Butani L, Polinsky M, Kaiser B, Kropp C, Baluarte HJ
Impact of dietary protein source on serum creatinine
concentration as determined by a specific enzyme assay
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1578 1996
The effect of dietary protein intake on the measurement of serum urea
nitrogen levels is recognized as a significant source of inaccuracy in the
interpretation of this parameter of renal function. The effect of dietary
protein intake on the measurement of serum creatinine levels is also known
to be a source of inaccuracies, though generally it is thought to be a
relatively inconsequential problem.
Studies utilizing the alkaline picrate method of Jaffe to measure
creatinine have shown a marked decrease in the measured serum creatinine
level when protein intake was reduced.
The current abstract evaluated a different method of creatinine
measurement, based on a specific enzymatic assay, to evaluate its
vulnerability to the effect of dietary protein. A dietary protein load was
given to 5 healthy volunteers before and after a meal containing 300 gm of
cooked beef protein. There was a significant 98.5% increase in the
measured creatinine following the protein load. This experiment was
repeated with the substitution of cooked turkey or ham protein. This
resulted, respectively, in a 16.2% and 10.9% increase in measured
creatinine.
Comment: It appears that the increase in measured creatinine
following protein loading is not limited to the Jaffe method. The Jaffe,
or total chromagen method, is known to measure other non-creatinine
chromagens, e.g. ascorbic and uric acids. Whether the method used in this
study has similar vulnerabilities is unknown, though this seems unlikely.
It is claimed that cooking converts the creatine in muscle to creatinine
which is rapidly absorbed following ingestion. Unfortunately, the effect
of ingesting raw meat on the serum creatinine was not investigated in the
current study.
(Greg Cowell, M.D., University of Illinois at Chicago)
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Am Soc Nephrol
Assessing renal function :
Creatinine clearance