DISCORDANCE OF MERCURY SPHYGMOMANOMETER AND AMBULATORY BLOOD-PRESSUREMEASUREMENTS FOR THE DETECTION OF UNTREATED HYPERTENSION IN A POPULATION STUDY

To evaluate the extent to which ambulatory blood pressure (ABP) measur ements could redefine the prevalence of untreated hypertension in the general population, we studied a randomly selected subgroup of the Nat ional Heart Foundation of Australia's Risk Factor Prevalence Study 198 9. Subjects taking blood pressure (BP) lowering medications were exclu ded, leaving 66 patients with 24h ABP recordings for analysis. Mean aw ake ABPs were generally lower than survey BPs and diminished with redu ced activity (away from work and during sleep). The correlation of sur vey BP and daytime ABP (10.00-20.00 h) classification of untreated hyp ertension was moderate (Cohen's correlation coefficient 0.490. 56). Un treated hypertension was identified in 20 subjects by the mercury sphy gmomanometer technique (BP greater-than-or-equal-to 150/90 mmHg). Six (30%) of those subjects had a mean ABP < 135/85 mmHg suggesting 'normo tension' on ambulatory criteria. Conversely, 19 subjects had a mean AB P of greater-than-or-equal-to 135/85 mmHg, five (26%) of whom had 'nor mal' survey BPs. We conclude that ambulatory and mercury sphygmomanome ter methods of BP measurement in this population study defined a simil ar prevalence of untreated hypertension but were discordant for a subs tantial percentage of individuals. The prognostic significance of ABP levels and any discordance with survey or office mercury sphygmomanome ter BP readings will remain uncertain until prospective studies using both forms of measurement are completed.