New Screening and Diagnostic Cut-off Points of PA Patients

Primary aldosteronism (PA) is the most common causes of secondary hypertension. The diagnostic workup for PA is composed of multiple steps and requires measurement of both plasma aldosterone and renin. In terms of assay of aldosterone, most of currently available chemiluminescence assays are based on competitive methods. What is actually detected is the sum of aldosterone and its metabolite aldosterone 3C glucuronide, which causes the value to be about 50%\~100% higher than the actual value. This study aims to establish a new ARR (aldosterone/renin ratio) cutoff point for PA screening and a new cutoff point for PA diagnosis, using a recently developed two-site sandwich chemiluminescence method (Snibe, China) for aldosterone and renin assay.

Hypertensive patients referred to hospitals for screening of PA will be included. All the participants proceed to seated saline infusion test (SIT) and captopril challenge test (CCT) for confirmation. Aldosterone and renin will be measured using chemiluminescent immunoassay on the Liaison analyzer (DiaSorin, Italy) and MAGLUMI X8 (Snibe, China), as well as liquid chromatography-tandem mass spectrometry (LC-MS/MS) platform. According to the experience of Fuwai Hospital, the following diagnosis criteria are proposed: Based on the results of currently used (DiaSorin, Italy), aldosterone \> 8.5ng/dL and renin \< 15μIU/mL after sitting saline infusion conform PA, and aldosterone ≤ 8.5ng/dL excludes PA.

The total number of cases to be enrolled in this study is planned to be 770, including at least 77 positive subjects and at least 406 negative subjects. By drawing the ROC curve, the point corresponding to the maximum value of the Youden index will be selected as the cutoff value, and the corresponding sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, etc. will be calculated.