Background: Primary aldosteronism (PA) is the most common endocrine cause of hypertension with a reported prevalence of 3 – 13% in primary care. Timely diagnosis is important, since PA carries a worse prognosis compared to blood pressure-matched essential hypertension. However, even though effective targeted treatments are available, evidence suggests that PA is substantially under-diagnosed. A recent survey of Victorian primary care clinics revealed that < 0.1% of 7000+ hypertensive patients had a diagnosis of PA. This study is the first in Australia to establish the prevalence of PA in primary care populations.
Methods: Twenty primary care clinics across rural and urban Victoria were invited to screen patients with newly diagnosed, untreated hypertension, for PA by measuring their aldosterone-to-renin ratio (ARR). Those with ARR > 70 pmol/mU underwent confirmatory testing with a recumbent saline infusion test. Plasma aldosterone concentration (PAC) >140 pmol/L after the infusion of 2L normal saline confirmed the diagnosis.
Results: Of 156 patients screened, 46 had an ARR > 70. Of the 27 undertaking the saline infusion test, 23 had PAC > 140 pmol/L post saline infusion, leading to a prevalence estimate of 25%. If the most stringent cut-off for post-saline PAC is used (> 280 pmol/L), 6 patients would have PA, leading to a prevalence estimate of 7%. Baseline characteristics, in particular, age, blood pressure, and potassium levels did not discriminate between those with and without PA.
Conclusions: PA is under-diagnosed in Australian primary care, and screening has identified a prevalence of up to 25% amongst patients with newly diagnosed, treatment-naïve hypertension. Whilst the prevalence is highly dependent on the diagnostic criteria, it is much higher than currently observed. Increased awareness and access to a streamlined care pathway are needed to improve the diagnostic rate of this potentially curable cause of hypertension.