Reply to: On poor agreement between dialysis unit and ambulatory blood pressures.

Abstract

We do appreciate the interest from Dr Fülöp and Dr Zsom regarding our published work. They raised a concern about the correlation between dialysis unit blood pressure (BP) measurements and ambulatory BP values. To address this issue, we carried out an analysis and found that in our study both postdialysis (P<.001) and predialysis (P<.001) systolic BPs were independently correlated with ambulatory systolic BP. The conclusion was similar for diastolic BP (P<.001 for postdialysis diastolic BP, P=.025 for predialysis diastolic BP). Although disparities exist in the results between Dr Fülöp and Dr Zsom's and ours, both studies had a similar conclusion that postdialysis BP has a more pronounced correlation with ambulatory BP. However, caution should be taken when interpreting such data because of the disparities in many factors such as the method for obtaining dialysis unit BP and the size of the population. Hence, conclusions should be validated by additional well-designed studies. In fact, in a representative study by Agarwal and colleagues,1 the authors concluded that intradialytic BPs should also be taken into consideration together with predialysis and postdialysis BPs for diagnosing hypertension. While predialysis and/or postdialysis BPs are tightly correlated with ambulatory BP, it is worthy to note that the association does not equal agreement. There is no doubt that the agreement between dialysis unit BP and ambulatory BP is poor.2 Given the inconvenience and cost of ambulatory BP monitoring, home BP has been shown to be a reliable and feasible option for BP management in dialysis patients.3