Understanding the relationship among pharmacoadherence measures, asthma control test scores, and office-based spirometry

Abstract

BackgroundThis study used accepted asthma metrics and pharmaceutical claim data to develop a new asthma metric as a possible surrogate for spirometry and to better assess asthma control. ObjectiveTo develop and validate a new asthma metric called the Rescue Index (RI) based on β2-agonist dispensings and to test the feasibility of a multivariate model to construct a global asthma metric called the Asthma Control Index (ACI). MethodsThis prospective, observational, multicenter cohort study was conducted at the Naval Medical Center San Diego (NMCSD) and at the Phoenix VA Health Care System (PVAHCS). Pharmacy claim data were correlated with the ACT, Medication Adherence Report Scale for Asthma (MARS-A), and spirometry using univariate and multivariate analyses. ResultsA total of 263 individuals enrolled in the study, and 95 (PVAHCS) and 156 (NMCSD) individuals completed the study. In the PVAHCS, the ACT correlated with the asthma medication ratio (AMR) (ρ = 0.37, P < .001) and inversely correlated with the RI (ρ = −0.33, P = .001), the RI inversely correlated with forced expiratory volume in 1 second (FEV1) (ρ = −0.22, P = .03) and the FEV1 to forced vital capacity ratio (ρ = 0.22, P = .03). In the NMCSD population, the ACT correlated with the MARS-A (ρ = 0.23, P = .006), FEV1 did not correlate with ACT (ρ = 0.09, P = .25) or MARS-A (ρ = 0.16, P = .047) but directly correlated with the RI (ρ = 0.19, P = .03). The AMR was strongly inversely correlated with RI in both populations (−0.74, P < .001 in the PVAHCS group and −0.78, P < .001 in the NMCSD group). When multivariate models were applied to the NMCSD and PVAHCS groups, the combination of RI and MARS-A was the best predictor of spirometry. ConclusionThe RI shows promise as a new asthma metric because it correlated with AMR in both cohorts. However, because RI correlated with adult spirometry and ACT only, further validation studies are needed before RI may be included in an ACI metric.