Objectives:
Measurement of mean population sodium and potassium intake typically
using laboratory -based assays which can add significant logistical burden and costs. A valid field-based measurement method would be a significant advance. In this study, we used 166 24 -hour urine collection samples to compare estimates of sodium, potassium content and sodium/potassium ratio based upon assays done using the field-
based Horiba twin meter versus a laboratory-based method.

Design:
Aliquots of urine were assayed for sodium and potassium using the ion-selective electrode method with the field-based Horiba twin meter and the laboratory-based method. The performance of the Horiba twin meter was determined by comparing field-based estimates of mean
sodium and potassium against those obtained using the laboratory-
based methods.
Setting:
24-hour urine samples were collected as part of an ongoing study being done in rural China.

Subjects:
There were 166 subjects complete 24-hour urine samples available for estimating 24-hour urinary sodium and potassium excretion.

Results:
Mean sodium and potassium excretion were estimated as 170.4 mol/day and 37.4 mmol/day using the meter-based assays and 193.4 mmol/day and 43.8 mmol/day using the laboratory-based assays. There was excellent relative reliability for both sodium (ICC=0.986) and potassium (ICC=0.986). Bland-Altman plots showed moderate-to-good
agreement between two methods.

Conclusions:
Sodium and potassium intake estimation was moderately under-
estimated using assays based upon the Horiba twin meter. Compared to standard lab-based methods, the portable device was more practical and convenient.