Introduction:

A new online, self-administered questionnaire called the “Sodium Calculator” (SC) was developed inMexico, designed to provide immediate feedback on their sodium intake.

Objective:

This study aimed to evaluate the reliability and concurrent criterion validity of the SC for estimating sodium intake in the Mexican population.

Materials and Methods

: A cross-sectional study was conducted in Mexico City and the State of Mexico with 353 healthy participants. Data collection included 24- hour urine samples for sodium measurement, physical measurements (height and weight), and a three-day food diary. One week later, participants completed the SC again. Statistical analysis involved the intraclass correlation coefficient (ICC), Bland-Altman plots, sensitivity (Sn), specificity (Sp), and binary logistic regression, with significance set at p < 0.05.

Results:

The SC tended to overestimate sodium intake by approximately 2524 mg compared to 24-hour urinary sodium. The ICC between SC and urine measurements was 0.18 (95% CI 0.33-0.59), and 0.46 (95% CI 0.31-0.58) for test-retest reliability. The sensitivity of the SC for detecting intake > 2300 mg was 82.87%, but specificity was low at 25.71%. The odds ratio for identifying individuals with intake > 2000 mg was 4.32 (CI = 2.49-7.48, p < 0.001).

Conclusions:

The SC showed moderate test-retest reliability. However, the low agreement with 24-hour urinary sodium excretion (UNa), prevents it from being validated as an accurate quantitative measure of daily sodium intake. Despite these limitations, the SC shows promise as a screening tool.