Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Accuracy of blood pressure measurement: sphygmomanometer calibration and beyond Gianfranco Parati a,b , Andrea Faini a and Paolo Castiglioni c Journal of Hypertension 2006, 24:1915–1918 a Department of Clinical Medicine and Prevention, University of Milano-Bicocca, Milan, b II Cardiology Unit, San Luca Hospital, IRCCS, Istituto Auxologico Italiano, Milan and c Bioengineering Center, Don C. Gnocchi Foundation, IRCCS, Milan, Italy Correspondence and requests for reprints to Gianfranco Parati, Department of Cardiology, San Luca Hospital, Istituto Auxologico Italiano, Via Spagnoletto, 3, 20149 Milan, Italy Tel: +39 02 619112890; fax: +39 02 619112956; e-mail: gianfranco.parati@unimib.it See original paper on page 1931 The importance of accurate blood pressure measurement in the diagnosis of arterial hypertension, and in the precise titration of antihypertensive treatment, is largely acknowledged in clinical practice. The relevance of this issue has recently been further emphasized by hyper- tension management guidelines [1 – 3]. Health care givers as well as patients are now aware of the need to follow carefully standardized procedures when measuring blood pressure, aimed at achieving the highest possible accuracy of blood pressure estimates. Conversely, the possible negative impact that poor main- tenance of blood pressure-measuring devices may have on the accuracy of patients’ blood pressure assessment, is still largely underestimated or disregarded, even by physicians and nurses. This phenomenon should be considered with concern because a technical problem such as sphygmomanometer calibration might impor- tantly affect the effectiveness of hypertension manage- ment and, surprisingly enough, its influence may be greater now than some years ago. This is due to the more and more frequent tendency among hospital staff and general practitioners to shift from use of the classical mercury sphygmomanometer to the adoption of other blood pressure-measuring techniques, such as aneroid sphygmomanometers and electronic devices. In this issue of the journal, Turner et al. [4] provide further evidence to support the clinical relevance of sphygmomanometer calibration. By means of mathe- matical simulations, the authors have extended the results of previous studies [5,6], and have estimated the combined effects exerted on the detection of arterial hypertension by random blood pressure variability (including intra-individual blood pressure variability as well as random measurement errors) and by systematic errors due to inadequate sphygmomanometer calibration. The main findings of their mathematical simulation are summarized in Fig. 2 of their paper [4]. The percent- age of subjects correctly labelled as hypertensives (a measure of the sensitivity of the diagnostic procedure) increased significantly with the increase in the number of doctor’s visits, when correctly calibrated blood pressure- measuring devices were employed. This increase reflects a reduction in random error obtained by averaging the blood pressure values measured over successive visits. Conversely, when non-calibrated devices were used not only the sensitivity of the diagnostic procedure was lower at the first visit, but also the increment in sensitivity with repeated visits, observed over subsequent measurements when using calibrated manometers, was less pronounced. This is because the non-calibrated sphygmomanometer introduces a systematic error in the blood pressure esti- mate that cannot be reduced by averaging several measurements. Because of this, the sensitivity curves typical of calibrated and of non-calibrated devices dis- played a tendency to diverge with the increase in the number of visits. A specific feature of the study by Turner et al. [4], which deserves some discussion, is represented by the mathe- matical model employed to assess the clinical relevance of sphygmomanometer calibration, a model which may not necessarily be familiar to some researchers. The authors used a simple Monte Carlo simulation to estimate the combined effects of systematic sphygmomanometer error and day-to-day random variability of blood pressure measurements on the over- and under-detection of hy- pertension in adults aged 18 years and older. Monte Carlo methods are a class of computational algorithms for simulating the behaviour of various physical and mathe- matical systems. These techniques are used in situations where the analytic solution of a problem is either hardly achievable or time consuming. In other words, a Monte Carlo algorithm is a method used to find solutions to mathematical problems (which may be characterized by many variables) that cannot easily be solved, for example, by integral calculus, or by other numerical methods. Its efficiency when compared with other numerical methods increases with the increase in the dimension of the problem to be solved. A Monte Carlo technique can be differentiated from other simulation methods because of its stochastic nature (i.e. because it is characterized by non-deterministic algorithms, through use of random numbers). Monte Carlo techniques have a long history in math- ematics, with their earliest application probably being Editorial comment 1915 0263-6352 ß 2006 Lippincott Williams & Wilkins