Protein Creatinine Ratio Calculator

Created by Joanna Michałowska, PhD candidate
Reviewed by Dominik Czernia, PhD candidate and Jack Bowater
Last updated: Feb 15, 2022

The protein creatinine ratio calculator determines proteinuria based on a spot urine sample. Urine protein creatinine ratio (UPCR) helps to identify patients with nephrotic range proteinuria and contributes to the screening of patients at risk of kidney disease. In the article below, you will find out more about proteinuria and learn how to calculate the protein creatinine ratio.

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Urine protein creatinine ratio (UPCR)

Proteinuria is recognized as an independent risk factor for cardiovascular and renal disease, and as a predictor of organ damage, however, the reference test, a 24-hr urine protein estimation, is known to be unreliable. As the excretion of creatinine and protein is rather constant throughout the day (provided that the glomerular filtration rate is stable), some researchers have proposed the use of a protein creatinine ratio measurement in urine samples collected over a short period of time, or even random (spot) urine samples.

How to calculate protein creatinine ratio

There are only two variables needed to estimate the rate of urinary protein excretion. You don't need to know the urine volume or output for the calculation of UPCR, just the

  • Urine protein (expressed in mg/dL); and
  • Urine creatinine ( expressed in mg/dL).

The following formula the protein creatinine ratio calculation:

Urinary protein excretion (g/day) = Urine protein / Urine creatinine

The normal range for urine protein should not exceed 15 mg/dL, while the reference range for spot urine creatinine is not established yet. Its value depends on many factors, such us diet, body weight, lean body mass, exercise, etc.

Protein creatinine ratio - interpretation

According to the research of Ginsberg et al. the following interpretation of the protein creatinine ratio should be implemented:

Protein creatinine ratio
Interpretation
less than 0.2
Normal range
0.2-3.5
Requires further investigation
more than 3.5
Nephrotic range

According to The Kidney Disease: Improving Global Outcomes (KDIGO) guideline, there are three categories of proteinuria, based on the protein creatinine ratio:

Protein creatinine ratio
Category
less than 1.5 g/day
Normal to mildly increased (A1)
1.5-5 g/day
Moderately increased (A2)
more than 5 g/day
Severely increased (A3)

Nephrotic range proteinuria

Kidneys filter proteins should remain in the blood, not urine. Proteinuria is the presence of excess proteins in the urine. An increase in protein excretion is widely used in the early detection of various conditions, e.g.:

  • preeclampsia;
  • diabetic nephropathy; and
  • nephrotoxicity attributable to drugs.

Severe proteinuria is associated with a nephrotic syndrome, which is characterized by a range of symptoms due to kidney damage. They include:

  • protein in the urine;
  • low blood albumin levels;
  • high blood lipids; and
  • significant swelling.

Nephrotic syndrome may be associated with many complications, e.g., blood clots, infections, protein malnutrition, and high blood pressure. The treatment of this disorder depends on the underlying cause.

Protein creatinine ratio calculator - a practical example

Let's calculate an exemplary urine protein creatinine ratio for a person with the following results:

  • urine protein - 2 mg/dl
  • urine creatinine - 120 mg/dl.
  1. We will be using the following equation to calculate protein creatinine ratio:

    Urinary protein excretion (g/day) = Urine protein / Urine creatinine

  2. After substituting the variables with the results, the formula looks as this:

    Urinary protein excretion (g/day) = 2 / 120

  3. Once this easy equation is solved, we can obtain the result:

    Urinary protein excretion (g/day) = 0.0167

  4. This protein creatinine ratio is within the normal range and does not indicate nephrotic range proteinuria.

References

  • Ginsberg et al. 1987; Use of Single Voided Urine Samples to Estimate Quantitative Proteinuria

  • Price et al. 2005; Use of Protein: Creatinine Ratio Measurements on Random Urine Samples for Prediction of Significant Proteinuria: A Systematic Review

  • The Kidney Disease: Improving Global Outcomes (KDIGO) 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (CKD)

Joanna Michałowska, PhD candidate
Urine protein
mg/dL
Urine creatinine
mg/dL
Protein creatinine ratio
g/day
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