Professional and Linguistic Assessments Board (PLAB) Practice Exam

What is the first test typically performed for hyperaldosteronism?

1. Serum aldosterone level

2. Renin:aldosterone ratio

3. 24-hour urine collection

4. Adrenal CT scan

The correct answer is: Renin:aldosterone ratio

The first test typically performed for hyperaldosteronism is the renin:aldosterone ratio. This test helps to assess the relative levels of renin and aldosterone in the blood. In hyperaldosteronism, particularly primary hyperaldosteronism (Conn's syndrome), aldosterone production is typically elevated while renin levels are low due to feedback inhibition. This ratio is critical for making a preliminary diagnosis of hyperaldosteronism. An abnormal ratio can lead to further testing, such as measuring serum aldosterone levels directly or conducting imaging studies to identify adrenal abnormalities. The renin:aldosterone ratio serves as a screening tool and is more informative when interpreting the results in the context of the patient's clinical presentation. Alternative options such as measuring serum aldosterone levels directly, conducting a 24-hour urine collection for aldosterone, or performing an adrenal CT scan are generally considered follow-up tests or confirmatory investigations after the initial screening with the renin:aldosterone ratio indicates potential hyperaldosteronism. These methods are more specific but are not the first step in the diagnostic process.