Formula to detect high sodium excretion from spot urine in chronic kidney disease patients

Abstract Introduction: Excessive sodium intake is related to adverse renal and cardiovascular outcomes in patients with chronic kidney disease (CKD) and assessment of sodium intake is complex and not evaluated very often in clinical practice. Objective: To develop a new formula to estimate 24h sodium excretion from urine sample (second void) of patients with CKD. Methods: We included 51 participants with CKD who provided 24-hour urine collection and a sample of the second urine of the day to determine the sodium excretion. A formula to estimate the 24-hour sodium excretion was developed from a multivariate regression equation coefficients. The accuracy of the formula was tested by calculating the P30 (proportion of estimates within 30% of measured sodium exection) and the ability of the formula to discriminate sodium intake higher than 3.6 g/day was evaluated by ROC curve. Results: Correlation test between measured and estimated sodium was significant (r = 0.57; p