Bodil Gade Hornstrup, Jeppe Bakkestrøm Rosenbæk, Jesper Nørgaard Bech University Clinic in Nephrology and Hypertension, Regional Hospital West Jutland and Aarhus University, Holstebro, DenmarkCorrespondence: Bodil Gade HornstrupUniversity Clinic in Nephrology and Hypertension, Regional Hospital West Jutland and Aarhus University, Holstebro, DenmarkEmail bodil.hornstrup@rm.dkAim: Correct measurement of blood pressure (BP) is important for optimal diagnosis and treatment of patients with hypertension. The aim of this study was to compare a wrist-worn device using tonometric measurements of BP to a conventional device using oscillometric measurements of 24 h BP, diagnosing of hypertension, and non-dipping.Methods: One-hundred patients in the Renal Outpatient Clinic had 24 h ambulatory BP monitoring performed with a tonometric device, BPro, and an oscillometric device, A&D, simultaneously.Results: Twenty-four-hour and daytime systolic BP was significantly lower using tonometric monitoring compared to oscillometric (7 and 6 mmHg, respectively, p< 0.001). In the population of patients diagnosed with hypertension, the tonometric device diagnosed 90% of patients with uncontrolled hypertension correctly (positive predictive value), whereas 49% of patients classified as normotensive were uncontrolled hypertensive (negative predictive value). The mean difference between relative nocturnal BP decrease between tonometric and oscillometric was 2± 8% (p< 0.01), and 33% of patients classified as dippers were non-dippers (negative predictive value).Conclusion: Using the BPro device for tonometric monitoring of BP and classification of hypertension and non-dipping in patients diagnosed with hypertension leads to misclassification of patients. Therefore, the BPro device is not suitable for clinical practice in hypertensive patients from a Renal Outpatient Clinic.Keywords: ambulatory blood pressure monitoring, oscillometric, tonometric