But the OCD-Vitros (creatinine) datasheet says that endogenous creatine is
oxidised during the initial incubation. Creatine is listed in
the 'limitations of the procedure' section indicating that results will be
flagged 'DP' or, if not flagged, the bias will be <10% at 133 umol/L, or
<2% at 1237 umol/L.
Not great, but if I've got chromogenic junk in my serum I'd rather have my
creatinine measured by a hydrolase method than by Jaffe. Unfortunately,
one can't plug an OCD creatinine (or BCP albumin) into the Andrew Levey et
al GFR formula (AIM, 1999, 130:461-470) since they used an Astra 8 (kinetic
alkaline picrate, BCG).
By the way, does posture affect GFR to the extent implicated by the albumin
term in the Levey predictive equation ('though [alb. g/dL]^0.318 is not a
particularly large effect, I suppose)?
Godfrey Gillett
Sheffield
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From: Mike Collins[SMTP:[log in to unmask]]
Reply To: Mike Collins
Sent: 10 January 2002 08:42
To: [log in to unmask]
Subject: Re: Creatinine clearance test using 6 hours timed urine
collection
snipped
An increasing number of people are also taking creatine
supplements. Some methods (particularly Vitros) will detect
this as creatinine. Perhaps using Cystatin-C is a safer
measure of GFR.
Mike Collins
snipped
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