Martinez-Aguayo AG, Campino C, Rodriguez-Fernandez M, et al. - Researchers explored the links among the plasma renin concentration (PRC), plasma aldosterone and urinary sodium (Na)/potassium (K) ratio, as well as combined these variables into a nomogram for estimating the expected vs observed aldosterone concentration. Healthy normotensive children (n = 40, 5–8 years old, 57.5% girls) who were born at term and were adequate for their gestational age were examined. Blood samples were obtained after overnight fasting to measure PRC and plasma aldosterone, and a simultaneously obtained urinary spot sample was analyzed to calculate the Na/K ratio. The development of a nomogram to predict aldosterone levels was enabled by the strong correlation between the urinary Na/K ratio and plasma renin and aldosterone levels. The identified significant independent predictors of plasma aldosterone were PRC and urinary Na/K ratio. The correlation between the detected plasma aldosterone and the expected plasma aldosterone, as obtained from the nomogram, was found to be r = 0.88, P < 0.001. Overall, findings are suggestive of the likely usefulness of this approach for assessing the renin–angiotensin–aldosterone system (RAAS) among pediatric patients having hypertension and RAAS dysfunction.