Quality is not an act, it is a habit—Aristotle

To measure blood pressure precisely and make the data comparable among facilities, measurement methods and devices must be standardized. Since the Minamata Convention on Mercury, there is no metrological standard for sphygmomanometers. The current validation methods recommended by non-profit organizations in Japan, the US, and European Union countries are not necessarily applicable to the clinical setting, and no protocol for daily or routine performance of quality control has been defined. In addition, recent rapid technological advances have enabled monitoring blood pressure at home with wearable devices or without a cuff by using a smartphone app. A clinically relevant validation method for this recent technology is not available. The importance of out-of-office blood pressure measurement is highlighted by guidelines for the diagnosis and treatment of hypertension, but an appropriate protocol for validating a device is required. [Image: see text]