Serum creatinine and estimated glomerular filtration rate

Published Date: 19th July 2016

Publication Authors: Hardy KJ, O'Brien S

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OBJECTIVE 

Fasting is not routinely recommended for renal function tests, despite the known effects of cooked meat on creatinine. We therefore studied variation in creatinine and estimate glomerular filtration rate (eGFR) following a standardised cooked meat meal in 80 subjects: healthy volunteers, diabetes patients with chronic kidney disease (CKD) stages 1 & 2, 3A, 3B and 4 (n=16/group).

RESEARCH DESIGN AND METHODS 

The interventions were a standardised cooked meat and a non-meat meal, each providing approximately 54g protein, together with 250 mls of water, on separate days. Fasting and post-prandial blood samples at 1, 2, and 4 hours were drawn for creatinine measurement using kinetic alkaline picrate assay on an Olympus AU640 analyser. The modified 4-variable MDRD equation traceable to isotope dilution mass spectrometry creatinine was used to calculate eGFR.

RESULTS 

Consumption of a standardised cooked meat meal significantly increased serum creatinine and resulted in significant fall in eGFR in all stages of CKD studied; 6 of 16 CKD 3a patients were misclassified as CKD 3b. This effect of cooked meat on serum creatinine disappears after 12 hours of fasting in all study participants.

CONCLUSIONS 

Creatine in meat is converted to creatinine on cooking which is absorbed causing significant increases in serum creatinine. This could impact management as threshold for commencing and withdrawing certain medications and expensive investigations is defined by eGFR. eGFR calculated using fasting serum creatinine would be a better reflection of kidney function in these patients.

Nair, S; O'Brien, SV; Hardy, KJ et al. (2014).  Effect of a cooked meat meal on serum creatinine and estimated glomerular filtration rate in diabetes-related kidney disease . Diabetes Care. 37 (2), 483-87

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