From the Guidelines
A Urine Protein to Creatinine (UPC) ratio test should be ordered when screening for or monitoring proteinuria in patients with suspected or confirmed kidney disease, particularly those with diabetes, as recommended by the national kidney foundation practice guidelines for chronic kidney disease 1. When to order a UPC test is largely dependent on the clinical context, including the presence of conditions that increase the risk of kidney damage.
- The test is indicated for patients with diabetes, hypertension, or other conditions that increase the risk of kidney disease.
- It is also useful when dipstick urinalysis shows protein, when evaluating patients with chronic kidney disease, during pregnancy to assess for preeclampsia, or when monitoring patients on nephrotoxic medications.
- The UPC ratio is preferred over a 24-hour urine collection because it's more convenient and provides comparable diagnostic information from a single spot urine sample, as noted in the guidelines for chronic kidney disease evaluation and management 1. The UPC ratio works by comparing protein concentration to creatinine concentration, which controls for urine concentration variability.
- A ratio greater than 0.2 in adults is considered abnormal, with values above 3.0 suggesting significant proteinuria often seen in nephrotic syndrome.
- Regular monitoring with UPC ratio tests allows for timely intervention and treatment adjustments in kidney disease management, aligning with the recommendation for quantitative assessment of proteinuria for detection, differential diagnosis, prognosis, and treatment of chronic kidney disease 1.
From the Research
When to Order a Urine Protein to Creatinine Ratio (UPC) Test
The Urine Protein to Creatinine Ratio (UPC) test is a useful diagnostic tool for detecting and estimating proteinuria, which is the presence of excess proteins in the urine. This test can be used in various clinical settings, including:
- Diagnosis of kidney disease, hypertension, gestational hypertension, preeclampsia, immunological diseases, diabetes mellitus, and multiple myeloma 2
- Monitoring of proteinuria in patients with existing kidney disease or other conditions that affect the kidneys 3
- Assessment of kidney function in healthy individuals and patients with kidney disease 4
Indications for Ordering a UPC Test
A UPC test may be ordered in the following situations:
- When a patient presents with symptoms such as hematuria, edema, or hypertension, which may indicate kidney disease 2
- As part of a routine urinalysis to screen for proteinuria in patients with risk factors for kidney disease, such as diabetes or hypertension 4
- To monitor the effectiveness of treatment in patients with existing kidney disease or proteinuria 3
- In pregnant women at risk of preeclampsia, as recommended by the International Society for the Study of Hypertension in Pregnancy 2
Interpretation of UPC Test Results
The results of a UPC test are interpreted based on the ratio of protein to creatinine in the urine. A ratio of:
- < 100 mg/g is considered normal 4
20 mg/mmol (0.2 mg/mg) is indicative of proteinuria 2
350 mg/mmol (3.5 mg/mg) is indicative of nephrotic proteinuria 2
30 mg/mmol (0.3 mg/mg) is used to classify proteinuria in pregnant women at risk of preeclampsia 2
Limitations of the UPC Test
The UPC test has some limitations, including:
- The test may not be accurate in patients with very high or very low levels of proteinuria 5, 6
- The test may be influenced by urine concentration, with dilute urine samples potentially leading to overestimation of proteinuria and concentrated urine samples potentially leading to underestimation 5
- The test may not be suitable for all patient populations, such as those with nephrotic-range proteinuria 6