Regarding a recent enquiry on creatine interference with routine creatinine
assays.
We have found no interference from creatine with the Roche Creatinine Plus
enzymatic creatinine assay up to 2000 umol/L creatine ( Modular P Unit ).
The Modular Jaffe assay (rate blank with compensation) has a positive
interference of approximately +16 umol/L for this extremely high
concentration of creatine, which decreases proportionally at lower
concentrations.
I have also seen data that indicates that creatine concentations of 200
umol/L do not interfere with the Beckman Coulter Dx C800 assay.
Typical concentrations of creatine in serum are 13 -> 71 umol/L ( approx 0.2
-> 0.9 mg/dL ). Molecular weight 131.14 Daltons.
It may increase to 150 -> 400 umol/L ( 2.0 -> 5.2 mg/dL) or higher in
critically ill patients.
Refs. Skurup Anne et al. New creatinine sensor for POCT testing of
creatinine meets NKDEP program guidelines. Clin Chem Lab Med 2008; 46(1)
: 3-8.
Wyss Markus et al. Physiological Reviews. Creatine and
creatinine metabolism 2000; 80(3): 1107- 1213 ( an excellent review ).
Michael Peake
Flinders Medical Centre
Adelaide
Souh Australia.
PS Sally, what Jaffe creatinine assay are you using in your laboratory?
_____
From: Clinical biochemistry discussion list
[mailto:[log in to unmask]] On Behalf Of Margaret Sinclair
Sent: Tuesday, 29 September 2009 12:15 AM
To: [log in to unmask]
Subject: FW: Creatine interference in the creatinine method
We have a patient taking body-building supplements containing creatine which
we believe is giving us a positive interference on our Jaffe method.
Does anyone run an enzymatic creatinine method that removes endogenous
creatine such as the Cambridge Life Science method?
Many thanks
Sally
Sally Slack
Senior Clinical Biochemist
Department of Clinical Biochemistry
York Hospital
Wigginton Road
York
YO31 8HE
01904 725599
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