Evaluation of various rapid chloride tests for assessing urinary NaCl excretion.

Background/aims: The evidence linking NaCl intake to high blood pressure and probably to other diseases has become stronger. Therefore, a population-wide reduction of NaCl intake is generally recommended. Measuring NaCl excretion in urine is the preferred method for estimating dietary NaCl intake. Rapid tests measuring urinary NaCl excretion might be useful for self-monitoring the individual NaCl consumption.

Methods: The accuracy of four rapid tests measuring chloride content in urine was assessed. Three tests were originally not designed for urine analysis, but for water and food analysis. Totally 204 urine samples were analysed both with the 4 different rapid tests and with quantitative routine laboratory procedures for chloride and sodium.

Results: Chloride and sodium were highly correlated (r = 0.96), indicating chloride determination as a reasonable method to assess sodium and NaCl contents in urine. Accuracy of the rapid tests was acceptable in three cases. The drawback of two tests was their narrow calibration range, so that most urine samples had to be diluted. Use of one test showed problems in interpreting its results because the decolouration of the test pads was difficult to recognize.

Conclusion: It is concluded that rapid chloride tests designed for water analysis might be suitable to determine NaCl in urine samples.