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

Review of investigational medical devices' clinical trials and regulations in Africa as a benchmark for new innovations

Medical technologies present a huge potential in improving global health playing a key role toward achieving Sustainable Development Goal 3 by 2030. A number of clinicians, innovators, business entities and biomedical engineers among others have developed a number of innovative medical devices and technologies to address the healthcare challenges especially in Africa. Globally, medical devices clinical trials present the most acceptable method for determining the risks and benefits of medical device innovations with the aim of ascertaining their effectiveness and safety as compared with established medical practice. However, there are very few medical device clinical trials reported in Africa compared to other regions like USA, UK and Europe. Most of the medical device clinical trials reported in Africa are addressing challenges around HIV/AIDS, maternal health and NCDs. In this mini review, we report about some of the published medical device clinical trials in Africa PubMed and Google Scholar and their associated challenges.

Which cuff should I use? Indirect blood pressure measurement for the diagnosis of hypertension in patients with obesity: a diagnostic accuracy review

OBJECTIVE

To determine the diagnostic accuracy of different methods of blood pressure (BP) measurement compared with reference standards for the diagnosis of hypertension in patients with obesity with a large arm circumference.

DESIGN

Systematic review with meta-analysis with hierarchical summary receiver operating characteristic models. Bland-Altman analyses where individual patient data were available. Methodological quality appraised using Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS2) criteria.

DATA SOURCES

MEDLINE, EMBASE, Cochrane, DARE, Medion and Trip databases were searched.

ELIGIBILITY CRITERIA

Cross-sectional, randomised and cohort studies of diagnostic test accuracy that compared any non-invasive BP tests (upper arm, forearm, wrist, finger) with an appropriate reference standard (invasive BP, correctly fitting upper arm cuff, ambulatory BP monitoring) in primary care were included.

RESULTS

4037 potentially relevant papers were identified. 20 studies involving 26 different comparisons met the inclusion criteria. Individual patient data were available from 4 studies. No studies satisfied all QUADAS2 criteria. Compared with the reference test of invasive BP, a correctly fitting upper arm BP cuff had a sensitivity of 0.87 (0.79 to 0.93) and a specificity of 0.85 (0.64 to 0.95); insufficient evidence was available for other comparisons to invasive BP. Compared with the reference test of a correctly fitting upper arm cuff, BP measurement at the wrist had a sensitivity of 0.92 (0.64 to 0.99) and a specificity of 0.92 (0.85 to 0.87). Measurement with an incorrectly fitting standard cuff had a sensitivity of 0.73 (0.67 to 0.78) and a specificity of 0.76 (0.69 to 0.82). Measurement at the forearm had a sensitivity of 0.84 (0.71 to 0.92) and a specificity 0.75 of (0.66 to 0.83). Bland-Altman analysis of individual patient data from 3 studies comparing wrist and upper arm BP showed a mean difference of 0.46 mm Hg for systolic BP measurement and 2.2 mm Hg for diastolic BP measurement.

CONCLUSIONS

BP measurement with a correctly fitting upper arm cuff is sufficiently sensitive and specific to diagnose hypertension in patients with obesity with a large upper arm circumference. If a correctly fitting upper arm cuff cannot be applied, an incorrectly fitting standard size cuff should not be used and BP measurement at the wrist should be considered.

Comparison of mercury sphygmomanometry blood pressure readings with oscillometric and central blood pressure in predicting target organ damage in youth

OBJECTIVE

Hypertension (HT) is an important risk factor for target organ damage (TOD). New methods for measuring BP are replacing mercury sphygmomanometry in many clinics. We examined the utility of different BP measurement techniques in predicting subclinical TOD in adolescents and young adults.

METHODS

Participants in a study of the cardiovascular effects of obesity and type 2 diabetes were evaluated (N=677, 18±3.3 years, 35% male, 60% non-White, 30% with type 2 diabetes). We measured adiposity, laboratory data, left ventricular mass, carotid intima-media thickness, and pulse wave velocity. BP was measured three times by mercury sphygmomanometry (BPm), using an oscillometric device (BPo), and by arterial tonometry to measure central aortic BP (BPc). Participants were stratified as normotensive, prehypertensive, or hypertensive.

RESULTS

The prevalence of HT in this cohort with a mean BMI of 31 was the highest on BPo measurement (16%), followed by BPm (11%) and BPc (9%; P≤0.001) measurements. BPm was the most consistent in differentiating left ventricular mass and pulse wave velocity among participants in the prehypertensive group as compared with the normotensive and hypertensive groups. Mercury BP measurement was also more sensitive and specific at predicting greater left ventricular mass, pulse wave velocity, and carotid thickness compared with other BP measurement techniques in logistic regression.

CONCLUSION

We conclude that mercury sphygmomanometry should remain the gold standard for evaluation of HT and the risk for TOD in adolescents and young adults.

Comparison between an automated device and a manual mercury sphygmomanometer in an epidemiological survey of hypertension prevalence

BACKGROUND

Automated devices (AD) for measuring blood pressure (BP) are gradually replacing mercury sphygmomanometers (MM) in clinical settings. However, the use of ADs in epidemiological surveys has not been established. We investigated the factors associated with measurement differences when using an MM and an AD.

METHODS

Two trained observers took three BP measurements in 454 subjects as part of an epidemiological survey, alternately using an MM and an AD. BP measurement difference was defined as BPMM - BPAD. Alarm reactions (ARs) were calculated by subtracting the third systolic BP (SBP) measurement from the first SBP.

RESULTS

The mean age of subjects was 50.7±15.4 years (n = 454). The mean BPs using the MM and the AD were 119.8±13.9 vs. 119.5±13.6mm Hg in males and 115.0±16.8 vs. 111.6±15.7mm Hg in females for SBP and 77.7±10.4 vs. 74.7±10.4mm Hg in males and 73.2±9.3 vs. 69.9±10.3mm Hg in females for diastolic BP (DBP). Age, gender, arm circumference, and AR were the factors related to the difference. The concordance correlation coefficients for SBP and DBP were 0.8914 (95% confidence interval [CI], 0.8727-0.9102) and 0.8207 (95% CI, 0.7920-0.8494). The kappa values for the diagnosis of hypertension and Joint National Committee 7 BP classification were 0.6538 (0.5436-0.7641) and 0.5703 (0.5055-0.6351), respectively. The diagnostic sensitivity for hypertension was 59.0%.

CONCLUSIONS

Age, gender, arm circumference, and AR were the factors related to the differences. Despite small differences in the mean values, the agreement and reliability were not good enough to recommend the A&D UA-767PC for adoption in epidemiological surveys of hypertension prevalence.

Blood pressure and levels of Fe, Ca, Mg, Zn, Cu, Na and K in the hair of young Bantu men from Tanzania

Mineral imbalance in the body may significantly contribute to the development and course of hypertension. In this paper, blood pressure figures have been linked to the levels of Fe, Ca, Mg, Zn, Cu, Na and K in hair. The research sample was composed of young men (n = 91) aged 13-21, from the town of Mafinga, Iringa District, Tanzania. The data collected included their age, tribal background and weekly diet. Based on body mass index, the participants were categorised into pre-defined subgroups. To examine how the minerals in question affect blood pressure, correlation analysis and multiple ridge regression analysis were performed. Analysis of ridge regression findings for the researched group (n = 91) shows that the minerals under scrutiny account for systolic blood pressure variation in 13 % and in 15 % for diastolic blood pressure variation. After including two additional variables-calendar age and body mass index-in regression analysis, the ultimate coefficient of determination (R (2)) changes for systolic blood pressure and remains the same for diastolic blood pressure (R (2) = 0.194 and R (2) = 0.156, respectively). Nutritional analysis shows that the students included in the study received insufficient calories per day (1,500-2,200 kcal). The group of students with abnormal blood pressure were not aware of their poor health. Research findings may result from progressive environmental changes and poor nutrition in terms of food quantity and quality, which had an impact on the subjects' blood pressure. Hair analysis used to determine mineral content in the body may be an auxiliary tool in identifying the links between factors leading to the development of hypertension.

Blood pressure monitoring technique impacts hypertension treatment

BACKGROUND

In 2005 the American Heart Association (AHA) released updated recommendations for blood pressure (BP) monitoring in order to ensure accurate BP measurements.

OBJECTIVE

To determine if current methods of BP assessment in an ambulatory clinic result in significantly different BP measurements than those obtained by following the AHA recommendations and if these BP differences impact treatment decisions.

RESEARCH DESIGN

Randomized prospective analysis.

SETTING

University of New Mexico Hospital Adult Internal Medicine clinic.

PATIENTS

Forty adults with hypertension

METHODS

Patient BPs were measured using both the traditional triage method and the AHA-recommended method in cross-over fashion in random order. Two complete medical profile summaries were then constructed for each patient: one for each BP measurement obtained by each technique. These profiles were then reviewed by a panel of providers who provided hypothetical hypertension treatment recommendations.

RESULTS

Individual BP results varied greatly between the two methods. SBP readings differed by ≥5 mmHg in either direction for 68% of patients while 78% of patient's DBP readings differed by ≥2 mmHg in either direction. Overall, 93% of patients had a BP difference of either ≥5 mmHg systolic or ≥2 mmHg diastolic. Five patients were determined to be at goal with the triage method, but were higher than their goal BP with the AHA method Significant differences were also seen in treatment recommendations for a given patient based on the differences seen between the two obtained BP readings. The number of patients with treatment variations between their two profiles ranged from 13% to 23% depending on the reviewing provider (p < 0.01 for all providers).

CONCLUSION

Inaccurate BP assessment is common and may impact hypertension treatment decisions.

Accuracy of oscillometric devices in children and adults

Clinical validation of blood pressure oscillometric devices are almost exclusively conducted in adults. Because oscillometric devices are used in children, it is critical to assess their accuracy also in this population. We compared blood pressure readings using an oscillometric automated device (Dinamap XL, model CR9340) with readings obtained with the mercury auscultatory method in children and adults. Blood pressure was measured in 30 children (15 boys and 15 girls; 9.5+/-1.0 years old) and their parents (25 mothers and 15 fathers; 41.0+/-5.0 years old). In children, mean difference (+/-SD) in systolic blood pressure (DeltaBP) readings (oscillometric-auscultatory) was +0.6+/-4.7 mmHg (range: -10 to +11); mean diastolic DeltaBP was 21.3+/-7.5 mmHg (range: -18 to +19) and decreased with increasing diastolic BP. In adults, mean systolic DeltaBP was +0.4+/-5.2 mmHg (range: -12 to +15) and mean diastolic DeltaBP was -5.2+/-6.0 mmHg (range: -25 to +8) (p<0.001). While the device was not accurate enough to be recommended, our study also shows that the accuracy of blood pressure oscillometric devices can differ between children and adults. Clinical accuracy of oscillometric devices should be tested in the specific populations in whom blood pressure is measured.

Clinical applications of pulse transit time in paediatric critical care

A simple and non-invasive technique, termed pulse transit time (PTT), has shown its potential in long-term investigations such as respiratory sleep studies and cardiovascular studies. Based on these findings, the PTT technique shows relevance for continuous haemodynamic monitoring in critical care. The objective of this review is to understand the potential, applications and limitations of PTT in this clinical setting. Present non-invasive haemodynamic monitoring methods such as automated oscillometric blood pressure (BP) and auscultatory techniques have their known limitations. They tend to underestimate systolic BP while overestimating diastolic BP. Due to the periodic increase in cuff pressure cycles during data acquisition, these techniques may cause much discomfort in elderly geriatric patients, or lessen the cooperation of younger paediatric patients. Thus, there can be adverse effects on therapeutic decisions and possibly clinical outcomes. Documented evidences have indicated that changes observed in PTT are inversely correlated to the corresponding BP changes. In critical care, a simple and accommodating technique like PTT may be useful in providing better comfort for patients during extended monitoring. Being a semi-quantitative measure, blanket recommendations for its utility can then become possible. The basic instrumentations needed are often part of standard critical care monitoring system. Furthermore, PTT also has the potential to monitor the often tachypnoeic respiratory dependent BP changes seen in small infants during critical care.

Prevalence of hypertension in schoolchildren based on repeated measurements and association with overweight

OBJECTIVE

Most studies assess the prevalence of hypertension in pediatric populations based on blood pressure (BP) readings taken on a single visit. We determined the prevalence of hypertension measured on up to three visits in a Swiss pediatric population and examined the association between hypertension and overweight and selected other factors.

METHODS

Anthropometric data and BP were measured in all children of the sixth school grade of the Vaud canton (Switzerland) in 2005-2006. 'Elevated BP' was defined according to sex-specific, age-specific and height-specific US reference data. BP was measured on up to two additional visits in children with elevated BP. 'Hypertension' was defined as 'elevated BP' on all three visits.

RESULTS

Out of 6873 children, 5207 (76%) participated [2621 boys, 2586 girls; mean (SD) age, 12.3 (0.5) years]. The prevalence of elevated BP was 11.4, 3.8 and 2.2% on first, second and thirds visits, respectively; hence 2.2% had hypertension. Among hypertensive children, 81% had isolated systolic hypertension. Hypertension was associated with excess body weight, elevated heart rate and parents' history of hypertension. Of the children, 16.1% of boys and 12.4% of girls were overweight or obese (CDC criteria, body mass index >or= 85th percentile). Thirty-seven percent of cases of hypertension could be attributed to overweight or obesity.

CONCLUSIONS

The proportion of children with elevated BP based on one visit was five times higher than based on three measurements taken at few-week intervals. Our data re-emphasize the need for prevention and control of overweight in children to curb the global hypertension burden.