How should patients monitor their own blood pressure: a systematic review

Conference: 
SAPC ASM 2015 - Oxford - Evidence and innovation in primary care
Talk Code: 
EP2A.2

The problem

Self-monitoring of blood pressure (SMBP) has the potential to better estimate underlying blood pressure (BP), is increasingly popular with patients, and is endorsed in hypertension guidelines worldwide. However, there is little agreement as to the optimal self-monitoring schedule. We systematically reviewed the literature regarding the optimum schedule for SMBP in terms of both prediction of future cardiovascular events and the relationship between the number of readings taken and true underlying BP, considering the number, timing and frequency of self-monitoring.

The approach

Six electronic databases were searched from November 2009 (updating a NICE systematic review) to September 2013. Data were extracted independently by two reviewers from each included paper on study/ population characteristics, methodological quality, self-monitoring regime details, and outcomes, including any resulting SMBP schedule recommendations. For prognostic studies reporting hazard ratios (HR), the adjusted HRs per 1mmHg increase in BP were summarised along with the associated outcome. For reliability/ reproducibility studies, correlations reported between SMBP and ambulatory BP measurement (ABPM) were summarised.

Findings

From 2,530 unique papers identified, 10 met the inclusion criteria. A further 12 studies were included from the NICE review.Ten studies identified an optimal number of days to monitor per week (mode 3; mean 4.10 [SD1.7]; range 3-7); nine an ideal number of measurements to be taken each day (mode 4; mean 3.4 [SD1.5]; range 1-6); eleven the number of readings to take on each occasion (mode 2; mean 2.2 [SD0.8]; range 1-3). Seven recommended a total number of measurements to be taken per week (mode 12; mean 15.9 [SD9.6]; range 6-30), some suggesting how many measurements should be discarded (mode 0 or 4; mean 5.2 [SD7.4]; range 0-18) and how many used (mode 8; mean 13.0 [SD7.6], range 5-28). Nine papers advocated taking readings in both the morning and evening having assessed what time of day to take measurements. Only one paper assessed the best particular time interval (one minute) to rest between measures. Heterogeneity and concerns over methodological quality (notably use of unvalidated monitors and selection bias) rendered interpretation problematic.In prognostic studies, 72-83% of the theoretical maximum predictive value (asymptotic maximum HR) was reached by 3 days and 85-92% by seven days. Similar results were obtained for correlation coefficients for reliability/ reproducibility studies.

Consequences

Though there was significant variation in the optimal monitoring schedule identified in different studies, the most frequently recommended schedule elements comprised using readings from at least 3 days, excluding values from the 1st day, with duplicate morning and evening measurements (i.e. 4 a day, 12 in total). Clinicians recommending BP self-monitoring to patients should advise that having three days of useable values is a minimum requirement.

Credits

  • James Hodgkinson, School of Psychology, University of Central Lancashire, Preston, UK
  • Sabrina Grant, School of Psychology, University of Central Lancashire, Preston, UK
  • Emma Bray, Department of Primary Care Health Sciences, University of Oxford, Oxford, UK
  • Sarah Stevens, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK
  • Una Martin
  • Richard Stevens, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK
  • Rafael Perera-Salazar, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK
  • Richard McManus, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK