Assessment of the effect of blood contamination on the urinary protein to creatinine ratio in the dog : a dissertation presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies in Veterinary Pathology at Massey University, College of Science, Turitea, Palmerston North, New Zealand
The urine protein to creatinine ratio (UPCR) is a reliable method to assess the total urinary protein loss in the dog from a single urine sample. Interpretation of the urine protein to creatinine ratio has been difficult in the presence of haematuria in the sample and previously the presence of blood in the urine has negated the use or interpretation of the UPCR. In 2 previous studies blood has been added to the urine sample of a single dog to aid interpretation of the UPCR in the presence of blood contamination. In this study blood contamination of urine samples in 21 dogs was assessed to develop guidelines for interpretation of the UPCR in the face of haemorrhage. Blood was added to the urine from the same dog to make samples with blood contamination levels ranging from 0 to 5%. Urine dipstick analysis, microscopic examination and a UPCR was performed on all samples. The current recommended cut off level for UPCR for normal dogs is <0.5. Results greater than 1.0 are considered abnormal, results greater than 2.0 suggests glomerular disease, and UPCR results between 0.5 and 1.0 are questionable. The results of the present study suggest that when urine is visibly red, haemorrhage may be considered as a differential for a UPCR up to 2.0. The practice of attributing proteinuria in non discoloured (yellow) urine samples with microscopic haemorrhage to the blood present should be discontinued, as microscopic haemorrhage that does not result in a visible change in colour of the urine sample from yellow will not substantially increase the UPCR. As such, the UPCR level in yellow urine even in the presence of microscopic haematuria can be considered valid.