Physician assessments of medication adherence and decisions to intensify medications for patients with uncontrolled blood pressure: still no better than a coin toss

Abstract

Background: Many patients have uncontrolled blood pressure (BP) because they are not taking medications as prescribed. Providers may have difficulty accurately assessing adherence. Providers need to assess medication adherence to decide whether to address uncontrolled BP by improving adherence to the current prescribed regimen or by intensifying the BP treatment regimen by increasing doses or adding more medications.

Methods: We examined how provider assessments of adherence with antihypertensive medications compared with refill records, and how providers' assessments were associated with decisions to intensify medications for uncontrolled BP. We studied a cross-sectional cohort of 1169 veterans with diabetes presenting with BP ≥140/90 to 92 primary care providers at 9 Veterans Affairs (VA) facilities from February 2005 to March 2006. Using VA pharmacy records, we utilized a continuous multiple-interval measure of medication gaps (CMG) to assess the proportion of time in prior year that patient did not possess the prescribed medications; CMG ≥20% is considered clinically significant non-adherence. Providers answered post-visit Likert-scale questions regarding their assessment of patient adherence to BP medications. The BP regimen was considered intensified if medication was added or increased without stopping or decreasing another medication.

Results: 1064 patients were receiving antihypertensive medication regularly from the VA; the mean CMG was 11.3%. Adherence assessments by providers correlated poorly with refill history. 211 (20%) patients did not have BP medication available for ≥ 20% of days; providers characterized 79 (37%) of these 211 patients as having significant non-adherence, and intensified medications for 97 (46%). Providers intensified BP medications for 451 (42%) patients, similarly whether assessed by provider as having significant non-adherence (44%) or not (43%).

Conclusions: Providers recognized non-adherence for less than half of patients whose pharmacy records indicated significant refill gaps, and often intensified BP medications even when suspected serious non-adherence. Making an objective measure of adherence such as the CMG available during visits may help providers recognize non-adherence to inform prescribing decisions.

Figure 1

Study flow diagram.

Figure 2

Provider Assessment of Adherence(Histogram).

Figure 3

Comparing Identification of Significant Non-adherence by Provider Assessment and Refill History (CMG= Continuous Multiple-interval Gap measure).

Figure 4

Comparing Identification of Significant Non-adherence by Provider Assessment and Refill History (CMG= Continuous Multiple-interval Gap measure).Area A (circle outlined with solid border): 258 (24%) patients identified by provider as having significant non-adherence. Area B (circle outlined by dashed border): 211 (20%) patients identified by refill measure (CMG ≥20%) as having significant non-adherence. Area C (overlap of areas A and B): 79 (7%) patients identified as having significant non-adherence by both the provider assessment and refill measure (CMG). Area D (surrounding gray box): 674 patients without evidence of non-adherence by either provider assessment or refill measure (CMG), including 22 patients for whom the providers did not provide an adherence assessment by either post-visit question.

Figure 5

Example of Calculation of Refill Adherence Measure.