Creatinine | Laboratory research

Creatinine Is Creatine Anhydride (Methylguanidylacetic acid) and creatine elimination form; Creatine is synthesized in the liver and 98% of it is absorbed by the muscles, where it is phosphorylated, in this form it plays an important role in maintaining muscle energy. When this muscle energy is needed for metabolic processes, phosphocreatine is broken down into creatinine, hence creatinine is formed in muscle tissue. In men, 1,5% of the creatine supply is converted to creatinine daily. Creatine from food (especially meat) increases the supply of creatine and creatinine. Decreased protein intake leads to a decrease in creatine precursors, amino acids - arginine and glycine - in the body, which in turn leads to a decrease in the amount of creatinine.

Serum creatinine is a more specific and sensitive indicator of renal function than urea. However, in chronic kidney disease, it is useful to determine both creatinine and serum urea (BUN (Blood Urea Nitrogen) - with the urea nitrogen parameter), as the BUN / creatinine ratio (norm - 10-20) provides more information about renal function.

How to prepare for the test?

• It is advisable to do the test on empty stomach .
• Tell your doctor what medications you are taking (especially cimetidine, nonsteroidal anti-inflammatory drugs (eg aspirin, ibuprofen), chemotherapy, cephalosporins, etc.) before the test.
• It is not advisable to eat more than 200 g of meat, especially beef, for at least 24 hours before testing, as this may temporarily increase blood creatinine levels. You should also avoid strenuous exercise for at least 48 hours before testing.
• Alcohol, smoking and physical activity should be excluded for 12 hours before the study.
• In the morning, on the day of taking blood, you can get water.

Higher creatinine levels are found in men and people with large muscle mass.

The same creatinine concentration in young and old does not mean the same glomerular filtration rate (creatinine clearance (excretion) decreases in the elderly, but creatinine production also decreases)

Under conditions of impaired renal perfusion, the increase in serum creatinine occurs more slowly than in urea.

Because a 1.0% loss in renal function is required to increase creatinine levels from 2.0 to 50 mg / dL, serum creatinine cannot be considered a sensitive indicator of mild to moderate renal insufficiency.

Serum creatinine levels can be used to estimate glomerular filtration rate only at steady state when the rate of creatinine synthesis equals elimination. To determine this condition it is necessary to determine both determinants (rate of synthesis, elimination) every 24 hours; A difference of more than 10% may indicate that there is no such state of equilibrium.

In case of impaired renal function, The rate of glomerular filtration is overestimated by serum creatinine, as creatinine clearance is not only due to glomerular filtration but also through tubular secretion and is also excreted by the intestinal mucosa and appears to be metabolized by metabolites.

A diet rich in meat May increase serum creatinine content (15-30% of daily creatinine excreted comes from food).