Standing orthostatic blood pressure measurements cannot be replaced by sitting measurements.

As many elderly patients are not able to stand for several minutes, sitting orthostatic blood pressure (BP) measurements are sometimes used as an alternative. We aimed to investigate the difference in BP response and orthostatic hypotension (OH) prevalence between the standard postural change to the sitting and the standing position in a cross-sectional observational study. BP was measured with a continuous BP measurement device during two postural changes, from supine to the sitting and from supine to the standing position. Linear mixed models were used to investigate the differences in changes (Δ) of systolic BP (SBP) and diastolic BP (DBP) between the two postural changes. The prevalence and the positive and negative proportions of agreement of OH were calculated of the two postural changes. One hundred and four patients with a mean age of 69 years were included. ΔSBP was significantly larger in the standing position compared with the sitting between 0 and 44 s. ΔDBP was significantly larger in the sitting position compared with the standing 75-224 s after postural change. The prevalence of OH was 66.3% (95% confidence interval (CI) 57.2, 75.4) in the standing position and 67.3% (95% CI 58.3, 76.3) in the sitting position. The positive proportion of agreement was 74.8% and the negative proportion of agreement was 49.3%. A clear difference was seen in BP response between the two postural changes. Although no significant difference in prevalence of OH was observed, the positive and negative proportion of agreement of the prevalence of OH were poor to moderate, which indicates a different outcome between both postural changes.