Abstract P026: Relationship Between Antihypertensive Adherence and Emergency Department Blood Pressure

Abstract

Background: Blood pressure is often uncontrolled in the Emergency Department (ED), but the contribution of medication non-adherence to this is not known. Methods: Three hundred ED patients with hypertension were enrolled from June 2012 to April 2013 to evaluate the association of antihypertensive adherence (measured by serum assay and by survey) with systolic blood pressure (SBP) in the ED. Presence of anti-hypertensive medications in the blood was detected using a previously validated mass spectrometric assay. Adherence was defined as the ratio of detected to prescribed antihypertensive medications (1=completely adherent, 0=completely non-adherent, <1=partially non-adherent). Patients also completed the Adherence to Refills and Medications Scale (ARMS, where a score of 12 defines adherence and >12 indicates some degree of non-adherence). Spearman’s rho was used to evaluate correlation of the assay and ARMS. A single BP was measured by research staff using an oscillometric cuff with the patient in a seated position. Multiple linear regression was used to assess the relationship between adherence and SBP, adjusting for age, sex, race, insurance, literacy/numeracy, education, and comorbid conditions. Missing numeracy for 18 subjects was imputed. Results: Three participants failed to meet inclusion criteria. Remaining 297 patients were 59.1±11.2 (SD) years old, 53.9% female, 62.3% White, 37.7% diabetic, and 24.6% had chronic kidney disease. Patients were prescribed a median of 2 medications (interquartile range 1 to 3, maximum 5). Mean SBP was 136.7±24.2 mmHg. By the assay, 214 (72.1%) patients were adherent, 59 (19.9%) partially non-adherent, and 24 (8.0%) completely non-adherent. By ARMS, 65 (21.9%) were adherent, 232 (78.1%) were non-adherent (rho=-0.23, p<0.001). Adherence by assay was associated with 11.6mmHg lower SBP (95% CI -17.7 to -5.4 mmHg, p<0.001) compared to partial or complete non-adherence. Adherence (by ARMS) was associated with 5.9 mmHg lower SBP, but this was not statistically significant (95% CI -12.6 to 0.8 mmHg, p=0.08). Conclusions: In this preliminary study, antihypertensive adherence measured by a mass spectrometry assay was associated with lower SBP among patients in the ED. The assay may be a useful tool for future research.