The diagnostic performance of human urinary dipsticks to estimate urine pH, specific gravity (SpG), and protein in horses: are they reliable?

Abstract

Background Urinalysis is a critical diagnostic test which is performed in routine veterinary medicine practice. In this diagnostic test, semiquantitative measurement of urine biochemical substances is carried out using urinary dipstick. In the current study, we evaluated the diagnostic performance of human urinary dipsticks to estimate pH, specific gravity (SpG), and protein in 80 urine specimens collected from horses. These parameters were measured using two commercial human dipsticks (KP and MN in abbreviation) and quantitative reference methods. The reference methods for pH, SpG, and protein were pH meter, handheld refractometer, and pyrogallol red method, respectively. The correlation between the semiquantitative dipstick analysis and quantitative reference methods was determined using Spearman’s rank correlation coefficient. Results In general, our results revealed that the both human urinary dipsticks are unreliable tests for urinary pH, SpG, and protein content in horses. The analysis indicated that there was a poor correlation between the urine dipsticks and reference method (KP: r S = 0.534 and MN: r s = 0.485, Ps < 0.001) for protein. Additionally, there was a weak correlation between the results of pH measured using the urine dipsticks and reference method (KP: r S = 0.445 and MN: r s = 0.370, Ps < 0.001). Similar findings were obtained for SpG (KP: r S = 0.285, MN: r s = 0.338, Ps < 0.001). The estimation of proteinuria using the human dipsticks in horses lacked specificity, as many false positive protein results were obtained. Conclusion We observed that the human commercial urinary dipsticks used in this study were not reliable to correctly estimate urine protein, SpG, and pH in horses.

Urinalysis in dog and cat: A review

“…The glomerulus is a kidney structure that functions as a filter that is freely permeable to water, solutes but retains cells and most macromolecules, such as albumin and globulin [37]. Total urine protein can be measured with urine dipstick, sulfosalicylic acid (SSA) (sulfosalicylic test), or urine protein creatinine (UPC) ratio [38]. Protein test strip primarily measures albumin and is more specific to it than globulin [39].…”

An updated review: Laboratory investigation of equine renal disease

“…Two types of reagent strip were recently demonstrated to be unreliable for the measurement of equine urinary pH (Hekmatynia et al . 2019).…”

“…Two types of reagent strip have demonstrated unreliability for the assessment of equine USG (Hekmatynia et al . 2019). Use of a refractometer is recommended instead.…”