Urine albumin-to-creatinine ratio (ACR)
1 day The urinary albumin-to-creatinine ratio (ACR – Albumin-to-Creatinine Ratio) is a laboratory test used to assess urinary albumin excretion and to enable early detection of kidney damage.
Albumin is the main plasma protein, which is normally retained by the glomerular filtration barrier and is present in urine only in minimal amounts. An increased urinary excretion of albumin indicates increased glomerular membrane permeability and may represent an early sign of kidney damage.
Creatinine, a product of muscle metabolism, is continuously excreted by the kidneys. Its urinary concentration allows correction for variations in urine dilution. The ACR reflects the amount of albumin relative to creatinine, providing a reliable estimate of albuminuria from a single urine sample, without the need for 24-hour urine collection.
ACR determination plays an important role in detecting microalbuminuria, monitoring chronic kidney disease, and assessing cardiovascular risk.
Indications
- diabetes mellitus (annual screening for diabetic nephropathy)
- arterial hypertension
- suspected chronic kidney disease
- monitoring of patients with known renal disease
- metabolic syndrome, obesity
- family history of kidney disease
- systemic diseases with possible renal involvement (e.g. autoimmune diseases)
Procedure
The test is performed using a single spot urine sample, preferably the first morning urine. The sample is collected in a sterile container, following proper hygiene rules to avoid contamination.
The analysis measures urinary albumin and creatinine concentrations and calculates the ACR ratio, which reflects the degree of glomerular filtration impairment.
Preparation:
Before the test:
- It is recommended to use the first morning urine or a sample collected at least 4 hours after the last urination
- Maintain normal hydration the day before the test, avoiding excessive fluid intake
- Avoid intense physical activity for 24 hours prior to sample collection
- The examination may be postponed in case of fever, acute infections, urinary tract infection, hematuria, menstrual bleeding, as well as acute disturbances of blood pressure or glucose levels
- At the physician’s discretion, avoidance of meat consumption for 24 hours before the test may be recommended
During collection:
- The “midstream urine” technique is used to obtain the sample
- Proper hand and external genital hygiene is performed
- The first portion of urine is voided into the toilet without collection
- 30–60 ml of urine is collected into a sterile container, avoiding contact with the inner surface
- The container is tightly closed and submitted to the laboratory according to instructions
General recommendations:
- avoid alcohol consumption for 24 hours before collection
- avoid smoking for several hours before the test
- inform the physician about any medications currently being taken
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