Relationship between Joint National Committee-VI classification of hypertension and ambulatory blood pressure in patients with hypertension diagnosed by casual blood pressure

Background: White-coat hypertension has been diagnosed arbitrarily based on different criteria. In 1997, the Joint National Committee-VI (JNC-VI) reported a new classification of hypertension and strongly emphasized the importance of ambulatory blood pressure (ABP) monitoring. The report pronounced normal ABP values for the first time. Hypothesis: The study's aim was to clarify the relationship between casual blood pressure (BP) and ABP of patients with essential hypertension in each stage of JNC-VI classification, and the prevalence of white-coat hypertension diagnosed by using JNC-VI normal ABP criteria. Methods: Ambulatory blood pressure was monitored noninvasively in 232 patients with essential hypertension whose casual BP was greater than or equal to 140/90 mmHg. The patients were classified according to JNC-VI classification, and their casual BP was compared with ABP. The criterion of white-coat hypertension was defined as casual BP greater than or equal to 140/90 mmHg with normal ABP according to JNC-VI criteria (< 135/85 during daytime and < 120/75 during nighttime). Results: Mean ABP increased as the stage advanced, and the differences between casual BP and ABP also increased. There were considerable overlaps in the distribution of ABP among stages. The prevalence of white-coat hypertension was 13% overall: 30% of the patients with isolated systolic hypertension, 19% of those in stage 1, 10% in stage 2, and 4% in stage 3. Conclusions: Classification of hypertension based on casual BP may not always correspond in severity to that based on ABP. Ambulatory blood pressure monitoring recommended by JNC-VI is very useful for the evaluation of hypertension to differentiate white-coat hypertension from true hypertension.