Refill rates of accessories for positive airway pressure therapy as a surrogate measure of long-term adherence.

STUDY
OBJECTIVES: To identify and validate a surrogate measure of long-term adherence to positive airway pressure (PAP) therapy in patients with obstructive sleep apnea (OSA).
DESIGN: Retrospective cohort study.
SETTING: Academic center. PARTICIPANTS: 220 consecutive patients with OSA.
INTERVENTIONS: N/A. MEASUREMENTS: In patients with OSA who were receiving PAP therapy (for > 1 year), PAP adherence measured by device-download and defined by Medicare criteria was compared to refill rates for mask and other PAP therapy accessories. First, receiver operating characteristic (ROC) curves were constructed to identify a threshold value of refills per year that discriminated best between PAP adherent and non-adherent patients (derivation set; n = 100). Then the predictive accuracy of the threshold value of refills per year was tested in an additional 120 consecutive patients (validation set).
RESULTS: From the derivation set, ROC curve with good discriminant characteristics (ROC 0.83; 95% confidence intervals [CI], 0.75, 0.91, p < 0.0001) was used to identify a threshold value of refills (0.7 refills/year) for distinguishing PAP adherent and non-adherent patients. Subsequently, when the threshold was applied to the validation set, the likelihood ratio for a positive test (weighted for prevalence) predicting adherence to PAP therapy was 7.3 (95%CI, 3.8, 14), and likelihood ratio for a negative test was 0.6 (95%CI; 0.4, 0.8).
CONCLUSION: Refill rate of PAP accessories exhibited good test characteristics for predicting long-term PAP adherence. Such a surrogate measure based upon insurance claims data can be a powerful epidemiological tool in bioinformatics-aided comparative-effectiveness research and to monitor clinical performance of health systems.