Urine Albumin - Creatinine Ratio

General information

Quantification of Albumin in Urine: The UACR is the ratio between two measured parameters:

• Urinary Albumin (mg/L) / Urinary Creatinine (mmol/L) = UACR in mg/mol ~ Albumin excretion in mg/day.

UACR estimates the 24-hour urinary albumin excretion. It is reported in mg/mol and closely approximates the 24-hour albumin excretion in mg/day. UACR should be measured in the first morning urine sample whenever possible. Collecting a 24-hour urine sample or other diuresis is not required.

Clinical Significance: Albuminuria (albumin in the urine) is the earliest sign of chronic kidney disease (CKD). The albumin-creatinine ratio (UACR) in a single urine sample is the recommended test for assessing and monitoring albumin excretion.

Assessment of urinary albumin excretion is mainly advised for patients with diabetes to detect and monitor early kidney damage:

• Once a year for patients with type 1 diabetes for five or more years.

• Once a year for patients with type 2 diabetes from the time of diagnosis.

• More frequent monitoring may be required for patients with changes in clinical status or after therapeutic interventions.

Other conditions where the test might be helpful include arterial hypertension, chronic heart failure, certain kidney diseases, etc.

Sample Collection, Preparation, and Manipulation: The study requires a morning urine sample (first or second). However, random urine samples are also informative. Patients should refrain from strenuous exercise 24 hours before the test. UACR may not be accurate in individuals with extremely high or low muscle mass due to variations in creatinine production.

Deviation from Normal Values: As most people know, microalbuminuria is one of the earliest indicators of diabetic nephropathy. Urinary albumin excretion is an early marker of cardiovascular morbidity and mortality and kidney function loss. Its early detection is crucial since initial kidney damage can be reversible through dietary changes (protein and salt restriction) and therapy (e.g., ACE inhibitors, angiotensin receptor blockers).

Microalbuminuria is defined as UACR ≥ 3.5 mg/mmol (women) or ≥ 2.5 mg/mmol (men):

• < 3 mg/mmol: Normal or slightly increased.

• 3–29 mg/mmol: Moderately increased.

• >30 mg/mmol: Severely increased.

If UACR exceeds the reference range:

1. Repeat the test to confirm the result.

2. Due to variability in albumin excretion, two out of three tests within a 3–6 month period should be outside normal ranges to confirm increased albumin excretion or progression of albuminuria.

Fever, acute infections, and physical exertion can elevate urinary albumin excretion, so testing is best performed outside of these conditions.

Advantages of UACR:

• Unlike test strips for albumin, UACR adjusts for variations in urine concentration.

• First morning urine is preferable as its higher concentration improves the detection of low-quantity analytes.

• Random urine samples collected during office visits are acceptable if the first morning sample isn't available.

• Collecting a 24-hour urine sample isn't necessary for routine evaluation.

Sample Collection Process: Urine is collected in a clean container (first morning sample preferred). Results are typically available by the end of the business day.