Reproducibility and Treatment Effect on Office and Ambulatory Pressure Relation.

Background: In the absence of outcome-based ambulatory blood pressure (BP) data hypertension guidelines provide 24-hour mean BP values corresponding to trial-validated office BP values. Data are shown for untreated and treated patients together, but whether corresponding ambulatory values are similar in untreated and treated hypertensives and reproducible at yearly measurements during treatment is undefined.
Methods: In 2397 patients of the ELSA (European Lacidipine Study on Atherosclerosis) and PHYLLIS (Plaque Hypertension Lipid-Lowering Italian Study) trials, we calculated the office and 24-hour BP relationship according to the linear regression model, with office systolic BP as the independent variable, at baseline and yearly during a 3-year treatment. Twenty-four hour BP values corresponding to clinically important office BP values (hypertension grades and treatment thresholds and targets) were calculated and compared with those provided by guidelines.
Results: Office/24-hour systolic BP or diastolic BP always exhibited a significant linear relationship, with, however, limited Pearson correlation coefficients (never >0.44).The slopes of the relationship were superimposable between different years of treatment but always significantly less steep than the slope seen in untreated individuals. Compared with the guideline-provided corresponding values, 24-hour BP showed qualitative and quantitative differences; for example, it was considerably lower and higher than the guideline-corresponding values when office BP was in the high hypertension and low treatment target ranges, respectively.
Conclusions: In treated patients with hypertension the slope of the office/24-hour BP linear regression is reproducible over time. However, the slopes are steeper in untreated individuals, indicating that information on ambulatory BP values corresponding to office BP values can be more accurate if separately estimated in these 2 conditions.