Is It Accurate to Visually Read a Blood Pressure Reading

J Clin Diagn Res. 2016 Mar; 10(3): LC11–LC14.

Which is More than Accurate in Measuring the Claret Force per unit area? A Digital or an Aneroid Sphygmomanometer

Bhaskar Shahbabu

¹ Junior Resident, Department of PSM, AIIH&PH, Kolkata, Due west Bengal, India.

Aparajita Dasgupta

² Professor and HOD, Department of PSM, AIIH&PH, Kolkata, West Bengal, India.

Kaushik Sarkar

³ Junior Resident, Department of PSM, AIIH&PH, Kolkata, W Bengal, Republic of india.

Sanjaya Kumar Sahoo

⁴ Junior Resident, Department of PSM, AIIH&PH, Kolkata, West Bengal, India.

Received 2015 May 31; Revisions requested 2015 Aug 17; Accustomed 2015 Dec 11.

Abstract

Introduction

Hypertension is one of the major public wellness trouble affecting the whole earth so its authentic measurement is of utmost importance for its early on diagnosis and management. Concerns related to the potential ill effects of mercury on health and surround, has led to the widespread use of non-mercury sphygmomanometers.

Aim

A report was conducted to compare the accuracy of readings of aneroid and digital sphygmomanometers in reference to mercury sphygmomanometers and determine the hypertensive nomenclature agreement between the mercury and not-mercury devices.

Materials and Methods

The study was conducted in an OPD of a health heart in a rural community of West Bengal which is the rural field practice expanse of our constitute. An aneroid and a digital sphygmomanometer were compared to a properly calibrated mercury sphygmomanometer. All the subjects above the historic period of 25 years, in two days per week, selected randomly from 5 working days per calendar week in a flow of one calendar month were selected. Two blood force per unit area readings of each of 218 study subjects was recorded with each pretested sphygmomanometer. Paired t-exam, Kappa coefficients, sensitivity and specificity tests were done. Receiver Operating Characteristics bend analysis was done and Youden index was estimated to detect the optimal cut off point for the diagnosis of hypertension by non-mercury sphygmomanometers.

Results

Data analysis of 218 study subjects showed the hateful deviation of the mercury reading and the test device was much less for aneroid than that of the digital device for both systolic and diastolic blood pressure level. More than 89% of aneroid readings and less than 44% of the readings by digital device had absolute departure of 5mm Hg. when compared with the mercury readings for both systolic and diastolic blood force per unit area. Sensitivity and specificity of aneroid device was higher (86.7% and 98.7%) than digital device (lxxx% and 67.7%). Receiver Operating Feature curve had larger expanse nether the bend for aneroid device than digital device for both SBP and DBP.

Conclusion

The aneroid device had ameliorate accurateness than the digital device equally compared to mercury sphygmomanometer and should exist used for proper and better direction.

Keywords: Blood pressure level measurement, Digital sphygmomanometer, Hypertension, Receiver operating characteristics curve, youden index

Introduction

Increment in blood force per unit area is a grave hazard factor because the population health. It not only increases the risk of coronary middle disease and ischaemic and haemorrhagic stroke, but is also associated with numerous complications like heart failure, peripheral vascular illness, renal impairment, retinal haemorrhage and visual damage. Moreover, literatures advise that interventions targeted to reduce the blood pressure level beneath the level of 140/ninety mm of Hg reduce such adventure substantially [1]. In recent years, there has been a abrupt rise in the magnitude of the problem of hypertension across the globe. Globally 7.5 million deaths are attributable to hypertension which constitutes about 12.8 % of all deaths, which in turn accounts for more than than fifty meg disability adapted life years (DALYS) or three.seven% of total DALYS [one]. Regarding the brunt of the disease, the overall prevalence among adults aged 25 years or above was around 40% globally, while in India information technology was more one fifth of the total population of that age group [2].

It has been estimated that a rise in systolic BP by only 5 mm of Hg would outcome in approximately 25% increase in the chances of fatal stroke and fatal myocardial infarction [iii]. While such findings substantiate the catastrophic consequences of underestimating blood pressure in an individual, information technology has been estimated that overestimation of truthful blood pressure by same level would result in inappropriate treatment with anti-hypertension medications in nigh 30 million Americans. They would likewise be exposed to adverse drug effects, psychological effects of misdiagnosis, and unnecessary toll [4]. Therefore, accurate interpretation of blood pressure up to the error level as low as 5 mm of Hg is of supreme importance at the age of growing enigma of hypertensive disorders.

For correct estimation of BP in not-invasive setting Mercury sphygmomanometers are considered equally gold standard for long [5]. Just the fright of percious effect of potential mercury toxicity and the problems associated with disposal of mercury, has led to decrease use of mercury instruments worldwide. For the same reason European Matrimony directed phasing out of Mercury instruments recently [6]. Non-mercury sphygmomanometers similar aneroid and more recently, digital ones have replaced the use of traditional Mercury instruments in many settings. Additional reward of anaeroid musical instrument is the portability [7], while that of digital instruments are ease of use in view of the obvious fact that the latter obviates the need of auscultation skill of the examiner. In a large study at this outset in U.k. examined the comparability of measurement accurateness of all the three categories of sphygmomanometer and institute that digital instruments are almost as accurate as mercury instruments, while college failure rate existed with the aneroid ones and therefore the authors recommended the utilize of inexpensive and easy to apply digital instruments by full general practitioner during home visit [7]. Still, such evidences are scanty in Indian context, where there is an obvious need of more feasible and inexpensive instruments because of large population size, increased poverty and decreased tendency to seek institution based medical care.

Aim

In this context we conducted this study to compare the accuracy of readings of aneroid and digital sphygmomanometers in reference to mercury sphygmomanometers and determine the hypertensive nomenclature agreement betwixt the mercury and non-mercury devices.

Materials and Methods

This was a dispensary-based cantankerous-sectional analytical study to acquit diagnostic accuracy of two instruments: aneroid sphygmomanometer and digital sphygmomanometer. In an OPD of the primary health centre under the purview of our establish, we examined all the subjects in a higher place the age of 25 years, in two days per week, selected randomly from v working days per week in a flow of one month (January, 2015-February, 2015). The age criteria was selected then, because nosotros experienced 0% hypertension in the OPD amidst individual anile 25 years or less, who reported in the OPD in the previous i calendar month. The total number of participants was found to be 218. For the measurement of blood pressure level in each private we used 3 types of sphygmomanometers: The readings of Aneroid sphygmomanometer (MDF808B) and Digital sphygmomanometer (Omron Hem-7111) were compared to that of a mercury sphygmomanometer (NOVAPHON). All the instruments were checked, standardized and calibratedby experts. Approval of the Institutional Ethics Committee and informed consent from the written report participants were taken.

• Measurement of Blood Pressure level: Standard operating procedure for measuring blood pressure was followed [5]. It was ensured that the study participants were relaxed at-least for 10–15 min earlier measurements and were seated with legs uncrossed and back supported and arm was supported at heart level earlier the measurements. Cuffs of appropriate sizes were used [5]. Blood pressure of each participant was measured twice by each instrument and average of the two readings was noted down in a data entry course. All the private blood pressure measurements of the study participants were repeated at thirty second intervals.

Statistical Analysis

To notice out the mean difference of estimated blood pressures among all individuals by the three instruments, paired t-tests were performed. Agreement of measurement between aneroid and gold standard (mercury instrument) and betwixt digital and gold standard (mercury instrument) was analysed using kappa coefficient and sensitivity and specificity were estimated. Receiver Operating Characteristics (ROC) bend analyses were performed to detect out the accurateness of judge of the exam instruments (aneroid and digital) in reference to mercury musical instrument and respective cut-off values were determined past calculating Youden index.

Results

Mean age of the 218 individuals studied was 54.9 years. (±12.ix). The claret pressure measured by each non mercury device was compared with respect to the measurements done past the mercury musical instrument (gold standard).

one. Comparing the readings of claret pressure measured: [Table/Fig-1] shows the percent distribution of absolute differences of the readings between the mercury and not- mercury devices separately within 0-3, four-v, six-ten, 11-15 and 16+ mm Hg. categories. Accented agreements within five mm Hg. is considered the accepted threshold for credence of the accuracy of the equipment with respect to the gold standard equipment (mercury device) [viii]. In our study the accented departure inside v mm Hg. between mercury and aneroid for systolic and diastolic claret pressure were 89.iv% and 91.7% of the readings respectively. While the accented difference of inside v mm Hg. between mercury and digital for systolic and diastolic blood force per unit area were 25.2% and 43.six% of the readings respectively.

Bar graph showing the percentage distribution of the absolute differences of readings between the mercury and aneroid and between mercury and digital devices for measuring systolic and diastolic blood pressure level

For systolic and diastolic claret pressure treated separately the mean difference between the exam device and the mercury sphygmomanometer should be ±5 mm Hg or less, with a standard deviation of eight mm Hg or less [eight]. The correlation between the mercury readings and the aneroid device (r=0.98 systolic, r=0.84 diastolic: p<0.001 for both) and between mercury and digital device (r=0.95 systolic, r=0.67 diastolic: p < 0.001 for both) were statistically significant. The paired sample t-examination [Table/Fig-2] showed the hateful divergence between mercury and aneroid readings to be ane.v (SD 3.two) and one.8 (SD 2.9) for systolic and diastolic blood pressure level respectively, while the mean difference between mercury and digital device was – vii.2 (SD 10.1) and -2.0 (SD eight.3) for systolic and diastolic claret pressure respectively.

[Table/Fig-2]:

Means & Mean Difference of Blood Pressure (Systolic and Diastolic): Mercury Sphygmomanometer verses aneroid sphygmomanometer and Mercury sphygmomanometer verses digital sphygmomanometer (n=218).

Blood Pressure	Mercury: Hateful (SD)	Aneroid: Mean (SD)	Digital: Mean (SD)	Mercury vs aneroid: Mean departure (SD)	Mercury vs digital: Hateful difference (SD)
Systolic	139.7 (17.9)	138.2(17.six)	146.nine(18.4)	1.v(3.2)*	-7.2(ten.1)*
Diastolic	77.9 (9.4)	76.i (9.1)	79.9(10.vii)	1.8(ii.9)*	-two.0(eight.3)*

2. Comparison of devices on hypertension classification understanding: [Table/Fig-3] shows the agreement between the exam device with the mercury device while classifying the patients as hypertensives and not-hypetensives. Individuals having blood pressure more than 140/ninety mm Hg detected by mercury sphygmomanometer were considered to exist hypertensives. The kappa agreement were 0.88 and 0.39 for the aneroid and digital devices respectively (both were statistically significant). The aneroid device has correctly diagnosed 86.7% of hypertensives and 98.7% of normotensives whereas the digital device has correctly diagnosed 80.0% and 67.7% of normotensives.

[Tabular array/Fig-3]:

Diagnosis of hypertensive, by mercury and non-mercury (aneroid & digital) devices. (north=218)

Device and understanding			Mercury				Mercury
			Hypertension				Hypertension
			Yeah	No			Yes	No
Device	Aneroid	Yes	52	ii	Digital	Yes	48	51
		No	8	156		No	12	107
Understanding statistics
			Aneroid Device			Digital Device
Kappa			0.881			0.397
Sensitivity			86.7 %			80.0 %
Specificity			98.7 %			67.7 %
Positive predictive value			96.3%			88.9 %
Negative predictive value			95.1%			65.24 %
Likelihood ratio of positive test (LR+)			66.7			247.seven
Likelihood ratio of negative test (LR-)			0.13			0.3

[Table/Fig-4] shows the analysis of Receiver Operating Feature (ROC) curve (shown in [Tabular array/Fig-v]) which showed the area under the curve for systolic claret pressure level in aneroid and digital device was 0.94 (95% CI 0.91-0.97), 0.83 (95% CI 0.77-0.89) respectively whereas for diastolic blood force per unit area measured past aneroid and digital device was 0.85 (95% CI 0.79-0.91) and 0.7 (95% CI 0.62-0.78) respectively. In ROC curve assay more than the expanse under the curve, more than is the diagnostic accurateness of the exam. The results showed that the surface area under the curve for both systolic and diastolic blood pressures measured by aneroid devices was more than that of the measurements washed by digital device and it clearly depicts that, the diagnostic accuracy of aneroid sphygmomanometer was better than digital sphygmomanometer for measuring both systolic and diastolic blood pressures. The Youden index (sensitivity + specificity -1) which is calculated to detect the optimal threshold to detect a affliction from the data analysis of ROC bend was done. It showed (not shown in the table) that the optimal cut off of the readings of non-mercury sphygmomanometers to detect hypertension (with reference to the gold standard mercury sphygmomanometers) was different. In case of the aneroid devices if the blood pressure readings are more than 143/79 mm Hg and then the patient should be called to have hypertension while in instance of measurement past a digital device, a claret pressure reading above 149.5/84.five mm Hg should considered as the benchmark to classify the patient as hypertensive.

[Table/Fig-4]:

Comparison of the effect of Receiver operating feature curve (ROC) curves.

Blazon of device	Blood Pressure	Area under the curve (95% CI)	Optimal cut-off to detect Hypertension (Youden Index)
Aneroid	Systolic	0.94 (0.91-0.97)	143 mm Hg.
	Diastolic	0.85 (0.79-0.91)	79 mm Hg.
Digital	Systolic	0.83 (0.77-0.89)	149.v mm Hg.
	Diastolic	0.seventy (0.62-0.78)	84.five mm Hg.

Receiver operating characteristic curve (ROC) curves for Aneroid and Digital Systolic and Diastolic claret pressure measurements

A: Receiver operating characteristic curve (ROC) for systolic blood pressure level measured by aneroid device.

B: ROC for diastolic blood force per unit area measured by aneroid device.

C: ROC for systolic blood pressure measured past digital device.

D: ROC for diastolic blood pressure measured by digital device.

Discussion

The report was conducted to determine and compare the accurateness of non-mercury instruments and their power to correctly diagnose hypertension. An aneroid and a digital instrument were selected for the purpose and were judged with respect to a properly calibrated mercury sphygmomanometer (Gold standard).

The hateful difference and standard difference of the aneroid device is within the accepted threshold (±five mm Hg or less, with a standard deviation of 8 mm Hg or less) recommended by the Association for the Advancement of Medical Instrumentation guidelines (AAMI, 2008) [viii] simply the digital device failed to accomplish that. This suggested the superiority of aneroid devices with respect to digital instruments in accurately measuring blood pressure in primary care setting.

We also found that the agreement between the mercury and aneroid device in classifying hypertension was very high (kappa= 0.881, p<0.001). Yet, only moderate agreement was establish betwixt digital and mercury device (kappa= 0.397, p<0.001) in this respect. This suggested the greater ability of the aneroid instruments in classifying an individual as hypertensive or normotensive. This is particularly important because such nomenclature needs to exist very accurate so that all the diseased get the opportunity in receiving treatment and the not-diseased are not exposed to hazards related to cost and adverse effects of drugs and mental desperation considering of wrong diagnosis.

In the validity analysis we studied whether the aneroid and digital devices produced authentic results (1 that lacked systematic fault) by calculating sensitivity, specificity, positive and negative predictive value; the mercury device being considered equally a gilded standard. All the indicators showed better results for aneroid device in comparing to the digital device. The expanse under the ROC curve for both systolic and diastolic blood pressure level was much larger for aneroid than digital devices suggesting that aneroid device was amend detector of hypertension than the digital device. When we estimated the Youden index from the sensitivity and specifity of cut-offs, we also plant that for the detection of hypertension, the optimal cut off should be different for aneroid and digital device as in comparing to the standard 140/90 mm Hg. as measured past a mercury sphygmomanometer. This is important in the current context considering nosotros soon have same benchmark for detecting hypertension measured by all the devices.

The findings of our study were in contradiction to the findings of following studies conducted previously with similar objectives:

In a study done by NHANES the mean difference of SBP and DBP in the digital device compared to mercury device is -i.half-dozen (SD 6.8) and -1.6 (SD seven.8) and the Kappa for digital device is 0.72 [9]. Withal, such contradiction in findings may be attributed to the use of different model of the digital instrument.

In some other study among more than 8000 patients researchers used 604 sphygmomanometers (53% digital, 32% aneroid, 13% mercury and 2% hybrid devices). They institute that merely 78% of the aneroid models were able to requite accurate measures, while 88% digital devices were authentic, considering acceptable error of iii mm of Hg [seven]. In our study, we examined the accuracy of single musical instrument of each type and constitute the aneroid device to be superior than the digital device. This may be attributed to the stringent acceptable error criteria of the former study, which accepted only errors inside 3 mm oh Hg which was much narrower than our criteria of 5 mm of Hg. This caption can be substantiated with the findings of another report, in which researchers aimed to measure out the accuracy of 283 aneroid devices and found that 100% of the aneroid devices were accurate in estimating blood pressure inside the range recommended past the Clan for the Advancement of Medical Instrumentation [10]. In our written report we used the same criteria of acceptability. Some other potential reason of difference in finding may be that aneroid devices needed yearly maintenance. A yearly calibration with a standard of 2 mm of Hg error has been constitute to improve accuracy of the aneroid instrument [eleven]. In our study we used new, out-of-box instruments for measurement, which might have resulted in greater accuracy of aneroid device.

However, in a similar study like that of ours, only with a randomized single visit cross-over pattern, amid 95 individuals, researchers found the aneroid device performing much better than digital device. With same error criteria of 5 mm of Hg as that of our study, they plant that aneroid monitor could correctly judge 54% of the systolic and 58% of the diastolic claret pressures in comparing to only 34% of the correct systolic and 48% of the right diastolic measurement by digital instrument [12]. In some other study, with smaller sample size than that of our study, the researchers also observed that aneroid instruments were significantly more accurate than digital instruments of both arm and wrist type. The systolic blood pressure was particularly overestimated in example of arm blazon digital instruments [xiii]. The implication that the aneroid devices are more accurate would besides add to the prove substantiated in a review that measurement of blood force per unit area using aneroid devices are authentic provided the device maintenance and handling are conducted properly [14].

Use of more than advanced statistical techniques using ROC curve estimation, and Youden Index calculation, furthermore substantiated the evidence gathered from our study and we additionally found the evidence that aneroid devices were superior to digital devices in classifying hypertensive and non-hypertensive individuals apart from the findings of agreement of mean and kappa statistic.

The major strength of this written report was conducting research in primary care OPD setting, which has been fix as the offset opportunity of contact between people of the state and the medico in government system. Additionally blood force per unit area of each individual by all the 3 instruments was measured by a unmarried examiner, who was a doctor. This obviated the chance inter-rater difference in measurement of blood pressure. Thirdly, nosotros analysed the blood pressure of the individuals measured past three separate instruments past both norm reference and criterion reference analyses. Therefore, we were able to observe out the accuracy of exact measurement of the value of claret pressure besides every bit classify individuals between hypertensive and normotensive category. Fourthly, we estimated advisable cut-off values for both aneroid and digital instrument and this was never performed earlier while comparing the two instruments.

Limitation

The major limitation of the study was that it was conducted within the OPD climate, which carried with itself the chances of bias due to studying individuals seeking health service only, and the issue cannot be generalised to all individuals of the community. Secondly, we used only one instrument of each type and therefore from this study it is impossible to conclude the overall effectiveness of aneroid and digital instruments, when batches of instruments are used in institution. Thirdly, we performed the study in simply one health center, in ane season only. Considering possible error of aneroid BP in changing temperature and climate, larger written report volition exist needed encompassing multiple sites with different climate and in different fourth dimension of the year to conclusively compare the effectiveness of the two instruments; aneroid and digital.

Decision

Our study revealed the greater effectiveness of aneroid device in comparing to digital device in measuring blood pressure among individuals aged 25 years or more in the setting of primary health heart on out-patient basis. The findings implicated that the digital devices should be used with caution, incertitude and suspicion. If they are at all used, we propose that different cut-off level of hypertension should exist used for making right diagnosis of hypertension.

Finally, from our written report we conclude that the sensitivity and specificity of digital sphygmomanometers, though is piece of cake to use, requiring no expertise at all, are non upward to standard. If used in the customs for screening at that place will exist many people who either will be wrongly or misdiagnosed of hypertension. The field staff and the community itself are ofttimes attracted to utilize digital sphygmomanometer considering of its easy to utilize features requiring no expertise at all. If this instrument is taken up for employ past the health personnel for detection of hypertension it may prove disastrous as far as detection, management and treatment of hypertension are concerned.

Notes

Financial or Other Competing Interests

None.

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843288/

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