Reliability and validity of a low cost, pocket-sized and battery operated sodium analyzer in measuring urinary sodium...

The 24-h urine collection technique is the reference method for assessing sodium intake. Frequent assessments of urinary sodium excretion improve patients' motivation in adhering to sodium-restricted diets. No portable, inexpensive, user-friendly and reliable sodium analyzers are available on the market. Allowing field practitioners access to such an instrument could facilitate patients' monitoring of urinary sodium output, potentially improving patients care and overall population health.

To determine the validity and intra- and inter-instruments reliability of two portable, easy-to-use and inexpensive sodium analyzers.

Urine samples (N= 77) were collected from 31 men and compared against reference values of an ion chromatograph.

Both analyzers demonstrated excellent absolute (95% limits of agreement (LoA) of ± 3-4%) and relative intra-instrument reliability (intraclass correlation coefficients (ICC) of 1.00). Inter-instruments relative reliability was excellent (ICC: 0.99), whereas absolute reliability was good (95% LoA of ± 13%). Compared with results obtained by ion chromatography, relative validity was excellent for both analyzers. Absolute validity was good-to-moderate (95% LoAs ranging from ± 15% to ± 20%).

A low cost, portable analyzer can reliably be used by field practitioners to monitor changes in urinary sodium excretion across time and provide adequate guidance for individuals on sodium-restricted diets.