Predicting blood pressure outcomes using single-item physician-administered measures: a retrospective pooled analysis of observational studies in Belgium.

Background: Patient adherence is often not monitored because existing methods of evaluating adherence are either burdensome or do not accurately predict treatment outcomes.
Aim: To examine whether two simple, single-item physician-administered measures of patient adherence to antihypertensive medication are predictive of blood pressure outcomes.
Design and Setting: Retrospective database analysis of patients with hypertension treated in Belgian primary care.
Method: Using pooled data from five observational studies, a sample was identified of 9725 patients who were assessed using two single-item physician-administered measures of adherence to antihypertensive medication: the first item of the Basel Assessment of Adherence Scale (BAAS) and the Visual Analogue Scale (VAS). These two assessment tools were administered by GPs during regular appointments with patients. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and combined SBP/DBP were measured at baseline and at 90 days.
Results: BAAS-identified adherent patients achieved lower mean SBP and DBP compared with non-adherent patients at 90 days (P<0.001), and had odds ratios of achieving blood pressure control of 0.66 (95% confidence intervals (CI) = 0.61 to 0.73, P<0.001) for SBP, 0.69 (95% CI = 0.62 to 0.76, P<0.001) for DBP, and 0.65 (95% CI = 0.59 to 0.72, P<0.001) for combined SBP/DBP. For VAS-identified adherent patients, the odds ratios of achieving blood pressure control were 0.93 (95% CI = 0.86 to 1.00, P<0.001) for SBP, 0.79 (95% CI = 0.73 to 0.85, P<0.001) for DBP, and 0.91 (95% CI = 0.84 to 0.99, P<0.001) for combined SBP/DBP.
Conclusions: The first item of the BAAS and the VAS are independent predictors of blood pressure control. These methods can be integrated seamlessly into routine clinical practice by allowing GPs to quickly evaluate a patient's adherence and tailor treatment recommendations accordingly.
(© British Journal of General Practice 2015.)