Predicting 24-hour urinary sodium excretion in Afro-Caribbean Barbadians by comparing urine sodium excretion over different durations versus spot collection.

Abstract

AIM Urinary sodium excretion is used as an assessment tool for salt intake and salt handling. Even though cumbersome, the most reliable and readily used method in clinical and epidemiological studies is the 24-hour urine collection. This study investigates other appropriate means ofpredicting 24-hour urinary sodium excretion in a sample of Afro-Caribbeans in Barbados by assessing the correlation of actual and estimated urinary sodium excretion between a 24-hour urine collection sample, 12-hour (AM and PM), and spot (AM and PM) urine collections. METHOD A convenient sample of 30 healthy participants of Afro-Caribbean origin between the ages of 21 and 55 years was recruited for the study. The 24-hour urine samples and anthropometric data were collected as documented in the study's standard clinical procedure. A 24-hour urine sample was collected as two separate 12-hour AM and PM samples. In addition, two spot samples (AM and PM) were taken during each 12-hour sample collection period. Analysis of the urinary sodium and creatinine was done with a Roche/Hitachi Modular System (Roche Diagnostics, IN, USA). SPSS version 19 was used to analyse the data to make inferences. RESULTS Thirty Afro-Caribbean subjects participated in this study: 16 females and 14 males. The average age and body mass index (BMI) were 38 +/- 17 years and 25.32 +/- 5.98 kg/m2, respectively. The greatest correlation of the estimated 24-hour sodium excretion to the measured 24-hour sodium excretion was observed in the 12-hour PM sample (Pearson's correlation, r = 0.786, p < 0.001) followed by the 12-hour AM sample (Pearson's correlation, r = 0.774, p < 0.001). The PM spot sample showed a weaker, but still statistically significant correlation to the 24-hour timed sample (Pearson 's correlation, r = 0.404, p < 0.045). The AM spot sample showed a very weak and insignificant correlation (Pearson 's correlation, r = 0.05, p = 0.807) to the 24-hour timed sample. Similarly to the whole sample, the gender analysis demonstrated that estimated 24-hour sodium excretion in the female's 12-hour PM sample had the greatest correlation (r = 0.819, p < 0.001) to the measured 24-hour sodium excretion, followed by the 12-hour AM (r = 0.793, p = 0.001) and the PM spot samples (r = 0.741, p = 0.02). The correlation between variables is weaker in males compared to the females. CONCLUSION Overall, this study shows a clear correlation between the estimated 24-hour sodium excretion from the 12-hour timed PM sample and the measured 24-hour sodium excretion. Such findings support the thought of using other alternatives to determine sodium excretion, in view of replacing the cumbersome 24-hour urinary collection with a smaller timed sample. Nonetheless, a more robust and randomized population sample as well as a method to correct for high creatinine variability is required to further enhance the significance of the obtained results.