The best way to detect elevated albuminuria.

Area of Science:

• Nephrology
• Clinical Chemistry

Background:

• Assessing 24-hour urinary albumin excretion rate (UAER) is crucial for managing kidney disease.
• First morning urine specimens are often preferred over random samples for UAER assessment.
• The influence of posture and activity on albuminuria measurements needs further investigation.

Purpose of the Study:

• To investigate the impact of posture and activity on urine albumin measurements.
• To determine the best units for estimating 24-hour albuminuria.
• To compare the reliability of different albuminuria assessment methods.

Main Methods:

• A retrospective study compared 24-hour UAER with short-term (60 min supine, 90 min activity) albuminuria measurements in 124 patients.
• Urinary albumin concentration (UAC), albumin-creatinine ratio (ACR), and time-adjusted albumin excretion rate (tAER) were analyzed.
• The ability of ACR and tAER to adjust for creatininuria and collection duration was evaluated.

Main Results:

• Urinary albumin concentration (UAC) during supine collection correlated well with 24-hour UAER.
• UAC significantly increased (nearly doubled) during periods of physical activity.
• Adjustment to creatininuria (ACR) improved the correlation between short-term and 24-hour UAER, particularly during activity.

Conclusions:

• Urinary albumin concentration is significantly influenced by physical activity.
• The albumin-creatinine ratio (ACR) provides a reliable estimation of 24-hour UAER.
• ACR is recommended for practical albuminuria assessment, as it is not affected by whether the sample is supine or active.