How is a Urine Albumin-to-Creatinine Ratio (UACR) test taken?

How to Collect a UACR Sample

The preferred method for collecting a urine albumin-to-creatinine ratio (UACR) is a first morning void urine sample, which should be used for initial testing and confirmation of albuminuria. 1

Sample Collection Method

Preferred Collection Approach

• Collect a first morning void urine sample as the gold standard for UACR measurement, as this minimizes variability and provides the most reliable results 1
• A random spot urine sample is acceptable if a first morning void is difficult to obtain, though timing should be consistent across collections 1
• No timed or 24-hour urine collections are necessary for routine UACR testing—these are cumbersome, error-prone, and add no clinical value over spot samples 1

Pre-Collection Requirements

When collecting a random sample (if first morning void is not feasible):

• The patient should be well hydrated 1
• No food intake within the preceding 2 hours 1
• No exercise prior to collection 1
• Collect at the same time of day for serial measurements to minimize variability 1

Confirmation Protocol

Initial Positive Results

• If the initial UACR is ≥30 mg/g (≥3 mg/mmol), confirm with a subsequent first morning void sample 1
• Two of three specimens collected within a 3-6 month period should be abnormal to establish persistent albuminuria 1
• This confirmation step is critical because single measurements can be affected by transient factors 1

Point-of-Care Testing Considerations

• Point-of-care testing (POCT) devices may be used where laboratory access is limited, but they must meet quality standards 1
• Semiquantitative dipstick tests should detect >85% of individuals with moderately increased albuminuria to be clinically useful 1
• Any positive semiquantitative test must be confirmed by quantitative laboratory measurement expressed as a ratio to urine creatinine 1

Common Pitfalls to Avoid

Factors That Invalidate Results

Several conditions can falsely affect UACR measurements and should be avoided:

• Vigorous exercise within 24 hours of collection 2
• Fever or acute illness at time of collection 2
• Dehydration or highly concentrated urine 2
• Menstruation or urinary tract infection 1

Technical Considerations

• Do not use standard protein dipsticks for albuminuria screening—they lack sensitivity at albumin concentrations of 20-50 mg/L and cannot detect microalbuminuria 1
• Use albumin-specific dipsticks or quantitative laboratory methods that measure both albumin and creatinine to calculate the ratio 1
• Results should be interpreted cautiously when urinary creatinine is below 2 mmol/L, as ratios may appear falsely elevated 3

Laboratory Analysis Timing

• Samples should be analyzed on the same day as collection when possible 4
• If delayed analysis is necessary, samples can be stored at 4°C for 24-48 hours without significant impact on accuracy 4
• Avoid storage beyond 48 hours at 4°C or prolonged freezing (3-9 months at -80°C), as this can systematically overestimate ACR values 4