Abstract P328: Estimating the Population Distribution of Usual 24-Hour Sodium Excretion From Timed-Spot Urine Specimens Among Adults 18-39 Years
Introduction: National efforts toward reducing population sodium intake necessitate developing a feasible and valid monitoring method, especially for the distribution tails given about 90% of the US population consumes more sodium than recommended.
Objective: We developed and tested the validity of a statistical approach using one or two timed-spot urines to estimate population distribution of usual 24-hour sodium excretion.
Methods: A convenience sample of 407 adults, 18-39 years of age, (54% female, 48% black) collected urine for a 24-hour period, placing each void in a separate container. Of these, 133 repeated the procedure 4-11 days later. Four timed-spot specimens (morning, afternoon, evening, and overnight) were selected from each 24-hour collection. We developed gender-specific equations using Fuller’s error-in-the-equation measurement error model to calibrate total sodium excreted in each of the one-spot (e.g., morning) and combined two-spot (e.g., morning + afternoon) urines to 24-hour sodium excretion. The calibrated sodium excretions were used to estimate the population distribution of usual 24-hour sodium excretion. Participants were then randomly assigned to modeling (n=160) or validation (n=247) groups to examine the bias in estimated population percentiles.
Results: Median bias in predicting the 5th, 25th, 50th, 75th, and 95th population percentiles of usual 24-hour sodium excretion with one-spot urine ranged from -367 to 284 mg (-7.7 to 12.2% of the observed usual excretions) for men and -604 to 486 mg (-14.6 to 23.7%) for women, and with two-spot urines from -338 to 263 mg (-6.9 to 10.4%) and -166 to 153 mg (-4.1 to 8.1%), respectively. Four of the six two-spot urine combinations produced no significant bias in predicting selected percentiles.
Conclusions: Our approach to estimate the population distribution of usual 24-hour sodium excretion using calibrated spot urine sodium accounted for day-to-day variation and covariance between measurement errors, and produced percentile estimates with relatively low biases across low to high sodium levels. This may provide a low-burden, low-cost alternative to 24-hour collections in monitoring population sodium intake among healthy young adults and merits further investigation in other population subgroups.
Author Disclosures: C. Wang: None. A.L. Carriquiry: None. T. Chen: None. C.M. Loria: None. C.M. Pfeiffer: None. K. Liu: None. C.T. Sempos: None. C.G. Perrine: None. M.E. Cogswell: None.
- © 2015 by American Heart Association, Inc.