Estimating sodium intake from spot urine samples at population level: a validation and application study in French adults

• Published in: British journal of nutrition 2019-07, Vol.122 (2), p.186-194
• Main Authors: Emeville, Elise, Lassale, Camille, Castetbon, Katia, Deschamps, Valérie, Salanave, Benoît, Vernay, Michel, Guergour, Dorra, Faure, Patrice, Hercberg, Serge, Galan, Pilar, Kesse-Guyot, Emmanuelle, Verdot, Charlotte
• Format: Article
• Language: English
• Subjects: Adult; Adults; Aged; Blood pressure; Calibration; Correlation analysis; Correlation coefficient; Correlation coefficients; Diet; Diet Records; Dietary Surveys and Nutritional Epidemiology; Excretion; False Negative Reactions; Fasting; Female; France; Health surveillance; Human health and pathology; Humans; Life Sciences; Male; Mathematical analysis; Men; Mental Recall; Methods; Middle Aged; Nutrition research; Nutrition Surveys; Objectives; Population; Potassium; Public health; Salt; Sample size; Sodium; Sodium - urine; Sodium, Dietary - administration & dosage; Time Factors; Urine; Urine Specimen Collection - methods; Validation studies
• ISSN: 0007-1145; 1475-2662
• DOI: 10.1017/S0007114519000886

The aim of this study was to assess the validity of the predictive INTERSALT equation using spot urine samples to estimate 24-h urinary Na (24-hUNa) excretion and daily Na intake among the French adult population. Among 193 French adults (‘validation sample’), we assessed the validity by comparing predicted 24-hUNa excretion from spot urine and measured 24-hUNa excretion from 24-h urine collections. Spearman correlation coefficients and Bland–Altman plots were used and we calculated calibration coefficients. In a nationally representative sample of 1720 French adults (‘application sample’), the calibrated predictive equation was then applied to the spot urine Na values to estimate 24-hUNa excretion and daily Na intake. In that sample, predicted Na intake was compared with that estimated from 24-h dietary recalls. Results were adjusted and corrected using calibration coefficients. In the validation sample, the measured 24-hUNa excretion was on average 14 % higher than the predicted 24-hUNa (+13 % for men and +16 % for women). Correlation between measured and predicted 24-hUNa excretion was moderate (Spearman r 0·42), and the Bland–Altman plots showed underestimation at lower excretion level and overestimation at higher level. In the application study, estimated daily salt intake was 8·0 g/d using dietary recalls, 8·1 g/d using predicted INTERSALT equation and 9·3 g/d after applying calibration coefficients calculated in the validation study. Despite overall underestimation of 24-hUNa excretion by spot urinary Na, the use of predictive INTERSALT equation remains an acceptable alternative in monitoring global Na intake/excreted in the French population but its use is not advised at the individual level.