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Primary aldosteronism (PA) has been underrecognized and probably undertreated in Canada, new research suggests.

In a cohort study of 1.1 million adults with hypertension, a paltry 0.7% were screened for PA -- one of the most common causes of secondary hypertension -- according to Alexander Leung, MD, MPH, of the University of Calgary in Canada, and colleagues.

As they reported in the study online in , of the approximately 8,000 individuals screened for PA, about 21% tested positive for possible PA, defined as an elevated aldosterone-to-renin ratio (ARR), but fewer than half of patients who tested positive for a unilateral and bilateral form of PA actually received treatment.

All in all, this equated to less than 1% of patients suspected to have PA ever receiving a formal diagnosis and subsequent treatment.

Of the few patients who did receive disease-specific treatment, the vast majority received medical therapy, such as a potassium-sparing diuretic, while only about 16% underwent adrenalectomy.

And those who received disease-targeted treatment were most likely to be under the care of an endocrinologist rather than other clinicians. Not surprisingly, endocrinologists more frequently referred patients for adrenal vein sampling and patients were twice as likely to undergo an adrenalectomy when an endocrinologist did the workup.

" recommend thorough consideration and investigation of PA in patients who require three or more drugs to control their blood pressure, as well as those with hypokalemia or adrenal nodules," Leung and co-authors pointed out, adding that based on these criteria, roughly with hypertension should be screened for PA.

"A system-level approach to simple work-up and treatment may be effective in closing care gaps and improving clinical outcomes for patients with PA. With the declining rates of blood pressure control in the U.S. and Canada, proper workup and treatment of secondary causes of hypertension, especially PA, has become more relevant than ever," the researchers concluded.

The retrospective, population-based study looked at data on adult Canadian patients appearing in a government healthcare database.

Hypertension was identified through an ICD-10 code during a hospitalization or by two physician claims with ICD-9 codes within 2 years of each other. From there, some patients who were further screened for PA had ARR testing, with a ratio above 20 ng/dL (550 pmol/L) considered an "abnormally high" level.

Among those that had a positive screen result, about 57% received CT or MRI, while only about 15% underwent adrenal vein sampling.

Factors tied to higher PA screening rates included hypokalemia, being on three or more drugs for hypertension, and being younger than 40. Not surprisingly, patients with hypokalemia who were also on three or more hypertension medications had the highest rates of positive ARR test results.

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