Cross-cultural validation of the hill-bone compliance to high blood pressure therapy scale in a South African, primary healthcare setting

Objectives: Hypertension is prevalent, underdiagnosed, and inadequately treated in Black South Africans. However, few studies have addressed barriers to hypertension care and control in this community. The aim of this study was to validate the Hill-Bone Compliance to High Blood Pressure Therapy Scale (HB Comp Scale) for use in a South African primary healthcare setting. This instrument consists of three subscales, medications-compliance, appointment making, and salt intake. Methods: A demographic questionnaire and the HB scale were translated into the first language of the subjects and then back-translated into English. Hypertensive patients (N=98) were recruited from primary healthcare clinics in Cape Town. Blood pressure was measured with an Omron electronic blood pressure manometer, after 5 min of seated rest. Item-analysis was conducted to determine internal consistency of the HB Comp Scale; Spearman rank order correlations were used to assess the relationship between compliance scores and blood pressure. Results: A modified scale consisting of only 10 items demonstrated reasonable internal consistency (item-total correlations all >.31, and a standardized Cronbach α of 0.79), with an average interitem correlation of .26. In addition, the modified scale had significant predictive validity in that noncompliance predicted higher diastolic blood pressures (p=.21, P<.05) and medication noncompliance tended to predict higher systolic blood pressures (p=.20, P<.06). Appointment-making and dietary salt-intake subscales were not internally consistent. Conclusions: We demonstrated criterion validity and internal consistency for a modified Hill-Bone Compliance Scale, in Black, urban, hypertensive, South African patients. Results compare favorably with those from an urban African-American setting (standardized Cronbach α was .74-.84).