Plasma aldosterone and renin measurements are subject to significant intra-individual variability, including variation related to posture, time of day and sodium balance. Aldosterone secretion is not constant and may be subject to diurnal variation. As such one-off testing of ARR, does not consider the salt status of the individual necessitating repetition of tests to ensure false negative or false positive test results are ruled out. The value of accumulated aldosterone in a 24-hour sample has the advantage that it does not depend on circadian variation. This pilot observational study will help establish the positivity rates of both standard plasma aldosterone renin ratio and 24-hour urine aldosterone, and the degree to which they correlate but will help establish if untargeted screening in young-onset hypertension is feasible and test the robustness of current standard guidelines for primary aldosteronism screening and case confirmation.
