Abstract
After starting antihypertensives, blood pressure is monitored for several reasons, including assessment of adherence. We aimed to estimate the accuracy of blood pressure monitoring for detecting early nonadherence. We conducted a secondary analysis of the Perindopril Protection Against Recurrent Stroke Study (PROGRESS), a large randomized trial of blood pressure lowering to reduce the risk of recurrent stroke. We compared change in blood pressure 3 months after randomization in people who had discontinued treatment (nonadherent) with those who stayed on treatment (adherent). We also used an indirect method, assessing whether change in blood pressure discriminated between active (adherent) and placebo (nonadherent) groups. Both methods gave similar results. For the 3433 subjects, the mean (SD) of the change in systolic blood pressure was -15.8 mm Hg (SD 18.7 mm Hg) in the adherent group and -4.2 mm Hg (SD 18.1 mm Hg) in the nonadherent group. After recalibration of the mean change in the nonadherent group to 0 mm Hg and in the adherent group to -11.6 mm Hg, the absence of a fall in systolic blood pressure at 3 months had a sensitivity of 50% and a specificity of 80% for detecting nonadherence (50% of nonadherent patients and 20% of adherent patients had a rise in blood pressure). Discriminatory power was modest over the range of cutoffs (area under the receiver-operator curve 0.67). Monitoring blood pressure is poor at detecting nonadherence to blood pressure-lowering treatment. Further research should look at other methods of assessing adherence.
Highlights
After starting antihypertensives, blood pressure is monitored for several reasons, including assessment of adherence
Nonadherence is thought to be an important reason why the full anticipated effect of therapies is not achieved in the community,[8] with adherence rates often substantially lower than those achieved in trial populations
Estimates of adherence in the community vary from 50% to 70%8 compared with adherence rates of Ͼ80% in many trial populations.[9]
Summary
Blood pressure is monitored for several reasons, including assessment of adherence. After starting a patient on blood pressure–lowering treatment, usual clinical practice is to regularly monitor blood pressure. Recent reports question the value of current monitoring strategies for assessing the patient’s initial[1,2] and longer-term response to treatment[3] because of the substantial usual background variability in an individual’s blood pressure levels. Estimates of adherence in the community vary from 50% to 70%8 compared with adherence rates of Ͼ80% in many trial populations.[9] Early discontinuation in particular appears to be a major problem, with a recent study reporting that 30% of patients prescribed long-term blood pressure–lowering medication discontinued within the first 100 days, 36% by 6 months, and 50% by 1 year.[10] The lower levels of adherence in community populations are attributed primarily to inadequate communication between physicians and their patients, side effects and out-of-pocket cost may contribute.[11]. Therapy, measurement of blood drug levels, patient questionnaires, pill counts, prescription refill rates, electronic medication monitoring, and measurement of physiological markers such as blood pressure.[13]
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