What BP measurement technique should be used?
Hypertension trials use standardized clinic blood measurements to assess the efficacy of treatment regimens and BP targets. Data from these trials have been used to set BP treatment guidelines. Unfortunately, in the day-to-day world of clinical practice, standardized clinic BPs are rarely obtained, as they are technically demanding and time consuming. Improper techniques of measuring BPs correlates poorly with ambulatory BPs, which is currently considered the gold standard for BP measurement. A patient undergoing ambulatory BP monitoring wears a BP cuff for 24 hours. The BP data provided by 24-hour monitoring correlate more closely than clinic BPs, both routine and standardized, to target organ damage and cardiovascular outcomes. Both the United States and the United Kingdom advocate for the use of ambulatory BP monitoring when diagnosing patients with hypertension. Unfortunately, ambulatory BP monitoring, while considered cost effective in hypertension management, still remains largely relegated to clinical trials. An acceptable surrogate for ambulatory BP monitoring is home BP monitoring. Patients performing home BP monitoring obtain BPs in their usual settings. These data provide more information about kidney and cardiovascular risk than clinic BPs. Patients should be advised to use validated monitors. Clinicians may find a list of validated monitors at the Dabl Educational website ( http://www.dableducational.org/index.html ). A minimum of 12 BP recordings, obtained over 1 week, should be used for clinical decision making.
A recent development in BP measurement technique is automated office BP monitoring. Automated office BP measurements are obtained using either a BPTru or an Omron HEM-907. BPTru does not require a period of seated rest whereas the Omron device can be programmed to measure BP only after 5 minutes of seated rest is completed. With both devices, however, medical personnel are not in the room during the measurement. Both are validated machines that are capable of measuring clinic BP while a patient is sitting quietly alone in an examination room. Because medical personnel are absent, the white coat effect (i.e., the artificially elevated BP caused by a patient’s alerting reaction in the clinical setting) is avoided.
Automated office BPs are lower than routine and standardized clinic BPs, though each measurement technique correlates poorly to ambulatory BP measurements. However, as a predictor of target organ damage, automated office BP measurements are superior, as recently demonstrated in a trial of 275 veterans with CKD. Routine clinic BPs were measured after study participants had undergone echocardiography, and automated office BPs were measured using the Omron HEM-907 after participants had rested quietly alone for 5 minutes. Three measurements, 30 seconds apart, were obtained and averaged. Both routine clinic and automated office BP measurements did not predict daytime ambulatory BPs particularly well. Routine clinic systolic BPs were, on average, 4.8 mm Hg higher than daytime ambulatory systolic BPs, though they could underestimate daytime ambulatory systolic BPs by nearly 27 mm Hg or overestimate by 36.5 mm Hg. The automated office systolic BP data were not much better. They were, on average, 7.9 mm Hg lower than daytime ambulatory systolic BPs; they could underestimate daytime ambulatory systolic BPs by 33.2 mm Hg or overestimate 17.4 mm Hg. However, as a predictor of left ventricular hypertrophy, automated office systolic BPs performed significantly better than routine clinic systolic BPs, and they were almost superior to the predictive ability of daytime ambulatory systolic BPs.
