Proteinuria Calculator

How does this proteinuria calculator work?

This health tool estimates the quantity of excreted proteins based on the protein/creatinine quantities in urine.

Proteins excreted in urine offer information of kidney function and allow the screening of patients at risk of kidney disease.

The two fields to be completed in the proteinuria calculator are:

■ Urine protein (Up) in probe measured in mg/dL.

■ Urine creatinine (Uc) in probe measured in mg/dL.

The formula used is the following:

Urinary proteins excreted (g/day) = Urine protein / Urine creatinine

One of the studies cited, refers to protein/creatinine ratios of more than 3.5 as representing "nephrotic-range" proteinuria in the presence of stable renal function. Same concludes that a ratio of 0.2 is within normal limits.

One of the studies on the feasibility of assessing proteinuria through the Up/Ucr has established through random urine sample analysis on the test population that the ratio can replace collection of timed urine samples in most cases.

This is because the protein/creatinine ratio in a single urine sample can correlate with protein excretion that is classically measured in the 24-hour urine collections.

Some indication in regard to the timing of the urine sample with best correlation has been made and the result refers to the first voided morning specimen.

Proteinuria guidelines

Normally, proteins are not filtered by the kidneys and remain in the blood. When kidneys are damaged due to different conditions, nephrotic syndrome occurs and proteins will pass.

Proteinuria itself doesn’t have any specific symptoms and can only be detected through testing.

The dipstick test with a color sensitive pad measures urinary proteins in the sample, like albumin. In some cases, the 24h urine collection may be required. More sensible tests, such as the urine micro albumin test detect smaller amounts of albumin. In cases where kidney disease is diagnosed, usually the dipstick test will be positive, even regardless of blood protein levels.

Dehydration, any urinary tract infections, vaginal secretions, strenuous exercise or medication can influence test results, therefore should be disclosed beforehand.

Normal values for random urine samples vary between 0 to 20 mg/dL, also depending on laboratory.

Nephrotic syndrome creates water retention in the areas of ankles, hands and around the eyes.

Laboratory results of urine samples come as “protein-creatinine ratio” (PCR) or by “albumin-creatinine ratio” (ACR).

High urinary proteins that persist are connected to an increase in glomerular permeability (which allows the filtration of normally non-filtered macromolecules) may indicate:

■ Kidney damage;

■ Diabetic kidney disease or cysts;

■ Heart failure;

■ Urinary tract infection or bladder tumor;

■ Dehydration.

When high abnormal results are found the patient is referred for blood tests, full history and ultrasound exams. After this, in some cases, kidney biopsy might be necessary.

The main complication of long term, untreated proteinuria, is kidney failure. Treatment is customized based on patient data and cause. In most cases, a reduction in salt and water intake is recommended.

References

1) Schwab SJ, Christensen RL, Dougherty K, Klahr S. (1987) Quantitation of proteinuria by the use of protein-to-creatinine ratios in single urine samples. Arch Intern Med; 147(5):943-4.

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

3) Ginsberg JM, Chang BS, Matarese RA, Garella S. (1983) Use of single voided urine samples to estimate quantitative proteinuria. N Engl J Med; 309(25):1543-6.

4) Smith ER, Cai MM, McMahon LP, Wright DA, Holt SG. (2012) The value of simultaneous measurements of urinary albumin and total protein in proteinuric patients. Nephrol Dial Transplant; 27(4):1534-41.

5) Martin H. (2011) Laboratory Measurement of Urine Albumin and Urine Total Protein in Screening for Proteinuria in Chronic Kidney Disease. Clin Biochem Rev; 32(2): 97–102.