Ayman and Goldshine first reported comparisons between blood pressures measured in the clinic and at home in 1940. In this report, blood pressures of patients with essential hypertension were obtained through an extensive assessment in the clinic as well as from home blood pressures measured twice daily for several weeks.
Thirty percent of the hypertensive patients exhibited home-derived measures of SBP that were more than 40 mm Hg lower than the clinic-derived measures, and 24 percent of the patients exhibited home-derived measures of DBP that were more than 20 mm Hg lower than clinic-derived DBPs. Across most patients, home-derived measures of blood pressure were substantially lower than clinic-derived measures. Research since that time has underscored the replicability of these findings (Battig et al., 1989; Kleinert et al., 1984; Laughlin, Sherrard, and Fisher, 1980).
In fact, this finding is so robust that some hypertension specialists have suggested establishing a lower blood pressure criterion for considering a diagnosis of essential hypertension (Thijs et al., 1998). Based upon a meta-analysis of 17 studies comparing home and clinic measures of blood pressure in well over 5400 persons, these authors reported that a clinic-derived SBP of 140 mm Hg corresponded to a home-derived SBP of 125 mm Hg, and that a clinic-derived DBP of 90 mm Hg corresponded to a home-derived DBP of 79 mm Hg.
In a second analysis of pooled home blood pressures of over 4500 patients from an international database, Thijs et al. (1999) found that at least 25 percent of hypertensive patients using clinic criteria had self-recorded blood pressures less than 135/85 mm Hg; this finding was particularly evident among patients who underwent fewer than three blood pressure measurements in defining their clinic SBP and DBP. Based upon the results of these two studies, Thijs et al. (1999) suggested that home blood pressure recordings that exceed 135/85 mm Hg should be considered hypertensive.
This suggestion was endorsed by the task force comprised of international experts in blood pressure assessment at the Leuven Consensus Conference on Ambulatory Blood Pressure Monitoring in 1999 (White et al., 1999).
Although office blood pressures are typically higher than those recorded through home self-monitoring, this difference becomes much smaller among persons accustomed to the clinic environment (Welin, Svardsudd, and Tibblin, 1982). For example, Padfield et al. (1987) demonstrated a significant relation between home blood pressures and blood pressure measures obtained on the third clinic visit, a finding which was not apparent during the first two clinic visits.
Therefore, if a slightly lower criterion for home blood pressure monitoring is adopted and the frequency of clinic visits increased, home monitoring can be a valuable tool for obtaining accurate assessments to evaluate and monitor treatment progress.