Only 2% of patients admitted to hospital for stroke or transient ischemic attack undergo primary aldosteronism testing, despite almost one-third meeting the guideline criteria for investigation, an Australian study has shown.
The retrospective cohort study involved patients (mean age 74, 42% female) admitted with stroke or transient ischemic attack (ischemic stroke 68.9%; haemorrhagic stroke 5.6%; and TIA 25.6%) at two tertiary hospitals in Victoria.
About three quarters of the cohort had a history of hypertension.
Of 400 patients hospitalised between 2019 and 2020, 30% (n=120) had a clinical indication for primary aldosteronism testing, but only 2% (n=8) were tested.
The most common reason for primary aldosteronism testing – with indications based on Endocrine Society guidelines – was resistant hypertension (BP ≥140/90 mm Hg despite treatment with three or more antihypertensive agents).
In the subgroup of patients with concurrent hypertension, an even bigger proportion (32.9%) had indications for testing, but only 5.8% (n=7) were tested.
Patients with an indication for primary aldosteronism testing did not differ from those without an indication for testing in regards to age, sex, stroke type, number of previous strokes or TIAs and most comorbidities. However, those with an indication for primary aldosteronism testing had a higher heart failure rate (15.8% versus 3.3%) and a lower estimated glomerular filtration rate (64 versus 74).
Lead author Dr Josephine McCarthy is a PhD student investigating endocrine hypertension at Hudson Institute of Medical Research and an endocrinologist at Monash Health.
These additional features should prompt consideration of testing, said the research team, led by Monash University, the Centre for Endocrinology and Metabolism at Hudson Institute of Medical Research, and Monash Health in Melbourne.
While lack of data limited the researchers’ ability to assess the prevalence of primary aldosteronism, they said their findings still highlighted a missed opportunity to identify a treatable cause of hypertension and a highly modifiable cardiovascular risk factor.
“Our findings align with low testing rates reported in other healthcare settings,” the researchers said in their brief report for the journal Stroke [link here].
“In Australia, primary aldosteronism testing rates in diabetes clinics, nephrology clinics, and emergency settings were also low at 2% to 5%, despite 22% to 43% of patients having indications for testing.
“In the present study, only 2% of patients overall were tested for primary aldosteronism, reflecting persistent under-recognition even in high-risk populations.”
They said the lack of testing might be due to low clinician awareness of primary aldosteronism and perceived difficulties in interpreting aldosterone-to-renin ratio in patients taking interfering medications who might have false negative results.
The researchers pointed to Endocrine Society recommendations that stated aldosterone-to-renin ratio (ARR) should be performed and interpreted in light of interfering medications if these medications could not be safely withdrawn.
An unrelated analysis showed an ARR threshold of 18.9 pmol/ mU – much lower than the standard cutoff of 70 pmol/mU – was 96% sensitive and 61% specific for primary aldosteronism in the context of interfering medications, they added.
“Stroke physicians, who often manage hypertension, are uniquely positioned to identify primary aldosteronism, thus enabling improved BP control with reduced risk of stroke recurrence,” the researchers said.
“Prospective research is needed to determine the true prevalence of primary aldosteronism in this high-risk population, establish the optimal time to screen, and refine ARR interpretation in the context of interfering medications.”