To Estimate Creatinine Level in Serum
and Urine by Jaffe’s Reaction^18
18.1 Theory
Creatinine is a waste product derived from dehydration of creatine and is excreted by
the kidneys. It is synthesized in the kidneys, liver, and pancreas from three amino
acids–arginine, glycine, and methionine–by two enzyme-mediated reactions. After
synthesis, creatine is transported in the blood to other organs such as the muscle and
brain and phosphorylated to phosphocreatine which is a high-energy compound.
Some of the free creatine in the muscle is spontaneously converted to creatinine
(anhydride of creatine). Creatine and creatine phosphate constitute about 400 mg/
100 mg of fresh muscle. Both compounds are converted spontaneously to creatinine
at rate of 1–2% (Fig.18.1).
18.2 Specimen Requirements
Serum or plasma (fluoride or heparin) is stable for 24 h if refrigerated.
Urine: Collect 24 h urine sample. The urine should be kept in cool place (stable up
to 4 days if refrigerated). Dilute urine sample 1:10 before use.
#Springer Nature Singapore Pte Ltd. 2018
V. Kumar, K. D. Gill,Basic Concepts in Clinical Biochemistry: A Practical Guide,
https://doi.org/10.1007/978-981-10-8186-6_18
75