Validity of Self-reported Blood Pressure Control in People with Hypertension Attending a Primary Care Center

Objectives: The aim of this study was to estimate the validity of self-reported blood pressure control and medication use in people with hypertension, with and without diabetes.

Methods: In a sample of 161 patients with hypertension in a family health team in Ontario, we applied questions from the 2009 Survey on Living with Chronic Disease in Canada Hypertension Component and compared responses against objectively measured and chart-abstracted clinical indicators. Objective blood pressure control was defined as a blood pressure of less than 130/80 mmHg and less than 140/90 mmHg for individuals with and without diabetes, respectively.

Results: Self-reported blood pressure control showed reasonable sensitivity (83±11 and 78±10%) but low specificity (30±19 and 58±21%) in people with and those without diabetes, respectively. In the subgroup with diabetes, specificity improved to 88±11% when blood pressure control was defined on the basis of a 140/90 mmHg target. Self-reported and chart-abstracted numbers of prescribed antihypertensive medications showed fair agreement (κ=0.7); 9 and 14% of patients overestimated and underestimated the number of prescribed medications, respectively.

Conclusion: Although most individuals with controlled hypertension reported having controlled blood pressure, a large proportion of individuals with uncontrolled hypertension also reported that their blood pressure was controlled. This level of misclassification suggests that in a family medicine clinic population and in health survey contexts, a self-reported measure of blood pressure control may not be useful for assessing hypertension control.