| Summary: | Background: Ambulatory blood pressure measurements are frequently lower compared to office measurements. Our aims were to investigate the relationship between office blood pressure measurements and ambulatory measurements and to quantify the difference between the two methods. Methods: This study included 1608 participants aged 50 – 62 years from the municipality of Tromsø, Norway. Office blood pressure measurements and ambulatory measurements were compared using the Bland-Altman plot, Deming regression, and paired sample t-test. The Pearson correlation coefficient was also calculated. Results: The mean (standard deviation) daytime ambulatory systolic and diastolic blood pressure were 130.2 mmHg (13.2) and 82.1 mmHg (8.7), respectively. The mean systolic and diastolic observed office blood pressure was 129.6 mmHg (17.7) and 83.4 mmHg (9.8), respectively. Office diastolic blood pressure was significantly higher than ambulatory diastolic blood pressure (P<0.001). In the Bland-Altman plot, office systolic blood pressure was on average 0.53 mmHg lower than daytime ambulatory systolic blood pressure, and office diastolic blood pressure was on average 1.33 mmHg higher than daytime ambulatory diastolic pressure. In Deming regression, for each unit increase in ambulatory systolic blood pressure and ambulatory diastolic blood pressure, office systolic blood pressure increased with 0.68 mmHg (P<0.01) and office diastolic blood pressure increased with 0.85 mmHg (P<0.01), respectively. The Pearson R correlation between daytime ambulatory and office systolic blood pressure, and daytime ambulatory and office diastolic blood pressure was 0.73 (P<0.01) and 0.72 (P<0.01), respectively. Conclusion: We found significantly higher observed office diastolic blood pressure compared to ambulatory diastolic blood pressure. However, the difference was small and probably not clinically significant for the individual patient. The blood pressure measurements conducted by trained study nurses are not directly comparable to ...
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