An analysis of blood pressure measurement in a primary care hospital in Swaziland

BACKGROUND: Measurement of blood pressure (BP) is done poorly because of both human and machine errors. AIM: To assess the difference between BP recorded in a pragmatic way and that recorded using standard guidelines; to assess differences between wrist- and mercury sphygmomanometer-based readings; and to assess the impact on clinical decision-making. SETTING: Royal Swaziland Sugar Corporation Mhlume hospital, Swaziland. METHOD: After obtaining consent, BP was measured in a pragmatic way by a nurse practitioner who made treatment decisions. Thereafter, patients had their BP re-assessed using standard guidelines by mercury (gold standard) and wrist sphygmomanometer. RESULTS: The prevalence of hypertension was 25%. The mean systolic BP was 143 mmHg (pragmatic) and 133 mmHg (standard) using a mercury sphygmomanometer; and 140 mmHg for standard BP assessed using wrist device. The mean diastolic BP was 90 mmHg, 87 mmHg and 91 mmHg for pragmatic, standard mercury and wrist, respectively. Bland Altman analyses showed that pragmatic and standard BP measurements were different and could not be interchanged clinically. Treatment decisions between those based on pragmatic BP and standard BP agreed in 83.3% of cases, whilst 16.7% of participants had their treatment outcomes misclassified. A total of 19.5% of patients were started erroneously on anti-hypertensive therapy based on pragmatic BP. CONCLUSION: Clinicians need to revert to basic good clinical practice and measure BP more accurately in order to avoid unnecessary additional costs and morbidity associated with incorrect treatment resulting from disease misclassification. Contrary to existing research, wrist devices need to be used with caution.