in terms of their association with control symptoms in the asthma patient

Objective: To determine the association between the degree of symptom control in the adult asthmatic patient and adherence to maintenance inhaled therapy, measured by two different methods. Methodology: Cross-sectional study, which included the first 183 consecutive asthmatic patients attended for any medical reason by a panel of recruiting physicians from three autonomous communities in northern Spain (Asturias, Cantabria and the Basque Country). Adherence to inhalers was determined by means of the Test of Adherence to Inhalers (TAI) and through the electronic prescription refill rate (EPRR), calculating the % of drug dispensed with respect to that prescribed, for a retrospective period of 12 months. Clinic control was determined using the Asthma Control Test (ACT). Results: A statistically significant correlation was observed between TAI and ACT (the higher the TAI scores, the higher the ACT scores): Spearman's rho coefficient=0.23; p=0.002. 38.8% (n=71) presented an uncontrolled asthma (ACT<20 points). Patients with poor adherence according to TAI (≤45 points TAI 10-items) had 2.20 fold increased risk of having uncontrolled asthma (ACT<20): Odds Ratio (OR)=2.20; 95% confidence interval (95%CI) (1.20-4.04). This association was maintained when adjusting for age, sex and asthma severity (mild persistent vs moderate persistent): Adjusted OR=2.47; 95%CI (1.27-4.79). Regarding the EPRR, we obtained a correlation close to null and not significant (rho= -0.02; p=0.789) without finding significant associations in the form of ORs either. Conclusions: Among the two methods of measuring adherence, TAI was the only one that correlated statistically significantly with ACT and was independently associated with poor disease control.