• newly-diagnosed hypertension or
• possible white coat hypertension or
• need to change antihypertensive Rx or
• poor blood pressure control.

Prior to starting home BP monitoring, subjects wore an ambulatory blood pressure monitor (ABPM) for 24 hours. They were then trained in use of an automatic oscillometric home BP monitor. Subjects were asked to take 2-3 BPs in the morning and evening, 2 days/week. They were also asked to send stored BPs to their primary care physician once a week. (A few patients were scheduled to send their BPs once a month.)

For the first 3-4 months, telephone reminders were used to enhance compliance. When patients were late sending BPs, or when they sent fewer than the requested number of BPs, a study nurse telephoned to remind them of their schedule for taking and sending BPs. At the end of the reminder period, telephone reminders were discontinued.

RESULTS
During the reminder phase, monitoring compliance was high: 27 subjects (63%) sent an average of 6 or more BPs per week; 15 (35%) sent an average of 2-5/week. When telephone reminders were discontinued, compliance decreased to 51.% and 21%. Mean weekly readings dropped from 7.1 (reminder period) to 5.8 (reminders discontinued) (p<.001, paired t test.)

• Mean home BP for the first 2 weeks of monitoring was compared to the mean daytime ABP. Home BP was 3.1/3.3mmHg higher than ABP. Pearson correlation between the two was .72 systolic (p<.001) and .60 diastolic (p<.001).

The ability to diagnose white coat hypertension (WCHTN, >2 office BP >140/90, home BP <135/85) was compared. Both home and ABPM identified 25% WCHTN, with 89% agreement.

We compared the mean home BP for the first two weeks with the mean for week 25 (or the closest week with home BP data.) Weekly mean home BP fell 8/7mmHg (p<.02/<.01) after 3-6 months of monitoring.

When we divided the cohort into white coat and sustained hypertensives, the fall in BP was similar in the sustained hypertensives. The white coat patients showed a smaller change in BP.

DISCUSSION
Our data show that 6-12 home blood pressure readings a week, taken in groups of 3 in the morning and 3 in the evening on 2 different days of the week, may be sufficient to diagnose white coat hypertension. There is concern that this approach might underestimate home blood pressure, because it does not incorporate daytime blood pressures in the workplace. However, in this study the home BP in the first 2 weeks (the time period closest to the 24-hour ambulatory monitoring period) was about 3mm higher than the daytime portion of the ABPM. This difference, if confirmed, would mean that 2 weeks of home BP monitoring will yield a slightly conservative estimate of white coat hypertension.

The fall in home BP observed in this study must be interpreted with caution. There is no independent measure of BP at the final week, and there is no control group. (The next phase of this study, currently in progress, will correct both of these deficiencies.) With this caveat in mind, there is some indication that our data may represent a true fall in blood pressure. The fact that the white coat hypertensives experienced a smaller change would be predicted, since these patients did not have elevated BP at home at entry. In the next phase of this study, we will attempt to confirm the current results with a larger cohort and randomized controls.
There are several possible mechanisms to explain the fall in blood pressure:

• The repeated feedback to the patient by the home monitor of elevated BP may encourage better medication and/or lifestyle compliance.
• Regular reports of elevated BP to providers may stimulate more aggressive treatment.
• Patients, aware of inadequate BP control, may seek more aggressive treatment from providers.