Proteinuria is presence of significant protein in the urine and is an indication of kidney disease.

• Small increases in degree of proteinuria or albuminuria indicate kidney disease
• Persistent proteinuria is highly associated with loss of renal function over time
• The degree of proteinuria correlates well with the rate of loss of renal function
• Proteinuria is an independent predictor of increased risk of cardiovascular death

Several authors have published articles on use of single urine samples to quantify proteinuria by use of urine protein to urine creatinine ratio.

Correlation of single urine sample calculations correlate well with formal 24 hour urinary protein in patients with a broad spectrum of renal diseases, varying degrees of proteinuria, pregnancy, and a wide range of glomerular filtration rates.

Using this technique (instead of 24 hour collection), the urine is preferred to be a First Morning Specimen; however random specimens are acceptable if first morning specimen is not available.

The formula used is:

Protein Excreted = UrineProtein/UrineCreatinine

As this computation is a ratio, the units for both values should be identical, whether they be mmol/L, mg/dL, g/L or other units.

Interpretation:

• Protein/Creatinine ratio of <0.2 is normal
• Protein/Creatinine ratio of >=0.3 highly correlates with 24 hour protein excretion of >=300 mg/24 hrs
• Protein/Creatinine ratio of >3.5 is nephrotic range proteinuria

References

Agarwal I, et al. Quantitation of Proteinuria By Spot Urine Sampling. Indian J Clin Biochem. 2004;19(2):45-7.

Eknoyan G. On testing for proteinuria: Time for a methodical approach. Cleveland Clinic Journal of Medicine. 2003 Jun;70(6):493-501.

Ginsberg JM, et al. Use of single voided urine samples to estimate quantitative proteinuria. N Engl J Med. 1983 Dec 22;309(25):1543-6.

Houser M. Assessment of proteinuria using random urine samples. J Pediatr. 1984 Jun;104(6):845-8.

Leaños-Miranda A, et al. Protein:creatinine ratio in random urine samples is a reliable marker of increased 24-hour protein excretion in hospitalized women with hypertensive disorders of pregnancy. Clin Chem. 2007 Sep;53(9):1623-8.

Leaños-Miranda A. Random urine protein:creatinine ratio was an accurate method for diagnosing proteinuria in pregnant women with hypertension. Evid Based Med. 2008 Jun;13(3):84.

Schwab SJ, et al. Quantitation of proteinuria by the use of protein-to-creatinine ratios in single urine samples. Arch Intern Med. 1987 May;147(5):943-4.