Concurrent and Predictive Validity of a Self-reported Measure of Medication Adherence

TLDR

Adherence to medical regimens remains a major clinical problem in essential hypertension and other drug‑treated conditions. The article evaluates the psychometric properties and concurrent and predictive validity of a four‑item self‑reported adherence measure that can be integrated into routine visits. The scale’s items target medication‑taking barriers and enable reinforcement of adherence, while adherence was assessed after an 18‑month education program and blood pressure monitored over 3 years. The scale demonstrated concurrent validity at 2 years and predictive validity at 5 years, with 75 % of high‑scoring patients achieving adequate blood pressure control at year 5 versus 47 % of low‑scoring patients (P < 0.01).

Abstract

Adherence to the medical regimen continues to rank as a major clinical problem in the management of patients with essential hypertension, as in other conditions treated with drugs and life-style modification. This article reviews the psychometric properties and tests the concurrent and predictive validity of a structured four-item self-reported adherence measure (alpha reliability = 0.61), which can be easily integrated into the medical visit. Items in the scale address barriers to medication-taking and permit the health care provider to reinforce positive adherence behaviors. Data on patient adherence to the medical regimen were collected at the end of a formalized 18-month educational program. Blood pressure measurements were recorded throughout a 3-year follow-up period. Results showed the scale to demonstrate both concurrent and predictive validity with regard to blood pressure control at 2 years and 5 years, respectively. Seventy-five percent of the patients who scored high on the four-item scale at year 2 had their blood pressure under adequate control at year 5, compared with 47% under control at year 5 for those patients scoring low (P less than 0.01).