A saliva urea test strip for use in feline and canine patients: a pilot study

We evaluated a saliva urea test strip (Kidney-Chek; SN Biomedical), as a rapid, noninvasive method to screen for azotemia. The test is a semiquantitative method that assesses 7 levels of saliva urea concentration, and indirectly serum urea, from <3 to >17 mmol/L. Ninety-two dogs (14 azotemic) with serum urea of 1.3-37 mmol/L and 56 cats (16 azotemic) with serum urea of 4.1-89.3 mmol/L were enrolled. A positive correlation was found for saliva urea against serum urea in each species (dogs: r_s = 0.30, p < 0.005; cats: r_s = 0.50, p < 0.001). After turning the semiquantitative data into continuous data by attributing to each level the midpoint of the described range, a receiver operating characteristic curve analysis showed good performance for detecting serum urea above the upper limit of the laboratory RI (dogs: 2.1-11.1 mmol/L; cats: 5-12.9 mmol/L), with an area under the curve of 0.81 in dogs and 0.83 in cats. We recommend that the test be used as an exclusion test, given that it cannot confidently confirm azotemia with higher test results. Additional investigations are recommended for dogs with a test strip reading of ≥9-11 mmol/L and for cats with a test strip reading of ≥12-14 mmol/L.