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Blood pressure measurements by the Keito machine. Evaluation versus office blood pressure by physicians

Staal, Eva M.a; Nygård, Ottar K.a b; Omvik, Perb; Gerdts, Evaa b

doi: 10.1097/01.mbp.0000130223.80658.3d
Devices and Technology

Background The Keito machine offers automatic measurements of blood pressure (BP), height and weight on insertion of coins and has been introduced in pharmacies.

Design Cross-sectional study comparing automatic BP measurements by the Keito machine to office BP measurements by physicians.

Methods Patients scheduled for pre-catheterisation screening participated in the study. Their BP was first measured using the Keito machine, then by physicians. Office BP was recorded as the last of three consecutive BP measurements recorded with one-min intervals after a five-min rest in the sitting position. In a sub-study BP was measured simultaneously during the Keito measurement by a physician.

Results In 390 consecutive patients average BP was significantly lower with the Keito machine compared to office BP measurements made by the physicians (136/75±19/8 mmHg versus 141/79±21/10 mmHg, both p<0.001). The correlation coefficient (r) was 0.56 (p<0.001) for systolic BP (SBP) and 0.53 (p<0.001) for diastolic BP (DBP). Bland-Altman analysis showed a mean difference (±2 SD) for SBP and DBP of –5 (±37) and –4 (±17) mmHg, respectively. When defining hypertension (HT) as office SBP≥140 and/or DBP≥90 mmHg, the Keito method diagnosed 83% of the systolic and 62% of the diastolic hypertensive population correctly. The classification of systolic and diastolic normotensive was correct in 61% and 86%, respectively.

Conclusion Agreement between office and Keito BP is poor. The Keito machine underestimates SBP on average by 5 mmHg and DBP by 4 mmHg, which may be of significance for diagnosing HT and starting anti-hypertensive therapy. However, the difference can be much larger in individual patients. Therefore, the Keito machine cannot be recommended for medical screening of HT or as a replacement for follow-up by physicians.

aDepartment of Heart Disease

bInstitute of Medicine, Haukeland University Hospital, Bergen, Norway

Correspondence and requests for reprints to Eva Gerdts, MD, PhD, Department of Heart Disease, Haukeland University Hospital, Jonas Liesvei 65, 5021 Bergen, Norway.

Tel: +47 5597 2170; fax: +47 5597 5150;


Received 21 October 2003 Revised 20 February 2004 Accepted 02 March 2004

© 2004 Lippincott Williams & Wilkins, Inc.