Urine pH is frequently monitored in dogs with urolithiasis, urinary tract infections, and other diseases. Because of costs and convenience, commercially available urine reagent test strips are used to determine urine pH, but they may not be sufficiently accurate for evaluation of some diseases. This study evaluated a laboratory benchtop pH meter, 4 portable pH meters, a commercial urine reagent strip, and pH paper. Reproducibility and accuracy were measured in pooled urine samples. Dog and cat urine is produced at a pH of 5 to 8. During the reproducibility study, pooled samples from 15 dogs had a pH of 6.11 or 6.60.  Hydrochloric acid or sodium hydroxide was added to samples to achieve the pH of 5.50 and 7.60. For the accuracy study, 201 voided urine samples from hospitalized dogs were used. Reagent strips and pH paper tended to overestimate the pH values obtained from the benchtop meter: the reagent strip had the largest variability at pH values of 6 to 7.5, and the pH paper had the largest ranges at pHs of 6 to 8.

COMMENTARY: Portable pH meters should be used instead of reagent test strips when making therapeutic decisions based on urine pH. Values obtained from reagent test strips should be considered estimates only.

Evaluation of the reproducibility and accuracy of pH-determining devices used to measure urine pH in dogs. Johnson KY, Lulich JP, Osborne CA. JAVMA 230:364-369, 2007.