The utility of combined urine dipstick analysis and specific gravity measurement to determine feline proteinuria

Abstract

Objectives To assess the utility of urine dipstick strips for detection of feline proteinuria when used in combination with urine‐specific gravity, compared with urine protein‐to‐creatinine ratio as the gold standard. Materials and Methods Retrospective analysis of clinical records of comprehensive urine examination obtained from cats presented to a referral hospital. Diagnostic agreement and test accuracy were calculated for the dipstick test alone and in combination with the urine‐specific gravity, using different cut‐off values for proteinuria. Receiver‐operating characteristic curves were also calculated. Results A total of 121 urine samples were included. The diagnostic agreement between dipstick and urine protein‐creatinine ratio was poor. A dipstick result of equal or greater than “Trace” (0.1–0.3 g/L) had a sensitivity of 81% and a specificity of 31% to detect proteinuria. Grouping the samples by urine‐specific gravity did not increase dipstick agreement with the urine protein‐creatinine ratio and only resulted in a slight improvement in the accuracy of detecting proteinuria. Clinical Significance The dipstick test was not accurate for detecting proteinuria when combined with urine‐specific gravity in cats. Clinicians should not rely on this test and, regardless of the urine concentration, other appropriate quantitative methods such as urine protein‐creatinine ratio should always be performed to detect proteinuria in cats.

Urinary Protein/Creatinine Ratio in Feline Medicine: Reasons to Perform It and Its Role in Clinical Practice—A Retrospective Study

“…In contrast to dogs, this study highlights that it is not possible to predict levels of feline proteinuria from the combination of dipstick tests and USG. This was also recently suggested by Pérez-Accino et al [ 21 ]. For the reasons stated above, we advise the systematic use of UPCR to diagnose proteinuria in cats, following the International Renal Interest Society recommendation [ 4 , 22 ].…”

“…Although the urine was yellow, the urinary pH was 8.5. Since alkaline urine may induce false-positive results on a dipstick proteinuria test, this was considered a false-positive [ 21 , 22 ]. In contrast to dogs, this study highlights that it is not possible to predict levels of feline proteinuria from the combination of dipstick tests and USG.…”

Evaluation of a urine dipstick protein to urine specific gravity ratio for the detection of proteinuria in dogs and cats

“…Although we did not find any difference in correlation between UPCR and DUR in cats, no cats had hyposthenuric samples and a difference in correlation might still exist when comparing very dilute with very concentrated samples. However, when evaluating the use of urine dipsticks for protein detection in cats, a previous study found that the grouping of urine samples based on USG did not improve the accuracy of the dipstick result to predict UPCR 20 . Another study in dogs evaluating the relationship between USG and UPCR reported that although mild to moderate negative correlations existed between these 2 variables, the use of a predictive equation could not reliably predict the UPCR based on dipstick protein results 7 .…”

“…7 Likewise, evaluating feline urine samples, another previous study reported that, for the detection of a UPCR >0.2, the application of a USG cutoff >1.035 moderately improved the accuracy of dipstick protein readings but did not improve agreement between dipstick and UPCR results. 20 T A B L E 5 Diagnostic accuracy of dipstick USG ratio (DUR) for the detection of proteinuria in cats. Abbreviations: AUC, area under the curve; CI, confidence interval; NPV, negative predictive value; PPV, positive predictive value; UPCR, urine protein creatinine ratio.…”

Die Urinuntersuchung bei Hund und Katze, Teil 1: Physikalische und chemische Urinuntersuchung

“…In 2 Studien lag die Sensitivität des Proteintestfeldes für Katzenurin (Cut-off 30 mg/dl) zwischen 64 % und 100 % und die Spezifität zwischen 41 % und 70 % [52,84]. Auch in Kombination mit dem USG kann bei Katzen der Grad der Proteinurie durch den Teststreifen nicht vorhergesagt werden [84,90]. Sowohl positive als auch negative Reaktionen des Proteintestfeldes sind bei Katzen höchst unzuverlässig [52,84,90].…”