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How to Assess Proteinuria
🧪 How to Assess Proteinuria — 30 Key Points (KDIGO-Aligned)
- First step: quantify proteinuria using spot urine ACR (albumin-creatinine ratio).
- ACR is preferred over PCR because it specifically measures albumin.
- Early-morning urine sample gives the most reliable ACR.
- Proteinuria = total protein, albuminuria = albumin only — KDIGO uses albuminuria categories.
- A1 (normal-mild): ACR <30 mg/g (<3 mg/mmol).
- A2 (moderate): ACR 30–300 mg/g (3–30 mg/mmol).
- A3 (severe): ACR >300 mg/g (>30 mg/mmol).
- Dipstick is NOT reliable for quantifying proteinuria; detects albumin only, not light chains.
- Confirm persistent proteinuria: repeat ACR ≥2 times over 3–6 months.
- 24-hour urine protein is not preferred but used when precise measurement is needed.
- Spot urine PCR estimates total protein loss (mg/g).
- Significant proteinuria: PCR >150–200 mg/g.
- Nephrotic-range proteinuria: PCR >3500 mg/day or urine protein >3.5 g/day.
- Nephrotic-range ACR: >2200 mg/g (~>250 mg/mmol).
- Orthostatic proteinuria: check split daytime vs overnight urine samples.
- Transient proteinuria occurs with fever, exercise, dehydration — repeat testing needed.
- Microalbuminuria term is outdated; KDIGO calls it A2 albuminuria.
- Albuminuria is a CV risk marker, not just kidney damage.
- Proteinuria should be assessed at diagnosis of hypertension, diabetes, CKD, and annually.
- Proteinuria progression (>30% rise from baseline) predicts CKD progression.
- Persistent A2–A3 albuminuria = CKD even if eGFR >60.
- ACR variability: interpret trends, not single values.
- Check for hematuria along with proteinuria to stratify glomerular disease.
- Rule out UTI → false-positive proteinuria on strip.
- Foamy urine is not a reliable clinical indicator of proteinuria.
- DKD diagnosis relies heavily on persistent A2+ albuminuria.
- Albuminuria reduction ≥30% predicts kidney/CV benefit of therapies (ACEI/ARB/SGLT2i).
- ACEI/ARB can transiently raise creatinine but reduce proteinuria long-term.
- Urine electrophoresis is required when light-chain disease is suspected.
- Monitor ACR every 3–6 months in moderate-to-severe albuminuria or on RAAS blockers/SGLT2i.
