Proteinuria Calculator

Variables and formula

In order to estimate the rate of urinary protein excretion, the proteinuria calculator uses the results from a urinary probe (based on 24-hour collection):

■ Urine protein in mg/dL;

■ Urine creatinine, measured in mg/dL.

The formula that contributes to the screening of patients at risk of kidney disease is:

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

Protein/creatinine ratios of 0.2 are considered within normal limit whilst ratios greater than 3.5 indicate "nephrotic-range" proteinuria in the presence of stable renal function.

The usage of proteinuria (through the Up/Ucr has established through random urine sample analysis) on a test population found that the ratio can replace collection of timed urine samples.

However, an indication remains in regard to the urine sample with best correlation which is the first voided morning specimen.

About proteinuria

The kidneys filter proteins which are to remain in the blood. When kidney function is altered, because of one reason or another, nephrotic syndrome occurs and proteins pass in the urine.

This may cause water retention in the areas of ankles, hands and around the eyes.

Persistence of proteinuria is a sign of an increase in glomerular permeability (which allows the filtration of normally non-filtered macromolecules).

These are some of the conditions associated with this phenomenon:

■ Kidney damage;

■ Diabetic kidney disease or cysts;

■ Urinary tract infection;

■ Heart failure;

■ Bladder tumor;

■ Dehydration.

The main complication of long term, untreated proteinuria, is kidney failure. Because there are no specific symptoms, the only way to diagnose proteinuria is through laboratory tests.

The commonly used method, the dipstick test, measures urinary proteins (such as albumin) in the sample with a color sensitive pad. The test will be positive where kidney disease is present, even if the protein levels are not increased.

Normal protein values in a random urine sample are between 0 and 20 mg/dL, depending on laboratory.

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

There are several conditions that may affect the result of the test, such as urinary tract infections, dehydration, some medications or vaginal secretions.

References

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

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

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

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