Traditional methods for testing BP no longer adequate — study

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BloodpressureTraditional methods of testing for high-blood pressure are no longer adequate and risk missing vital health signs, which can lead to premature death, a study co-led by University College London (UCL) has found. The research, the largest ever cohort study of its kind, assessed 63,000 doctors’ patients, who had their blood pressure tested using traditional ‘in clinic’ methods, such as an automated or hand operated devices.

Separately, the same patients, were also measured using a pocket-sized ambulatory blood pressure monitoring (ABPM) device, which records blood pressure regularly across a 24-hour period. This device is worn at home and takes measurements every 20 to 30 mins.

High blood pressure is the leading preventable cause of premature death globally and affects approximately 25% of all adults. The study, which was co-led by Professor Bryan Williams (UCL Institute of Cardiovascular Sciences), found that measuring blood pressure using an ABPM device was 50% more accurate than the traditional way blood pressure is measured in the clinic, and therefore a significantly more accurate way of predicting a patient’s risk of death.

Using an ABPM to measure the blood pressure at home, during day-to-day activities and during sleep, also means known variations in patients’ blood pressure caused by using ‘in clinic’ methods, can be more accurately diagnosed. Namely ‘masked hypertension’, where blood pressure presents as normal in the clinic, but is elevated out of office, and ‘white-coat hypertension’, where blood pressure is elevated in the clinic, but normal outside the office.

“For decades doctors have known that blood pressure measured ‘in-clinic’ could be masked or elevated, simply because the patient was in a medical setting, and this could lead to the wrong or a missed diagnosis,” Williams said.

“This research is a clear game-changer, as for the first time, it definitively shows that blood pressure measured regularly during a 24-hour period predicts the risk of heart disease, stroke and death much better than blood pressure measured in a doctor’s surgery or clinic.

“Quite simply, measuring blood pressure over 24 hours is what doctors and medics should be using to make clinical decisions about treatment.

“With a much more accurate assessment of a patient’s blood pressure, doctors will be able to provide the most effective treatments at the earliest opportunity, which will save many more lives.

“With 1bn people around the world having high blood pressure, this study, the largest ever of its kind, should lead to changes in clinical practice across the world, with the use of ABPM becoming much more common place.”

William’s research is supported by the National Institute for Health Research UCLH Biomedical Research Centre. The cohort study, assessed over 60,000 patients who attended primary care in Spain and covers a period of around 10 years.

The research was promoted by the Spanish Society of Hypertension and has been conducted by researchers from the Universidad Autónoma de Madrid, health centres and other universities of Madrid, Asturias, Barcelona, the CIBERs of Epidemiology and Public Health and of Cardiovascular Research in Madrid, and UCL, in London.

Abstract
Background: Evidence for the influence of ambulatory blood pressure on prognosis derives mainly from population-based studies and a few relatively small clinical investigations. This study examined the associations of blood pressure measured in the clinic (clinic blood pressure) and 24-hour ambulatory blood pressure with all-cause and cardiovascular mortality in a large cohort of patients in primary care.
Methods: We analyzed data from a registry-based, multicenter, national cohort that included 63,910 adults recruited from 2004 through 2014 in Spain. Clinic and 24-hour ambulatory blood-pressure data were examined in the following categories: sustained hypertension (elevated clinic and elevated 24-hour ambulatory blood pressure), “white-coat” hypertension (elevated clinic and normal 24-hour ambulatory blood pressure), masked hypertension (normal clinic and elevated 24-hour ambulatory blood pressure), and normotension (normal clinic and normal 24-hour ambulatory blood pressure). Analyses were conducted with Cox regression models, adjusted for clinic and 24-hour ambulatory blood pressures and for confounders.
Results: During a median follow-up of 4.7 years, 3808 patients died from any cause, and 1295 of these patients died from cardiovascular causes. In a model that included both 24-hour and clinic measurements, 24-hour systolic pressure was more strongly associated with all-cause mortality (hazard ratio, 1.58 per 1-SD increase in pressure; 95% confidence interval [CI], 1.56 to 1.60, after adjustment for clinic blood pressure) than the clinic systolic pressure (hazard ratio, 1.02; 95% CI, 1.00 to 1.04, after adjustment for 24-hour blood pressure). Corresponding hazard ratios per 1-SD increase in pressure were 1.55 (95% CI, 1.53 to 1.57, after adjustment for clinic and daytime blood pressures) for nighttime ambulatory systolic pressure and 1.54 (95% CI, 1.52 to 1.56, after adjustment for clinic and nighttime blood pressures) for daytime ambulatory systolic pressure. These relationships were consistent across subgroups of age, sex, and status with respect to obesity, diabetes, cardiovascular disease, and antihypertensive treatment. Masked hypertension was more strongly associated with all-cause mortality (hazard ratio, 2.83; 95% CI, 2.12 to 3.79) than sustained hypertension (hazard ratio, 1.80; 95% CI, 1.41 to 2.31) or white-coat hypertension (hazard ratio, 1.79; 95% CI, 1.38 to 2.32). Results for cardiovascular mortality were similar to those for all-cause mortality.
Conclusions: Ambulatory blood-pressure measurements were a stronger predictor of all-cause and cardiovascular mortality than clinic blood-pressure measurements. White-coat hypertension was not benign, and masked hypertension was associated with a greater risk of death than sustained hypertension. (Funded by the Spanish Society of Hypertension and others.)

Authors
José R Banegas, Luis M Ruilope, Alejandro de la Sierra, Ernest Vinyoles, Manuel Gorostidi, Juan J de la Cruz, Gema Ruiz-Hurtado, Julián Segura, Fernando Rodríguez-Artalejo, Bryan Williams

University College London material
New England Journal of Medicine abstract


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