What should be the level of random urine microalbumin?

Normal Random Urine Microalbumin Levels and Diagnostic Thresholds

Normal random urine microalbumin should be less than 30 mg/g creatinine, with microalbuminuria defined as 30-299 mg/g creatinine and macroalbuminuria as ≥300 mg/g creatinine. 1

Diagnostic Thresholds for Albuminuria

• Normal albuminuria: <30 mg/g creatinine on spot collection, <30 mg/24h on 24-hour collection, or <20 μg/min on timed collection 1
• Microalbuminuria: 30-299 mg/g creatinine on spot collection, 30-299 mg/24h on 24-hour collection, or 20-199 μg/min on timed collection 1
• Macroalbuminuria: ≥300 mg/g creatinine on spot collection, ≥300 mg/24h on 24-hour collection, or ≥200 μg/min on timed collection 1

Collection Methods and Recommendations

• Random spot urine albumin-to-creatinine ratio is the preferred and most practical screening method for clinical settings 1
• First morning void samples are preferred to minimize effects of orthostatic proteinuria, particularly important in children and adolescents 1, 2
• Diagnosis requires confirmation with 2 out of 3 abnormal specimens collected within a 3-6 month period due to significant day-to-day variability 1
• Standard dipstick tests are inadequate for detecting microalbuminuria; specific immunoassays for albumin are required 1, 2

Factors Affecting Urinary Albumin Excretion

• Exercise within 24 hours before collection can cause temporary elevation in albumin excretion 1, 2
• Acute infections, fever, and urinary tract infections can lead to transient microalbuminuria 2, 3
• Congestive heart failure can increase venous pressure resulting in microalbuminuria 2, 3
• Marked hyperglycemia can cause transient microalbuminuria even without established diabetic nephropathy 1, 2
• Marked hypertension can cause pressure-related albumin leakage 1, 2
• Hematuria and pyuria can cause false elevations in measured albumin 2, 3

Clinical Significance and Screening Recommendations

• Microalbuminuria is an early marker of diabetic kidney disease and predicts progression to overt nephropathy 4, 5
• Microalbuminuria is an independent predictor of cardiovascular morbidity and mortality in both diabetic and non-diabetic patients 6, 7
• Screening for microalbuminuria should begin at diagnosis for type 2 diabetes and after 5 years of disease duration for type 1 diabetes 1
• Annual screening is recommended for patients with diabetes, hypertension, or family history of chronic kidney disease 1

Technical Considerations for Accurate Measurement

• Laboratories should report albuminuria as milligrams of albumin per gram of creatinine 1
• Refrigerate urine samples for assay the same or next day; one freeze is acceptable if necessary 1
• For very high levels of proteinuria (spot urine total protein to creatinine ratio 500-1,000 mg/g), measurement of total protein instead of albumin is acceptable 1
• Consider sex differences in creatinine excretion; multiply the concentration in men by 0.68 to provide a sex-independent reference range 1, 2

Common Pitfalls to Avoid

• Relying on a single measurement can be misleading due to high variability in urinary albumin excretion 1, 2
• Failing to adjust for creatinine can lead to errors from variations in urine concentration 2, 8
• Not accounting for transient causes of microalbuminuria can lead to misdiagnosis 2, 3
• Using standard dipstick tests instead of specific microalbumin assays will miss microalbuminuria 1, 4