The diagnostic value of supine blood pressure in hypertension

Abstract

Introduction: Correct blood pressure (BP) measurement is crucial in the diagnosis of arterial hypertension (AH), and controversy exists whether supine BP should be treated as equal to sitting BP. The aim of this study was to evaluate the relation of supine BP to sitting BP and ambulatory BP with regard to identification of diagnostic cut-offs for hypertension.

Material and methods: This study included 280 patients with AH (mean age: 44.3 ±10.6 years). The following measurements of BP were performed and analyzed: 1) sitting office blood pressure measurement (OSBP and ODBP); 2) supine BP (supSBP and supDBP), measured automatically (5 times with a 2-minute interval) during evaluation by the Niccomo device (Medis, Germany); 3) 24-hour ambulatory blood pressure (ABP) monitoring.

Results: The mean supSBP and supDBP were found to be lower than OSBP and ODBP (130.9 ±14.2 vs. 136.6 ±15.5 mm Hg and 84.8 ±9.4 vs. 87.8 ±10.2 mm Hg, respectively; p < 0.000001). The correlations between ABP and supBP/OBP were moderate and strong (correlation coefficients in range 0.55-0.76). The ROC analysis revealed that mean supBP ≥ 130/80 mm Hg was more precise than OBP ≥ 140/90 mm Hg in diagnosing hypertension (AUC: 0.820 vs. 0.550; sensitivity 80.7% vs. 57.4%; specificity 83.2% vs. 52.7%; p < 0.0001) and the additive value derived mostly from its higher predictive power of identifying patients with increased night-time BP.

Conclusions: In young and middle-aged hypertensive patients the blood pressure during a 10-minute supine rest was lower than in the sitting position. The supine blood pressure ≥ 130/80 mm Hg was found to be a specific and sensitive threshold for hypertension.

Keywords: ambulatory blood pressure monitoring; body position; impedance cardiography; office blood pressure.

Figure 1

Comparison of BP (mm Hg) measured by three methods (for 530 measurements): A – mean supSBP vs. OSBP vs. daytime SBP; B – mean supDBP vs. ODBP vs. daytime DBP

Figure 2

Correlation plots: A – mean supSBP versus daytime SBP; B – mean supDBP vs. daytime DBP

Figure 3

Bland-Altman plot for mean supSBP and daytime SBP. The horizontal solid line shows the mean difference between methods and the dashed lines show the limit of agreement (±1.96 standard deviation of the difference between daytime SBP and mean supSBP)

Figure 4

Bland-Altman plot for mean supDBP and daytime DBP. The horizontal solid line shows the mean difference between methods and the dashed lines show the limit of agreement (±1.96 standard deviation of the difference between daytime DBP and mean supDBP)