Test Details
Urinary Albumin/Creatinine Ratio
A recommended method to identify albuminuria, an increased excretion of urinary albumin and a marker of kidney damage.
Normal individuals excrete very small amounts of protein in the urine. Albumin is the most common type of protein in the blood and the urine. All patients with chronic kidney disease (CKD) should be screened for albuminuria. Persistent increased protein in the urine is one of the principal markers of kidney damage, acting as an early and sensitive marker in many types of kidney disease.
Methodology
Albumin- Immunoturbidimetric
Creatinine- Enzymatic
The Albumin Creatinine Ratio is calculated as follows:
Albumin (mg/L) X 100 = Albumin (mg)/Creatinine (g)
Creatinine (mg/dL)
Patient Preparation
None
Preferred Specimen
10 mL of urine collected in a Yellow Top
Transport Temperature
Refrigerated (ship on frozen cold packs)
Stability
Refrigerated 2-8C: 2 days
Note: Stability based off creatinine stability (most stringent)
Lab Values
Urinary Albumin/Creatinine Ratio
Normal: <30 mg/g
High: >30 mg/g
Clinical Significance
Urinary Albumin/Creatinine Ratio
A routine dipstick is not sensitive enough to detect small amounts of urinary protein. Therefore, it is recommended that screening in adults at risk for cardiovascular disease (CVD) and CKD be done by testing for albuminuria. According to the American Kidney Foundation the urinary albumin-to-creatinine ratio (ACR) is the method of choice to detect elevated urinary protein. The recommended method to evaluate albuminuria is to measure urinary ACR in a spot urine sample. ACR is calculated by dividing albumin concentration in milligrams by creatinine concentration in grams. Although the 24-hour collection has been the “gold standard,” alternative methods for detecting protein excretion such as urinary albumin-to-creatinine ratio (ACR) correct for variations in urinary concentration due to hydration, as well as provide more convenience than timed urine collections. The spot urine specimen has been shown to correlate well with 24-hour collections.
Moderately increased albuminuria, historically known as microalbuminuria, (ACR 30-300 mg/g) refers to albumin excretion above the normal range, but below the level of detection by tests for total protein. Severely increased albuminuria, historically known as macroalbuminuria, (ACR >300) refers to a higher elevation of albumin associated with progressive decline in estimated glomerular filtration rate (eGFR).
Treatment Options
Urinary Albumin/Creatinine Ratio
A value of < 30 mg/g has been classified as normal or only mildly increased, a value of 30-300 mg/g as moderately increased, and a value > 300 mg/g as severely increased by the American Kidney Foundation. Major risk factors for CKD include diabetes and hypertension. The careful treatment of these conditions with lifestyle modification and various medications to maintain a HbA1c of < 7.0% and a blood pressure of < 130/90 mmHg may slow or prevent progression of CKD as assessed by the ACR, as well as estimated glomerular filtration as assessed with creatinine and/or cystatin C.
