Microalbuminuria

This describes pathological albuminuria in the 30-200 mg/litre range which is not detectable by qualitive chemical dip sticks.

• Microalbuminuria is defined as:
  • albumin:creatinine ratio >2.5mg/mmol (men) or >3.5mg/mmol (women) or albumin concentration >20mg/l (1)
    
    
• Proteinuria is defined as:
  • albumin:creatinine ratio >30mg/mmol or albumin concentration >200mg/l (1)

Albumin excretion varies with respect to factors such as:

• time of day - overnight rates being lower
• exercise - excretion increased
• disease such as hypertension - excretion rate increased in some patients

Some examples of causes of microalbuminuria are listed.

Notes:

• the diagnosis of microalbuminuria cannot be made in the presence of an acute metabolic crisis. As far as is practicable, the best possible metabolic control of diabetes should be achieved before investigating patients for microalbuminuria. Patients should not be screened during intercurrent illness (3)
• the Renal Association note that (4):
  • use of early morning urines to measure albumin creatinine ratio (ACR) gives a more accurate estimate of 24h urine albumin, though random samples have acceptable performance
  • additionally, early morning urines allow the exclusion of orthostatic proteinuria. In orthostatic proteinuria significant urinary protein is excreted when erect, but when recumbent the urinary protein is completely normal. This usually occurs in young adults, and has no long-term consequences
  • for the diagnosis of microalbuminuria 2 abnormal results from 3 specimens are required

Reference:

1. MeReC Briefing 2004;26:1-8.
2. Gosling P. Microalbuminuria: a marker for systemic disease, BJHM 1995; 54(6): 285-90.
3. The Renal Association (May 2006).UK CKD Guidelines
4. UK Renal Association (2011). Detection, Monitoring and Care of Patients with CKD