Difference in Blood Pressure Readings with Mercury and Automated Devices: Impact on Hypertension Prevalence Estimates in Dar es Salaam, Tanzania

Objectives: (1) To compare blood pressure (BP) readings with an automated arm cuff oscillometric device (AutoBP) to readings with a mercury sphygmomanometer (HgBP) and (2) to evaluate the impact on the prevalence of hypertension (HBP) in a population-based survey. Methods: (1) In a convenience sample ("Comparison Study”), we measured␣BP with both AutoBP (Visomat® OZ2) and␣HgBP and we modeled BP difference (ΔBP=HgBP−AutoBP) with multiple regression analysis. (2) Using ΔBP, we calculated HgBP in a survey previously conducted in Dar es Salaam ("Population Survey”) in which BP was measured with the automatic device Visomat® OZ2 and we compared the prevalence of HBP (≥140/90mmHg or treatment). Results: In the Comparison Study (404 subjects aged 25-64), systolic/diastolic BP was higher by 4.4/4.7mmHg (SE: 0.4/0.3) with HgBP than AutoBP. The prevalence of HBP was 42% with HgBP and 36% with AutoBP (relative difference of 14%). ΔBP was associated with age, BP and arm circumference. In the Population Survey (9.254 subjects aged 25-64), the prevalence of HBP was 17% with calculated HgBP and 14% with AutoBP (relative difference of 20%). Conclusion: A small systematic bias in BP readings between two different devices had large impact on hypertension prevalence estimates. This suggests that automated devices used in epidemiological studies should be validated with particular car

Low utilization of health care services following screening for hypertension in Dar es Salaam (Tanzania): a prospective population-based study

Drug therapy in high-risk individuals has been advocated as an important strategy to reduce cardiovascular disease in low income countries. We determined, in a low-income urban population, the proportion of persons who utilized health services after having been diagnosed as hypertensive and advised to seek health care for further hypertension management. A population-based survey of 9254 persons aged 25-64 years was conducted in Dar es Salaam. Among the 540 persons with high blood pressure (defined here as BP >or= 160/95 mmHg) at the initial contact, 253 (47%) had high BP on a 4th visit 45 days later. Among them, 208 were untreated and advised to attend health care in a health center of their choice for further management of their hypertension. One year later, 161 were seen again and asked about their use of health services during the interval. Among the 161 hypertensive persons advised to seek health care, 34% reported to have attended a formal health care provider during the 12-month interval (63% public facility; 30% private; 7% both). Antihypertensive treatment was taken by 34% at some point of time (suggesting poor uptake of health services) and 3% at the end of the 12-month follow-up (suggesting poor long-term compliance). Health services utilization tended to be associated with older age, previous history of high BP, being overweight and non-smoking, but not with education or wealth. Lack of symptoms and cost of treatment were the reasons reported most often for not attending health care. Low utilization of health services after hypertension screening suggests a small impact of a patient-centered screen-and-treat strategy in this low-income population. These findings emphasize the need to identify and address barriers to health care utilization for non-communicable diseases in this setting and, indirectly, the importance of public health measures for primary prevention of these diseases