Urinary Protein Excretion Estimation
Quantifies 24-hour proteinuria with protein/creatinine ratio from a single urine sample.
Avoid using overnight or first morning void as urine sample.
When to Use
- Patients in whom renal disease is suspected (to rule out).
- Patients with known renal disease (to assess progression).
- Patients with low-grade proteinuria and otherwise intact renal function (to monitor).
- The Urinary Protein Excretion Estimation (sometimes referred to as “spot urine protein/creatinine ratio” or “protein/creatinine ratio”) calculates the protein/creatinine ratio from a random urine sample to estimate 24-hour protein excretion.
- Based on the physiologic principle that urinary creatinine excretion is constant if glomerular filtration rate (GFR) is constant and therefore protein/creatinine ratio from a single urine sample should reflect protein excretion, cancelling out the time factor.
- Confirmed for correlation with 24-hour protein excretion in multiple studies (see Evidence Appraisal/EBM).
- Correlation is lowest for urine samples voided overnight and upon arising.
- Can be used only in presence of stable renal function (GFR).
- If albumin is the predominant component, persistent proteinuria suggests renal disease, even in the absence of decreased glomerular filtration rate, hypertension, or other abnormal findings on urinalysis.
- 24-hour urine collection is time consuming, inconvenient for patients, and subject to collection error. The Urinary Protein Excretion Estimation avoids these problems without sacrificing accuracy, by using a single urine sample.
- Proteinuria is an independent risk factor for cardiovascular and renal disease, and predicts end organ damage. Detecting an increase in protein excretion has both diagnostic and prognostic value in initial detection and confirmation of renal disease.
- Quantifying proteinuria can also help assess effectiveness of therapy and progression of disease.