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The urinary albumin:creatinine ratio is a useful measure of renal function
used in diabetic renal disease.
The urinary albumin:creatinine ratio is measured using the first morning urine
sample where practicable.
Microalbuminuria is defined as: albumin:creatinine ratio >2.5mg/mmol (men)
or >3.5mg/mmol (women) or albumin concentration >20mg/l.
Proteinuria is defined as: albumin:creatinine ratio >30mg/mmol or albumin
concentration >200mg/l.
Notes:
- NICE suggest that (2):
- all people with diabetes, and people without diabetes with a GFR
less than 60 ml/min/1.73 m^2, should have their urinary albumin/protein
excretion quantified. The first abnormal result should be confirmed on
an early morning sample (if not previously obtained)
- quantify by laboratory testing the urinary albumin/protein excretion
of people with an eGFR 60 ml/min/1.73 m2 or more if there is a strong
suspicion of CKD
- for the initial detection of proteinuria, if the albumin:creatinine
ratio (ACR) is 30 mg/mmol or more (this is approximately equivalent to
protein: creatinine ratio (PCR) 50 mg/mmol or more, or a urinary protein
excretion 0.5 g/24 h or more) and less than 70 mg/mmol (approximately
equivalent to PCR less than 100 mg/mmol, or urinary protein excretion
less than 1 g/24 h) this should be confirmed by a subsequent early morning
sample
- If the initial ACR is 70 mg/mmol or more, or the PCR 100 mg/mmol
or more, a repeat sample need not be tested
- in people without diabetes consider clinically significant proteinuria
to be present when the ACR is 30 mg/mmol or more (this is approximately
equivalent to PCR 50 mg/mmol or more, or a urinary protein excretion 0.5
g/24 h or more)
- in people with diabetes consider microalbuminuria (ACR more than 2.5
mg/mmol in men and ACR more than 3.5 mg/mmol in women) to be clinically
significant
- do not use reagent strips to identify proteinuria unless they are capable
of specifically measuring albumin at low concentrations and expressing
the result as an ACR
- to detect and identify proteinuria, use urine ACR in preference, as
it has greater sensitivity than PCR for low levels of proteinuria. For
quantification and monitoring of proteinuria, PCR can be used as an alternative.
ACR is the recommended method for people with diabetes
- the Renal Association note that (3):
- 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
Reference:
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