Blood pressure assessment in haemodialysis patients: Comparison between pre-dialysis blood pressure and ambulatory blood pressure measurement

Aim: Hypertension is common in haemodialysis (HD) patients. Determining the most appropriate method of blood pressure (BP) measurement, representative of target organ damage, is still an issue. BP variations between pre‐ and post‐HD treatment, or between on‐dialysis day and off‐dialysis day, are common. The aim of this study was to examine the possible differences between pre‐HD office BP (OBP) levels, inter‐HD (iHD) or HD day 24 h ambulatory BP measurement (ABPM) with 48 h ABPM, where the latter was considered the gold standard. Methods: 163 HD patients were studied. BP was monitored consecutively for 48 h with a Takeda TM2421 device, then sub‐analysed into two periods of 24 h: HD and iHD day. An average of 12 sessions pre‐HD OBP measurements was determined. Results: OBP significantly overestimates systolic (SBP) and diastolic BP (DBP) when compared with 48 h ABPM. SBP and DBP are significantly higher on iHD day than on HD day: 141.2 ± 20.8 versus 137.9 ± 20.9, and 77.1 ± 11.1 versus 76.1 ± 10.9 (P < 0.01). No differences of SBP night/day ratio were reported between 48 h ABPM and iHD 24 h ABPM or HD 24 h ABPM. The highest correlations were reported between 48 h SBP/DBP with iHD or HD 24 h ABPM (r² = 0.95, P < 0.001), while the lowest between 48 h SBP/DBP and OBP (r² = 0.40, P < 0.01, r² = 0.12, P < 0.01). The narrowest limits of agreement using the Bland and Altman test were reported between 48 h SBP or DBP and 24 h iHD or HD day ABPM. Considering 48 h ABPM, 80.5% of patients had BP higher than the norm, compared with 61.7% of patients in the case of OBP (χ² = 13.28, P < 0.001). The sensibility for detecting hypertension for iHD day 24 h ABPM was 98.4%, with specificity of 90%. The sensibility of 24 h HD day ABPM was 90.3%, with specificity 96.6%. In the case of OBP, sensibility and specificity were considerably lower, that is, 72.6% and 83.3% respectively. Conclusion: Significant differences are shown between OBP and 48 h ABPM in the recognition of a hypertensive state. OBP measurement has a lower sensibility and specificity than 24 h ABPM, which remains a valid alternative approach to 48 h ABPM in HD patients. Errors of OBP estimation should be taken into account, with possible negative impact on treatment strategies and epidemiology studies.