The utility of home blood pressure load in predicting average self-measured blood pressure.

ABSTRACT

OBJECTIVES: Average values for self-measured blood pressure (SMBP) more accurately reflect a patient's risk of cardiovascular disease than do office measurements. Oftentimes, however, patients provide lists of individual home blood pressure (BP) measurements, and average values cannot be computed within the time constraints of a clinic visit. In contrast, the home BP load - defined as the proportion of BP values greater than a partition value (e.g., 130 mmHg) - can be easily calculated. We examined the utility of the BP load in predicting the mean SMBP and confirming elevated SMBP. METHODS: Four hundred twenty untreated adults at least 30 years of age acquired SMBP data twice in the morning and twice in the evening over 10 days. The 'true' SMBP was defined as the mean of these 40 determinations. RESULTS: Using all 10 days of BP data and a systolic BP threshold of 130 mmHg, the average SMBP associated with a home BP load of 0.50 was 130 mmHg, with a 95% prediction interval of 126-133 mmHg. True systolic SMBP was approximately 6 mmHg lower and higher at home BP loads of 0.25 and 0.75, respectively. There was a 90% probability that the true systolic SMBP was greater than 130 mmHg if the systolic home BP load was at least 0.60. Corresponding values for 3 days and 1 day of SMBP were at least 0.68 and at least 0.84, respectively. CONCLUSION: Our analysis demonstrates that the home BP load can be used to estimate the average BP acquired on home monitoring and confirm elevated SMBP.