Abstract: Background: The urine protein:creatinine ratio (UPC) is the gold standard for quantifying proteinuria. This this is not always performed, limiting retrospective analysis of proteinuria. The urine dipstick protein:urine specific gravity (DP:USG) ratio has recently been used as marker for proteinuria, although this test has not been validated against UPC.
Objective: To investigate the correlation between DP:USG and UPC in dogs.
Animals: Dogs who had urinalysis and UPC performed for any reason.
Methods: Retrospective case study. The DP:USG was calculated and compared to UPC as continuous and categorical variables using a cutoff >1.5 as abnormal.
Results: 377 dogs were identified through retrospective medical record search. 216 dogs (58.7%) were excluded because the DP:USG could not be determined due to negative (n=168, 43.1%) or trace (n=61, 15.6%) dipstick urine protein results. 33 (15.3%) of the dogs with negative or trace dipstick proteinura that could not undergo DP:USG evaluation had UPC >0.5. DP:USG was significantly associated with UPC (p< 0.0001, r=.725). The DP:USG cutoff of >1.5 was 93.6% sensitive, 68.6% specific, and had 88% accuracy at identifying dogs with a UPC >0.5.
Conclusions and Clinical Importance: DP:USG is fairly reliable to predict UPC >0.5 only when 1+ protein is detectable via dipstick. DP:USG is not an appropriate substitute for UPC when quantifying the degree of proteinuria, nor should it be used to reliably quantify the magnitude of proteinuria. Absent and trace dipstick proteinuria precludes DP:USG measurement and fails to identify some proteinuric dogs.
