Creatinine is a by-product of muscle metabolism. Creatinine is excreted in urine at an approximately constant rate, which means it can be used as a standard for comparison for other substances that are also excreted in the urine. For this test, urine creatinine levels are used to standardize urine protein levels for fluctuations in urine concentration driven by the patient’s level of hydration.
UPC - Domande frequenti
No. The UPC ratio should be performed only on urine that is free of blood and inflammatory cells. A complete urinalysis and sediment evaluation should be completed to determine if the sample is suitable for the UPC Ratio test. The presence of blood and inflammation in urine may give a falsely high result for the UPC Ratio, suggesting there is kidney disease when none is actually present.
Quali sono gli intervalli di riferimento per i singoli parametri, proteine urinarie (UPRO) e creatinina urinaria (UCRE)?
We don’t have reference ranges for urine protein and urine creatinine. The individual urine protein and urine creatinine results should not be evaluated on their own since the individual measurements (UPRO and UCRE) can change significantly within a short time frame, and are sensitive to urine volume and concentration. The benefit of the UPC ratio is that it automatically corrects for variations in urine volume and concentration.
Proteinuria can be transient and not associated with renal disease. Therefore, it must be determined to be persistent. Persistent renal proteinuria in nonazotemic animals is a sign of early renal disease. After the urine protein is localized to the kidney and evidence of lower urinary tract disease is not identified, it must be determined to be persistent. Persistence in nonazotemic animals is determined by identifying proteinuria on three or more occasions at least two weeks apart. By detecting the damage to the kidneys before azotemia is present and the patient’s urine concentration ability is impaired, the veterinarian can minimize disease progression and improve the patient’s prognosis. If the animal is azotemic and proteinuric, and lower urinary tract disease is excluded, the proteinuria can be attributed to renal disease.
I medici veterinari hanno rilevato per anni la proteinuria mediante dipstick. Questa valutazione non è quindi sufficientemente accurata?
Unfortunately, many veterinarians today are depending on the urine protein dipstick dye test to determine proteinuria. But this test is neither sensitive nor specific, and can often yield erroneous results. “If you’re interested in detecting a low level of protein in the urine, the dipstick is not sensitive enough. We’re going to get a lot of false-positives, but we may also see some false-negatives with a low proteinuria level. The sulfosalicylic acid, urine microalbumin, and urine protein:creatinine ratio tests are much more sensitive than the dipstick at detecting these lower concentrations of protein in the urine." Dr. Gregory F. Grauer1 Because of poor specificity of the dipstick as a screening tool, IDEXX Reference Laboratories routinely performs a confirmatory SSA with any urinalysis when a dipstick assay is positive for protein. The SSA test result is included in the urinalysis report. “The standard dipstick tests for protein are of little help when screening cat urine because there are so many false-positives. There are two possible approaches: 1) run a urine protein:creatinine ratio initially and forget the screening test, or 2) screen with the microalbuminuria test." Dr. Jonathon Elliott1 Regardless of the screening test used, initial discovery of proteinuria requires localization, proof of persistence and tracking of trends via the UPC ratio. “We mainly use serial urine protein:creatinine ratios to evaluate proteinuria magnitude because they are useful for measuring any level of proteinuria." Dr. George E. Lees1 1 Advanstar Communications. Proteinuria and Renal Disease: A Round-Table Discussion. Lenexa, Ka: Advanstar Healthcare Veterinary Communications. 2005.
No. Protein can be present in urine if there is inflammation or bleeding anywhere in the urinary system. Protein that comes from inflammation or bleeding is not as worrisome, because the urinary protein loss will stop once the underlying problem is treated or corrected. This is why a urine sediment exam is necessary in conjunction with a UPC Ratio; clean urine sediment is needed to ensure that any subsequent protein detected is of kidney origin.
The UPC Ratio must be interpreted in the context of the other kidney function tests like UREA, CREA and SDMA. We recommend using IRIS guidelines for interpreting UPC Ratio results.
Several studies indicate a strong correlation between the UPC result and patient prognosis. The higher the UPC Ratio, the worse the prognosis. Since the IDEXX UPC Ratio is fully quantitative, the veterinarian can use this test not only to diagnose renal disease, but also as a prognostic indicator. Sequential UPC Ratios can be used to monitor patient response to treatment and disease progression.
Proteinuria refers to an excessive amount of protein detected in the urine. Urine protein can be a complex combination of components that may include albumin, globulins, immunoglobulin light chains and low molecular-weight proteins. Microalbuminuria refers to the measurement of small quantities of albumin in the urine. In other words, microalbuminuria alludes to a small urine albumin concentration, typically <30 mg/dL, which is undetectable by semi-quantitative dipstick tests. The IDEXX UPC Ratio measures all fractions of urine protein, including albumin. Different methodologies used for the urine protein measurement will have variable sensitivities to different protein fractions, especially the globulin fractions. However, almost all methodologies will detect the albumin fraction.
Yes, it is important to detect the other proteins in addition to the albumin. In renal diseases, albumin can be the predominant protein; however, other urine protein fractions may also be present, and these concentrations can vary, depending on the underlying condition. Immunoglobulins and other proteins can have an impact on the urine protein results, depending on the nature of the underlying disease.
Transient loss of a small amount of protein through the kidneys may not be critical if the kidneys are otherwise working well and producing concentrated urine. However, if kidney function is compromised and the kidneys are producing dilute urine, then even small amounts of urinary protein loss may be abnormal and should be investigated. Substantial and/or persistent protein loss through the kidneys is a concern because it means the kidneys are not working properly. It is also worrisome because the body is losing protein, which is a precious substance needed for long-term health and well-being.
An elevated IDEXX UPC Ratio indicates that there is a clinically significant amount of protein in the urine. To determine if renal disease is responsible for this urinary protein loss, you must first localize the protein loss to the kidneys by ruling out prerenal and postrenal causes (via a history, PE, CBC, biochemical profile and a complete urinalysis). And because the test is so sensitive, you must rule out transient proteinuria (which can be caused by fever, exercise and changes in temperature) to determine that the proteinuria is persistent.
Because the UPC ratio is so sensitive, it can detect very small amounts of protein in the urine that are of a transient nature. You have to rule out this transient, or functional proteinuria, which can be associated with increases in blood pressure as well as stress, exercise and fever, in order to determine that the protein is significant.
Il risultato del rapporto urinario proteine/creatinina può essere usato per monitorare la CKD nel cane e nel gatto?
Yes, when combined with tests such as SDMA, CREA, UREA and USG, the UPC Ratio is helpful in assessing the response to therapy and disease progression or regression in a given patient.
At this time, it has not been proven that medical intervention can physiologically reverse nephron damage. However, by catching the disease in an early stage, the veterinarian has the ability to prevent further damage and arrest disease progression.
Urine protein dipsticks are semi-quantitative and are influenced by urine pH, volume, concentration and color. While it is very easy to perform, the urine dipstick is neither a sensitive nor specific indicator of urinary protein loss. The lower limit of detection for urine protein on a dipstick is 30 mg/dL. The IDEXX UPC Ratio has a lower limit for urine protein of 5 mg/dL, and is highly specific for dog and cat proteinuria. Furthermore, the IDEXX Urine P:C Ratio corrects for variations in urine concentration and volume. You should perform a Urine P:C Ratio on all suspect renal disease patients regardless of a negative urine protein dipstick result.