[Nomogram for the relation between plasma renin activity and fasting urinary sodium creatinine ratio (author's...

Based on repeat measurements in 11 male and 12 female normal subjects, aged 20 to 35 years, on normal, low and high sodium intake a nomogram for the relation between fasting urinary sodium creatinine ratio and plasma renin activity (PRA) is presented. The use of fasting urinary sodium creatinine ratio as index of sodium intake and hydration of the subject results in a better prediction of PRA as compared with 24-hour urinary sodium excretion. Although fasting urinary sodium creatinine ratio in normal subjects on a normal sodium intake varies between 0.2 and 1.6, a uniform increase of basal PRA is found only at a ratio of below 0.3. A ratio greater than 0.5 excludes any stimulation of PRA by low sodium intake and (or) dehydration of the subject. The shape of the nomogram should make it applicable independent of the method used for PRA assay, as soon as the variation of PRA in normal subjects with a urinary sodium creatinine ratio above 0.5 is established.