Diabetic nephropathy can be classified into normal, microalbuminuria, macroproteinuria and endstage renal disease, according to the amount of albumin excreted. Albumin excretion should be measured on 3-4 samples before persistent microabuminuria is declared to be present as there is often a diurnal variation in excretion of upto 40%. It should also be noted that there is a relationship between the blood pressure and level of proteinuria.
STAGE
Normal
Micro
Macro
End Stage Renal Disease (ESRD)
albumin excretion (mg/l)
<20
20-200
>200
>1000
blood pressure
120/75
130/85
145/95
160/100
GFR (ml/min)
>110
>110
<100
<30
Patients with microalbuminuria often have associated problems of hypertension, left ventricular hypertrophy and insulin resistance.
Patients that develop frank proteinuria are a group that have more problems and appear to have more aggressive disease and particularly have problems with macrovascular disease with an increased mortality.
NICE suggest (1):
clinicians should use urine albumin:creatinine ratio (ACR) in preference to protein:creatinine ration (PCR) in order to detect proteinuria
ACR has greater sensitivity than protein:creatinine ratio (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
for the initial detection of proteinuria, if the ACR is between 3 mg/mmol and 70 mg/mmol, this should be confirmed by a subsequent early morning sample. If the initial ACR is 70 mg/mmol or more, a repeat sample need not be tested
regard a confirmed ACR of 3 mg/mmol or more as clinically important proteinuria
quantify urinary albumin or urinary protein loss for:
people with diabetes
people without diabetes with a GFR of less than 60 ml/min/1.73 m^2
NICE suggested a classification of CKD incorporating GFR and ACR (1)
ACR (albumin creatinine ratio) category
ACR (mg/mmol)
A1
<3
A2
3-30*
A3
>30**
* Relative to young adult level
** Including nephrotic syndrome (ACR usually >220 mg/mmol)
CKD is classified according to estimated GFR (eGFR) and albumin:creatinine ratio (ACR), using 'G' to denote the GFR category (G1-G5, which have the same GFR thresholds as the CKD stages 1-5 recommended previously) and 'A' for the ACR category (A1-A3), for example:
a person with an eGFR of 25 ml/min/1.73 m2 and an ACR of 15 mg/mmol has CKD G4A2.
a person with an eGFR of 50 ml/min/1.73 m2 and an ACR of 35 mg/mmol has CKD G3aA3
an eGFR of less than 15 ml/min/1.73 m2 (GFR category G5) is referred to as kidney failure
it is noted that:
increased ACR is associated with increased risk of adverse outcomes
decreased GFR is associated with increased risk of adverse outcomes
increased ACR and decreased GFR in combination multiply the risk of adverse outcomes
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