Applying recovery biomarkers to calibrate self-report measures of sodium and potassium in the Hispanic Community Health Study/Study of Latinos

Measurement error in assessment of sodium and potassium intake obscures associations with health outcomes. The level of this error in a diverse US Hispanic/Latino population is unknown. We investigated the measurement error in self-reported dietary intake of sodium and potassium and examined differences by background (Central American, Cuban, Dominican, Mexican, Puerto Rican and South American). In 2010–2012, we studied 447 participants aged 18–74 years from four communities (Miami, Bronx, Chicago and San Diego), obtaining objective 24-h urinary sodium and potassium excretion measures. Self-report was captured from two interviewer-administered 24-h dietary recalls. Twenty percent of the sample repeated the study. We examined bias in self-reported sodium and potassium from diet and the association of mismeasurement with participant characteristics. Linear regression relating self-report with objective measures was used to develop calibration equations. Self-report underestimated sodium intake by 19.8% and 20.8% and potassium intake by 1.3% and 4.6% in men and women, respectively. Sodium intake underestimation varied by Hispanic/Latino background (P<0.05) and was associated with higher body mass index (BMI). Potassium intake underestimation was associated with higher BMI, lower restaurant score (indicating lower consumption of foods prepared away from home and/or eaten outside the home) and supplement use. The R2 was 19.7% and 25.0% for the sodium and potassium calibration models, respectively, increasing to 59.5 and 61.7% after adjusting for within-person variability in each biomarker. These calibration equations, corrected for subject-specific reporting error, have the potential to reduce bias in diet–disease associations within this largest cohort of Hispanics in the United States.