Risk factors

Misdiagnosed hypertension points to need for out-of-office BP assessments


High rates of undiagnosed hypertension, ‘masked hypertension’ and inadequately treated hypertension have been found in an Australian study comparing clinic BP measurement and 24-hour ambulatory BP monitoring.

The results from a subgroup of  508 patients in the AusDiab study found that systolic but not diastolic BP was higher in clinic setting vs ambulatory measurement (mean 127/73 mmHg vs 121/73 mmHg).

There was excellent correlation between clinic measures and ABPM 24-hour measures, both day and night values, and the predicted ABPM daytime equivalent for the hypertension threshold values of 140/90mmHg were 136/90mmHg.

Of the total cohort, 43% were hypertensive based on 25% being on antihypertensive therapy and a further 17% having ABPM mean 24-h BP greater than 130/80mmHg.

Surprisingly few participants had white-coat hypertension (2.8%) but 20.7% had masked hypertension indicating 24% misdiagnosis.

Based on ABPM, 17% had untreated hypertension and 9% had treated hypertension. Only a quarter of those with hypertension were taking antihypertensive therapy.

Of those treated, 36% had not reached target BP which was an average of 50% for men and 21% for women.

“If this translates to the community at large, then clearly considerably more effort must be made to highlight the known cardiovascular risk associated with hypertension in all parts of the community including urban and rural populations ,” concluded the study authors in the Journal of Hypertension,

Lead study investigator Professor Geoff Head, Head of Neuropharmacology at the Baker Institute, Melbourne, described the findings as staggering and said they showed the need for wider use of ambulatory BP measures.

“These results clearly suggest we need to make changes in screening and treatment plans as soon as possible,” he said.

Ambulatory BP monitoring be made available under Medicare, he suggested.

“The answer is two-fold. First we have to encourage GPs to diagnose high blood pressure using the most appropriate methods and the second is to make screening cheaper for those who cannot afford it”, he said.

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