Not medically reviewed
Urinalysis
Urine albumin-to-creatinine ratio (ACR)
Not medically reviewed · Content last updated · 1 min read ·
This is the date the draft was written, not a medical review date.
A spot-urine measure of albumin excretion, normalised to creatinine to correct for urine concentration. Persistent albuminuria is an early marker of kidney damage and of cardiovascular risk, and it is part of CKD staging.
Reference interval
| Conventional (mg/g) | SI (mg/mmol) | |
|---|---|---|
| Adults | < 30 (upper limit) mg/g | < 3.4 (upper limit) mg/mmol |
Specimen: Spot urine, preferably first morning · Conventional × 0.113 = SI
Causes of high values
Diabetic and hypertensive kidney disease, glomerulonephritis, nephrotic syndrome, chronic kidney disease. Transient rises occur with fever, urinary infection, vigorous exercise, heart failure and menstrual blood contamination.
Causes of low values
Not applicable; a low value is the normal state.
Pre-analytical and method notes
KDIGO categories are A1 below 30 mg/g (below 3 mg/mmol), A2 30 to 300 mg/g (3 to 30 mg/mmol) and A3 above 300 mg/g (above 30 mg/mmol). An abnormal result should be confirmed on two of three samples over 3 to 6 months, and low creatinine excretion (low muscle mass) can inflate the ratio. Reference intervals vary by laboratory, method and population; use the interval printed on the report.
References
- KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Disease: Improving Global Outcomes (2013) — Tier 2 (guidelines / primary literature)
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- Brenner and Rector's The Kidney. Elsevier, 11th edition (2019) — Tier 3 (textbook)
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