Primary aldosteronism (PA) is the most common type of secondary hypertension, but it remains under-recognized and under-diagnosed, partially due to lack of internationally accepted standardized methodologies and standard reference material, according to a new review, “Laboratory challenges in primary aldosteronism screening and diagnosis.”
“PA is a directly treatable form of hypertension, and the correct diagnosis can make a huge difference for the patient,” review co-author Andrew Don-Wauchope MB.BCh, MD, FRCP Edin, FCPath, FRCPath, FRCPC, told CLN Stat. “Laboratorians have an important role in managing the pre-analytical handling of samples, making sure that the analytic process is meeting appropriate quality standards, and in providing helpful interpretative comments.”
The condition involves the production of aldosterone that is either independent of or out of proportion to angiotensin II (AngII) stimulation. It doesn’t respond well to sodium loading, which would usually work to suppress aldosterone secretion, plasma renin activity, angiotensin I (AngI), and AngII. Because of the risks of hypertension, researchers are interested in finding out how to best identify and treat curable forms of hypertension such as PA.
Still, PA testing is not without its challenges, which are addressed in the new review. “The pitfall with the biggest impact on clinical practice is the interpretation of the Aldosterone Renin Ratio (ARR). Each aldosterone method detects different quantities of aldosterone, and this makes the use of literature-based data difficult for practicing physicians to apply to the method they have access to,” said Don-Wauchope. “Renin has the added challenge of having two very different techniques used to provide results. Most of the data that supports the ARR is from renin activity assays.”
Many laboratories now offer direct renin mass measurements, Don-Wauchope explained, but there is no consistent relationship between activity and mass. “This makes the ARR obtained from the literature even more difficult to interpret. Laboratorians must understand the ARR for the tests that they offer to their clinicians so that they can provide appropriate interpretative information.”
There are several key things laboratorians should know about the workup for PA, according to Don-Wauchope. “Firstly, they should know what the clinician is using the tests for. In some laboratories it will be for screening for PA using the ARR, and in others, it will be used for confirming the diagnosis with adrenal vein sampling,” he suggested. “Secondly, the tests chosen should be appropriate for clinical use and should have appropriate reference interval (RI) information for both the aldosterone assay and the renin method.”
Also, “the interpretative comments should provide reference interval information for aldosterone and renin, and if both are ordered at the same time, it would be ideal to have ARR calculated and reported with a RI,” Don-Wauchope explained. “I acknowledge that not all combinations of assays have published reference intervals available for the ARR, but the onus is on us to do our best to find the correct information. Finally, laboratorians must make themselves available to clinicians to help with the interpretation of both the ARR and the adrenal vein sampling.”
Read the review online.