Pragmatic versus standardised BP measurement : an analysis of BP measurement in a primary care hospital in Swaziland
Thesis (MMed)--Stellenbosch University, 2013.
ENGLISH SUMMARY : Background: Measurement of blood pressure (BP) is done poorly due to both human and instrument errors. The standard protocol for measurement is often not followed by healthcare workers. Objectives: There were three main objectives: firstly to assess the difference between BP recorded in a pragmatic way and that recorded using standard BP measurement guidelines; secondly to assess difference between BP measurements done by wrist sphygmomanometer compared to mercury sphygmomanometer; and finally to assess if the differences affect decision to start or adjust hypertension treatment. Setting: RSSC Mhlume hospital, Swaziland Study design: cross sectional study Study Method: Following consent, BP was assessed in a pragmatic way by nurse practitioner who made treatment decisions. Thereafter, patients had BP re-assessed using standard BP protocol by mercury (gold standard) and wrist sphygmomanometer. In addition demographic and clinical data was collected. Results: The prevalence of hypertension was 25%. The mean systolic BP was 143 mmHg for pragmatic BP, 133 mmHg for standard BP using 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. Pearson and intra-class correlation coefficients were similar for both systolic and diastolic BP and for all BP measurement pairs which were being compared. Bland Altman analyses showed that pragmatic and standard BP measurement were different and could not be used interchangeably. Standard mercury and wrist based methods were not clinically interchangeable. Treatment decisions between those based on pragmatic BP and standard BP agreed in 83.3% of cases; 16.7% of participants had their treatment outcomes misclassified. Twenty-five percent of patients were erroneously started on anti-hypertensive therapy based on pragmatic BP. Conclusion: There is a difference between pragmatic and standard BP measurements which affect decisions not to start treatment and decision to start treatment but not treatment alteration decision for those already on treatment. There are also marked differences between wrist and standard mercury based BP devices. Clinicians need to revert to basic good practice and measure BP more accurately to avoid unnecessary additional costs and morbidity associated with incorrect treatment due to disease misclassification. Contrary to existing research, wrist devices need to be used with caution.
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