NICE have decided to adopt the recommendations of NKF-KDOQI regarding
quantifing Proteinuria in terms of ACR rather than those of UK CKD and
Wales Renal NSF which recommend PCR measurement in non-diabetic patients.
The proposeed NICE reccommendations are
R12 In people without diabetes therapeutically significant proteinuria
should be considered to be present when the ACR exceeds 30 mg/mmol (this is
approximately equivalent to 0.5 g total protein/24hrs). In people with
diabetes microalbuminuria is considered significant, and is defined as ACR
¡Ý 2.5 mg/mmol in men and ACR ¡Ý 3.5 mg/mmol in women.
R13 An albumin:creatinine ratio (ACR) should normally be used to quantify
proteinuria.
R14 All people with diabetes, and people without diabetes with a GFR<60
ml/min/1.73m2, should have their urinary albumin excretion quantified by an
ACR. The first abnormal result should be confirmed on an early morning
sample (if not previously obtained).
R15 Those people with a GFR greater than or equal to 60 ml/min/1.73m2
should have their urinary albumin/protein excretion quantified by
laboratory testing if there is a strong suspicion of CKD.
They are advocating measuring ACRs in any one where there is a suspicion of
CKD, diabetic or non-diabetic to confrim proteinuria. Surely if the
proposed cutoff to signifiy proteinuria is an ACR >30mg/mmol then a PCR
>50mg/mmol will surfice or in the majority of cases a positive protein
dipstick.
We currently measure a urine protein on all ACR requests and don't measure
the albumin if the protein is above a certain theshold. This may no longer
be a viable approach when the guidelines are published and there is no
accurate way of interchanging PCR and ACR results.
2 years on from the implementation of eGFR has anyone audited lab policies
regarding ACR and PCR requests, and how eGFRs are calculated and reported.
The draft guidelines reflect those of UK CKD and SIGN in many areas but the
increase in the measurement of ACR will certainly impact on lab workload
and budget.
The use of terms microalbumiuria and macroalbuminuria still confuse some
GPs and using albuminuria to quanitify proteinuria won't help.
The guidelines even recommend the use of a specific analytical method:
"3.4.5.4 From a CKD perspective the amount of albuminuria was considered the
most relevant measurement and has the advantage that the amount of
albumin can be accurately measured if an enzymatic assay is used."
As far as I'm aware an enzymatic method for Creatinine is more accurate but
urine albumin is measured by immunoturbidimetry, nephelometry, or ELISA.
Regards
Richard
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