From the Guidelines
The main difference between urine protein-to-creatinine ratio (UPCR) and urine protein-creatinine index (UPCI) lies in their calculation and units, with UPCR providing a dimensionless ratio and UPCI resulting in a value with units. The UPCR is calculated by dividing the urine protein concentration by the urine creatinine concentration, typically expressed as mg/mg or g/g, whereas UPCI is calculated using different units for protein and creatinine, often mg/mmol. Both measurements serve similar clinical purposes, helping to assess proteinuria without the need for a 24-hour urine collection, which is more convenient for patients and correlates well with 24-hour protein excretion 1. They are useful for monitoring kidney disease, preeclampsia, and other conditions where protein leakage is significant, with the choice between UPCR and UPCI often depending on regional laboratory preferences and reporting conventions. However, it's worth noting that the measurement of urinary albumin-to-creatinine ratio (ACR) is recommended for the evaluation of proteinuria in preference to urinary total protein, as albumin is the most important protein lost in the urine in most cases of chronic kidney disease (CKD) 1. Key points to consider include:
- UPCR and UPCI provide similar information about kidney function and protein excretion
- The choice between them often depends on laboratory preferences
- Urinary ACR is preferred for evaluating proteinuria in CKD due to its greater sensitivity for detecting low-grade but clinically important albuminuria 1. In clinical practice, the distinction between UPCR and UPCI may not significantly impact patient management, as both are used to assess proteinuria and monitor kidney disease progression, but using the most appropriate and consistent measurement is crucial for accurate monitoring and decision-making.
From the Research
Difference between UPCr (ratio) and UPCI (index)
- UPCr (urine protein-to-creatinine ratio) is a measure of the amount of protein in the urine compared to the amount of creatinine, which is a waste product found in urine 2, 3, 4.
- UPCI (urine protein-to-creatinine index) is not explicitly defined in the provided studies, but it can be inferred that it might be related to the urine protein-to-creatinine ratio.
- The main difference between UPCr and UPCI is that UPCr is a ratio, while UPCI is an index, which might imply a different method of calculation or interpretation.
- Studies have shown that UPCr is a reliable and simple test for monitoring proteinuria, with a strong correlation to 24-hour urine protein estimation 2, 4.
- The use of UPCr has been advocated for in daily practice to derive the urinary albumin-to-protein ratio (uAPR) and urinary non-albumin protein (uNAP), which can provide a better mortality prognostic assessment 3.
Key Findings
- A study found that a UPCr of 0.1171 reliably predicted 24-hour urine total protein equivalent of > 150 mg/24 hrs with sensitivity 100% and specificity 98.1% 2.
- Another study found that a UPCr cut-off value of 2.4 had 96.9% sensitivity and 82.5% specificity for delineating between grade 2 and 3 proteinuria 4.
- The use of UPCr and uACR (urine albumin-to-creatinine ratio) can provide a better understanding of proteinuria and mortality risk 3.
Clinical Applications
- UPCr can be used to monitor proteinuria in patients with chronic kidney disease, and its use has been recommended as a first-line agent in diabetic renal disease and non-diabetic renal disease with albuminuria 5.
- The measurement of UPCr can help identify patients at risk of progression of renal disease and enable timely intervention 6, 5.