Abstract: Renin is a critical biomarker for diagnosing secondary hypertension such as primary aldosteronism. Renin-related laboratory tests include the measurement of plasma renin activity (PRA) and direct plasma renin concentration (PRC). These two tests differ significantly in both methodology and clinical implications, which can easily lead to confusion in clinical practice. This article elaborates on the differences between the two types of renin assay kits in terms of detection principles, influencing factors, and practical applications, reviews their current registration status, discusses issues related to regulatory evaluation, and proposes improvement suggestions.