Impact of Miscuffing During Home Blood Pressure Measurement on the Prevalence of Masked Hypertension

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1 Brief Communication Impact of Miscuffing During Home Blood Pressure Measurement on the Prevalence of Masked Hypertension Jean-Jacques Mourad, 1 Marilucy Lopez-Sublet, 1 Sola Aoun-Bahous, 2 Frédéric Villeneuve, 3 Olivier Jaboureck, 4 Caroline Dourmap-Collas, 5 Thierry Denolle, 6 Jacques Fourcade, 7 and Jean-Philippe Baguet 8 background Masked hypertension has been associated with obesity. However, because most studies do not mention the specific cuff size used for home measurements, masked hypertension prevalence may have been overestimated in obese patients because of undersized cuffs. In this prospective, observational study, the effect of miscuffing on hypertension status was evaluated in patients with large arms. methods Fifty-three patients with an upper-arm circumference >33 cm, undergoing treatment for mild-to-moderate hypertension, took 2 sets of home blood pressure (BP) measurements (standard vs. large cuff) using the validated Microlife BP A100 Plus automated device. results Mean BP was 143/85 mm Hg at the office using a large cuff, 141/84 mm Hg at home using a standard cuff, and 134/80 mm Hg at home using a large cuff. Standard vs. large cuff home BP mean differences were 6.9 mm Hg (95% confidence interval (CI) = ; P < ) for systolic BP and 4.0 mm Hg (95% CI = ; Because hypertension is a risk factor for cardiovascular events and has significant prognostic value, much effort has been invested into establishing accurate, reproducible methods for measuring blood pressure (BP). Guidelines repeatedly underscore the importance of appropriate measuring techniques and provide extensive recommendations for proper positioning, number of measurements, cuff choice, and verification of office measurements with home monitoring systems. 1,2 In recent years, guidelines have put growing emphasis on automated oscillometric devices because they are used for home-based BP measurement and are slowly replacing office mercury sphygmomanometers. 3 Correspondence: Jean-Jacques Mourad (jean-jacques.mourad@avc. aphp.fr). Initially submitted March 1, 2013; date of first revision May 13, 2013; accepted for publication May 14, 2013; online publication June 1, P < ) for diastolic BP. Hypertension status differed significantly between standard vs. large cuffs: sustained hypertension (56.6% vs. 41.5%, respectively; P = 0.002), controlled hypertension (20.8% vs. 28.3%, respectively; P = 0.04), white coat hypertension (7.5% vs. 22.6%, respectively; P = 0.002), masked hypertension (15.1% vs. 7.5%, respectively; P = 0.04). conclusions In patients with large arms, use of an appropriately sized large cuff for home BP measurements led to a 2-fold reduction in masked hypertension. Regarding clinical and epidemiological implications, future studies investigating masked hypertension should specify cuff size for home BP measurements. The low market availability and increased cost of large cuffs should also be addressed. Keywords: blood pressure; blood pressure determination; cuff size; diagnostic errors; hypertension; isolated clinic hypertension; masked hypertension; obesity; white coat hypertension. doi: /ajh/hpt084 Specifically, home BP and ambulatory BP monitoring are recommended in patients with mild-to-moderate hypertension to confirm office readings, to assess white coat and masked hypertension, to monitor BP variations throughout the day, and to improve treatment results. 1,2 This clinical approach is supported by studies conducted in a wide range of patients. 2,4 11 For example, in the Self measurement of blood pressure at Home in the Elderly: Assessment and Follow-up (SHEAF) study of elderly patients with mild hypertension, 12.5% had white coat hypertension and 10.8% had masked hypertension. 4,5 In a recent literature review, the estimated prevalence of masked hypertension was 8% 20% 1 Excellence Center for Hypertension, CHU Avicenne, AP-HP, Bobigny, France; 2 Department of Nephrology, St George Hospital, Beirut, Lebanon; 3 Hypertension Unit, CHU Pitié-Salpêtrière, AP-HP, Paris, France; 4 Department of Cardiology, Douai Hospital, Douai, France; 5 Department of Cardiology, CHU Pontchaillou, Rennes, France; 6 Department of Cardiology, CH Dinard, France; 7 Department of Nephrology, CH Chambery, Chambery, France; 8 Department of Cardiology, CHU Albert Michallon, Grenoble, France. American Journal of Hypertension, Ltd All rights reserved. For Permissions, please journals.permissions@oup.com American Journal of Hypertension 26(10) October

2 Mourad et al. and up to 50% in treated patients. 5 Thus, home monitoring can identify patients with masked hypertension, which is clinically significant because the risk of cardiovascular events in patients with masked hypertension is similar to that of patients with uncontrolled hypertension. 5 The prognostic value of home BP measurements is also significantly greater than the prognostic value of office measurements. 8,9 Cuff size also affects BP measurement accuracy. Indeed, office-based studies demonstrate that undersized cuffs can overestimate BP and, conversely, that oversized cuffs can underestimate BP Ideally, cuffs should have a 2:1 lengthto-width ratio, with the length of the inflatable bladder covering at least 80% of the circumference of the arm; 2 however, the use of inappropriately sized cuffs is a common error during BP measurement. 1 With the general increase in upper-arm circumference due to increasing obesity among Western populations, 15,16 use of standard cuffs is not appropriate for significant numbers of patients. In obese patients, who are at high cardiovascular risk, BP has been overestimated because of the use of undersized cuffs. 13,14 Consequently, the European Society of Hypertension (ESH) has extended recommendations about cuff size for office measurements to include home settings. 2 However, excepting a small industry-sponsored study in 22 obese patients, 17 the impact of cuff size on home BP measurements in patients with large arm circumferences has not been evaluated. In this study, we quantified the impact of undersized cuffs on home BP measurements in patients with upper-arm circumferences >33 cm. METHODS In this observational, home BP measurement study, each patient recorded 2 sets of BP measurements. In each set, 3 consecutive measurements (with a delay of <1 minute between each measurement) were undertaken in the morning at approximately breakfast time and again in the evening before going to bed. Measurements were undertaken over 3 consecutive days, giving a total of 18 measurements per set. Patients born in an even year were assigned standard cuffs for the first set of measurements and large cuffs for the second set of measurements and vice versa for patients born in odd years. The 2 measurement sets needed to be taken within a 2-week period, preferably on the same 3 consecutive days of the 2 consecutive weeks. Each investigator had to enroll a minimum of 10 patients. The study was conducted in accordance with the Declaration of Helsinki. Patients were informed that the purpose of the study was to assess differences in BP measurement using 2 different cuffs. Inclusion and exclusion criteria Outpatients who were being treated for mild-to-moderate hypertension and who had a non-dominant arm circumference >33 cm were enrolled if they had been on a stable antihypertensive treatment for at least 15 days before inclusion, if no changes in antihypertensive treatment were planned during the duration of the study, and if they had provided informed consent. Patients with arrhythmias (atrial fibrillation or numerous extrasystoles) were excluded American Journal of Hypertension 26(10) October 2013 BP measurements Each physician was given 1 upper-arm automatic BP monitor (BP A100 Plus; Microlife, Widnau, Switzerland) with a large cuff (L-size Microlife cuff, inflatable bladder length 33 cm, for an arm circumference of cm). Three consecutive office BP measurements (with a delay of <1 minute between each measurement) were performed by trained physicians during the inclusion visit, beginning after a 5-minute rest period using the BP A100 Plus device and a large cuff on the nondominant forearm with the patient in the seated position. Patients were given the same BP A100 Plus monitor with a large cuff (as above) and a standard cuff (M-size Microlife cuff, inflatable bladder length 26 cm, for an arm circumference of cm). For home measurements, patients were instructed to measure BP in a relaxed sitting position, after 5 minutes of rest, and with the nondominant forearm resting comfortably on the table where the monitor was placed. Patients were told to position cuffs in the same place on the nondominant arm for every measurement. Patients recorded their measurements on study report forms and returned them to their physician after the 2-week period. All monitors were new, from the same batch, and specifically provided for the study. The BP A100 Plus model was chosen because it meets ESH recommendations, has been validated according to the international protocol of the ESH, and can be used with different-sized cuffs. 2,18,19 Statistical analysis Office BP represented the average of 3 measurements, and home BP represented the average of 18 measurements per set. Hypertension in the office and at home was defined according to ESH guidelines, with a systolic BP (SBP) 140 and/or a diastolic BP (DBP) 90 mm Hg for office measurements and a SBP 135 and/or a DBP 85 mm Hg for home measurements. 2 Patients with sustained hypertension were defined as patients with uncontrolled BP in the office and home settings. Patients with controlled hypertension were defined as treated patients with controlled BP in the office and at home. Patients with white coat hypertension were defined as patients with uncontrolled office BP but controlled home BP. Patients with masked hypertension were defined as patients with controlled office BP but uncontrolled home BP. Patients with missing BP measurements were excluded from the analysis. All statistical analyses were performed using R (R Foundation for Statistical Computing, Vienna, Austria). Descriptive statistics were calculated for quantitative variables. Mean differences between standard vs. large cuff size measurements and their associated 95% confidence intervals (CIs) and 2-sided P values were calculated using paired t tests. Statistical significance for differences in numbers of patients classified as having controlled hypertension in the home setting was evaluated using the McNemar test (and in the case of <5 observations in any cell, an exact version). Between-cuff differences in proportions of patients with sustained, controlled, whitecoat, and masked hypertension and their associated 95% CI

3 Miscuffing and masked hypertension and 2-sided P values were calculated using the R package PropCIs (PropCIs: various confidence interval methods for proportions; R package version 0.2-0; The relationship between between-cuff mean differences in systolic BP and potential explanatory variables of interest were investigated using an analysis of variance and Tukey honestly significant difference testing (HSD) with terms for main effects of age ( 60 years vs. <60 years), sex (female vs. male), body mass index (BMI; 35 kg/m 2 vs. <35 kg/m 2 ), and arm circumference ( 36 cm vs. <36 cm) and terms for their associated 2-way interactions. Statistical significance was determined at the level of α = 0.05, unadjusted for multiple comparisons. RESULTS Fifty-three patients with a mean age of 60 ± a SD of 13 years were included in the analysis. Twenty-four patients were women (45.3%). The mean BMI was 36.0 ± 5.0 kg/m 2, and 88.5% of patients had a BMI 30 kg/m 2. Mean arm circumference was 36.3 ± 2.7 cm. Two patients had an arm circumference >42 cm. Mean office SBP was 143 ± 17 mm Hg, and mean office DBP was 85 ± 11 mm Hg, and office hypertension was controlled in 19 patients (35.8%). Mean home SBP was 141 ± 14 mm Hg and DBP was 84 ± 11 mm Hg with a standard cuff, and mean home SBP was 134 ± 13 mm Hg and DBP was 80 ± 10 mm Hg with a large cuff (Figure 1A). The between-cuff mean difference (standard minus large) was 6.9 mm Hg (95% CI = ; P < ) for SBP and 4.0 mm Hg (95% CI = ; P < ) for DBP. Differences ranged from 8 mm Hg to +28 mm Hg for a Home blood pressure ± SD,mm Hg Standard cuff a Systolic Large cuff b Diastolic b Proportion of patients, % c 56.6 SBP and from 5 mm Hg to +29 mm Hg for DBP. In 20 of 53 patients, the difference in SBP was >10 mm Hg. Home BP was controlled in 15 patients (28.3%) using the standard cuff and in 27 patients (50.9%) using the large cuff (P < 0.001). Hypertension status differed significantly depending on cuff size (Figure 1B). The proportion of patients with sustained hypertension was higher with the standard vs. the large cuff (56.6% vs. 41.5%, respectively), resulting in a difference of 15.1 percentage points (95% CI = ; P = 0.002). The proportion of patients with controlled hypertension was lower with the standard vs. the large cuff (20.8% vs. 28.3%, respectively), resulting in a difference of 7.5 percentage points (95% CI = 14.7 to 0.4; P = 0.04), and the proportion of patients with white coat hypertension was also lower with the standard vs. the large cuff (7.5% vs. 22.6%, respectively), resulting in a difference of 15.1 percentage points (95% CI = 24.7 to 5.5; P = 0.002). The proportion of patients with masked hypertension was higher with the standard cuff than with the large cuff (15.1% vs. 7.5%, respectively), resulting in a difference of 7.5 percentage points (95% CI = ; P = 0.04). The exploratory analysis of factors potentially predicting between-cuff mean differences in systolic BP showed that female sex was associated with a larger difference (10.1 mm Hg) than male sex (3.4 mm Hg) (female male difference = 6.7 mm Hg, 95% CI = ; P = 0.005), whereas age, BMI, or arm circumference main effects were not significant. However, Tukey HSD comparisons for interactions showed that older women (aged 60 years) had significantly larger between-cuff mean differences in systolic BP than younger men (aged <60 years), women who were very obese (BMI 35 kg/m 2 ) had significantly larger values than men who were less obese (BMI <35 kg/m 2 ), and women with 41.5 Sustained hypertension Standard cuff (home), large cuff (office) Large cuff (home), large cuff (office) d e f Controlled White Coat Masked hypertension hypertension hypertension Figure 1. Influence of cuff size on home blood pressure values and hypertension status. A) Home blood pressure by cuff size and B) Hypertension status by cuff size. Each patient (N = 53) recorded 2 sets of home blood pressure measurements: 1 set with a standard cuff and 1 set with a large cuff. Office blood pressure measurements were performed with a large cuff. a Between-cuff mean difference (standard minus large) = 6.9 mm Hg (95% confidence interval (CI) = ; P < ) and b 4.0 mm Hg (95% CI = ; P < ). c Between-cuff difference in proportions (standard minus large) = 15.1 percentage points (95% CI = ; P = 0.002), d 7.5 percentage points (95% CI = 14.7 to 0.4; P = 0.04), e 15.1 percentage points (95% CI = 24.7 to 5.5; P = 0.002), and f 7.5 percentage points (95% CI = ; P = 0.04). American Journal of Hypertension 26(10) October

4 Mourad et al. very large arm circumferences ( 36 cm) had significantly larger values than men with less large arm circumferences (<36 cm). See Supplementary Data online for further details. Discussion Our study demonstrated that for home BP measurement, the use of an appropriately sized large cuff for patients with an arm circumference >33 cm rather than a standard-sized cuff led to an overall reduction in BP readings, a 2-fold reduction in the number of patients with masked hypertension, and a 3-fold increase in the number of patients with white coat hypertension. The long-term public health ramifications of therapeutic decisions based on measurements made with wrong cuff sizes should be addressed, especially considering the rise in obesity, the increase in proportion of individuals with an arm circumference >33 cm, 15,16 and the fact that large cuffs are underused due to high cost and low availability. 20 For patients with an arm circumference >33 cm, the use of standard cuffs to measure BP in a home setting introduced significant error. In 20 of 53 patients, a difference of >10 mm Hg was recorded. Consequently, the percentage of patients who had not reached BP targets was 71.7% (sustained hypertension + masked hypertension) when measured with a standard cuff, whereas it was 49.0% when measured with a large cuff a finding likely to bias therapeutic decisions toward overtreatment. This risk has been noted in home BP measurement guidelines; however, the data upon which these guidelines were based were obtained from office measurements. 2,12 14,18 The 2-fold decrease (15.1% to 7.5%) in the prevalence of masked hypertension with an appropriately sized cuff is of particular note because it highlights the current misunderstanding about the putative relationship between masked hypertension and obesity. Although the pathophysiology of masked hypertension is not entirely understood, its reported prevalence increases markedly in obese patients. 6,7,11 For example, in white-collar workers, 13.2% of individuals with a BMI <27 kg/m 2 had masked hypertension compared with 18.3% with a BMI 27 kg/m However, because the aforementioned study and many others describing home and automated BP measurements do not specify the use of appropriately sized cuffs for obese patients, 2,4,5,21,22 BP readings in home settings were likely to have been overestimated. Our finding that female sex was associated with significantly greater between-cuff mean differences in SBP than male sex, whereas age, BMI, or arm circumference main effects were not, suggested that factors other than arm circumference might determine these between-cuff differences. However, Tukey HSD comparisons for interactions suggested that cuff size may be of particular importance for older female patients who are very obese or who have very large arm circumferences. These exploratory findings warrant further investigation in a larger sample and using a greater range of putative variables, such as magnetic resonance imaging determination of upper arm subcutaneous adipose tissue volume 23 because the degree of subcutaneous adiposity may be a relevant factor affecting upper-arm compressibility, especially given the greater subcutaneous adiposity in women compared with men. 24 A potential limitation of our study was that patients recorded measurements on case report forms that were then given to physicians. Patient reporting of BP can be subject to significant error. For example, in a study of 30 hypertensive patients comparing automatically stored BP readings with the respective logbook entries, 36% of patients underreported how many BP measurements were taken, 9% overreported them, and 24% reported imprecise values. 25 Therefore, our findings may have been affected by some degree of underreporting and/or imprecision. In conclusion, use of appropriately sized cuffs significantly reduces the proportion of obese patients classified with masked hypertension. Because BP readings significantly affect clinical decisions about cardiovascular health, these results underscore the importance of using proper measurement equipment. Furthermore, this study suggests that the reported prevalence of masked hypertension in obese patients could be overestimated in the literature and, consequently, that the reported association between obesity and masked hypertension may be an artifactual finding introduced by miscuffing. SUPPLEMENTARY MATERIAL Supplementary materials are available at American Journal of Hypertension ( Acknowledgments This work was supported by the Club des Jeunes Hypertensiologues, Avrainville, France. Medical writing assistance was provided by Springer Healthcare, which was funded by the Club des Jeunes Hypertensiologues. Disclosure The authors declared no conflict of interest. References 1. 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