Primary aldosteronism: A collaborative approach for diagnosis in hypertensive patients (NSW)

Why screen for primary aldosteronism

PA is the most common secondary hypertension. Among the hypertensive patients in primary care, 5-10% have the condition.1 It has been demonstrated that PA gives rise to more severe end organ damage in comparison to primary hypertension: stroke, myocardial infarction, atrial fibrillation and death from cardiovascular causes.2 Once diagnosed, specific surgical intervention or medical treatment can lessen the damage and may even cure the hypertension.2 It is therefore beneficial to diagnose and control the condition as early as possible.

Whom to screen

Patients with hypertension which is difficult to control or associated with one or more of the following conditions should be screened for PA:

• Hypokalaemia
• Adrenal incidentaloma
• Sleep apnoea
• Family history of hypertension or cerebrovascular accident occurring at a young age
• First-degree relatives with PA

How to diagnose

After appropriate preparations, an early morning blood specimen taken after at least two hours in the ambulatory position is measured for renin and aldosterone to derive an Aldosterone/Renin Ratio (ARR). A high ARR signifies a positive screening result.1,3,4

Why the screening test is underutilised

Given the high prevalence, the more severe consequences and the potentially curable nature of the condition, it is unsatisfactory that only an extremely low proportion of hypertensive patients in general practice are screened for PA.1 This gap signifies that there are some obstacles in the process. Awareness of the condition is one. Fortunately, within our community, numerous excellent efforts have been made to raise awareness.1,3,4 Secondly, the apparently “simple” screening test can be difficult. Laboratories use different renin and aldosterone assays, and the numerical cut-off ARR values are not the same and can be confusing.

Most importantly, it is widely known that the commonly used antihypertensive drugs interfere with the diagnostic tests in different directions and magnitudes. Whilst sustained-release verapamil, prazosin, moxonidine and hydralazine have minimal effects on the screening test, how to modify antihypertensive drug treatment to prepare a patient for the screening test can be daunting. Some researchers have tried to simplify this step by minimising or even eliminating drug changes.2,3,5 Interpretation of the results, of course, need to take into account the possible effects of the remaining drugs in use.

Practitioner and pathologist collaboration for testing

A collaborative approach can overcome PA screening hurdles. The primary and most important role of a general practitioner in this process is to identify patients indicated for the screening test. Once identified, a pathologist can be engaged to recommend steps to optimise patient preparations. The pathologist can advise on correction of potassium status, other patient preparations for specimen collection, modification of antihypertensive treatment if required and interpretation of the screening test result. For patients with a positive screening result, referral to an endocrinologist or a hypertension specialist should be made to confirm the diagnosis and determine the subtype. With this collaborative approach, more hypertensive patients can benefit from an earlier detection of the condition.

Special note: This short article is meant to be a concise summary of PA. For comprehensive reviews, several excellent local publications are available.1,2,4

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