Adrenal venous sampling for primary aldosteronism: laboratory medicine best practice

Primary aldosteronism (PA) is the most common form of secondary hypertension and is critical to identify because when caused by an aldosterone-producing adenoma (APA) or another unilateral form, it is potentially curable, and even when caused by bilateral disease, antihypertensives more specific to PA treatment can be employed (ie, aldosterone antagonists). Identification of unilateral forms is not generally accomplished with imaging because APAs may be small and elude detection, and coincidental identification of a non-functioning incidentaloma contralateral to an APA may lead to removal of an incorrect gland. For this reason, the method of choice for identifying unilateral forms of PA is selective adrenal venous sampling (AVS) followed by aldosterone and cortisol analysis on collected samples. This procedure is technically difficult from a radiological standpoint and, from the laboratory perspective, is fraught with opportunities for preanalytical, analytical and postanalytical error. We review the process of AVS collection, analysis and reporting. Suggestions are made for patient preparation, specimen labelling practices and nomenclature, analytical dilution protocols, which numerical results to report, and the necessary subsequent calculations. We also identify and explain frequent sources of confusion in the aldosterone and cortisol results and provide an example of tabular reporting to facilitate interpretation and communication between laboratorian, radiologist and clinician.