Potentiometric method vs reagent strip: A comparison of pH in urine samples

Abstract

Introduction: Urine has multiple chemical compounds and salts that are often related to the patient's symptoms. These compounds have various functional groups that determine the urinary pH accompanied by the electrolyte balance. Objective: The present study aimed to compare the pH parameter obtained by two brands of test strips with the potentiometric method, also associating it with urinary osmolarity. Materials and methods: 80 urine samples from apparently healthy patients were studied, in which no exclusion criteria were considered. To measure pH, two commercial brands coded as TR1 and TR2 and a Thermo Scientific Orion Lab Star PH111 peachimeter were used. Results: neither of the two brands coincided with the pH value obtained by the peachimeter, and there was also variability between both for the same sample. No correlation was observed between the pH measured by the test strips and urinary osmolarity. The TR2 brand showed pH values in 16 of the 80 samples, obtaining pH values between 7.7 and 8.1 in these same samples with the peachimeter. In 9 of these 16 samples mentioned the pH values were below 6.5 with the TR1 brand. Conclusions: It is evident that there is a lot of discrepancy when establishing the urinary pH by reagent strips when it is close to 7, for this reason it is advisable to establish a criterion to report only this parameter as layered or alkaline if it is not measured by peachimeters.