What test should be used to measure total urinary protein rather than just albumin?

Measuring Total Urine Protein

Use the spot urine protein-to-creatinine ratio (PCR) to measure total urinary protein rather than albumin alone. 1, 2

Preferred Testing Method

• The spot urine PCR is the recommended test for quantifying total protein excretion and should be performed on a first morning void midstream sample whenever possible. 1, 2

• Express results as milligrams of protein per gram of creatinine (mg/g), with normal values <200 mg/g. 1

• The PCR performs equally well as 24-hour urine collections for predicting clinical outcomes (mortality, renal replacement therapy, and doubling of serum creatinine) while being far more convenient. 3

When to Measure Total Protein vs. Albumin

• Measure total protein (PCR) rather than albumin (ACR) in the following situations: 1

  • Children and adolescents, to detect both albuminuria and low-molecular-weight proteinuria 1
  • Very high levels of proteinuria (spot urine PCR 500-1,000 mg/g or higher) 1
  • Suspected tubular disease or paraproteinemia (e.g., multiple myeloma) 2
  • Kidney donor evaluation 2

• For adults with diabetes, albumin measurement (ACR) is preferred for initial screening, but total protein becomes acceptable at nephrotic-range levels. 1

Testing Algorithm

1. Initial screening: Use reagent strip urinalysis for total protein with automated reading (preferred) or manual reading. 1

2. Quantitative confirmation: If dipstick is positive (≥1+, 30 mg/dL), obtain a spot urine PCR within 3 months. 2

3. Confirm persistence: Obtain 2 of 3 positive quantitative tests over a 3-month period before diagnosing chronic kidney disease. 2

4. Sample collection: First morning void is preferred; patients should refrain from vigorous exercise for 24 hours before collection. 1, 2

Critical Pitfalls to Avoid

• Do not use 24-hour timed urine collections for routine practice—they are cumbersome, prone to collection errors, and offer no advantage over spot PCR for risk stratification. 1, 3

• Avoid testing during conditions that cause transient proteinuria: urinary tract infection, fever, marked hyperglycemia, congestive heart failure, or menstruation. 2, 4

• Do not rely on dipstick alone for diagnosis—always confirm with quantitative PCR measurement. 2

• Refrigerate samples for same-day or next-day assay; one freeze is acceptable if necessary, but avoid repeated freeze-thaw cycles. 1

Laboratory Reporting Standards

• Laboratories should report PCR as mg protein/g creatinine with a reference range of <200 mg/g. 1

• At very high proteinuria levels (PCR >500-1,000 mg/g), total protein measurement becomes more practical than albumin-specific assays. 1

• Both PCR and ACR demonstrate similar predictive value for adverse outcomes in CKD patients, with adjusted hazard ratios of 1.41 vs 1.38 for mortality and 1.96 vs 2.33 for renal replacement therapy. 3