Creatinine clearance measures the ratio between the rate of elimination of creatinine by the kidneys (through urine) and its concentration in the blood. Since creatinine is eliminated only by renal filtration, the measurement of its clearance makes it possible to evaluate the filtration rate of the kidneys. In the evaluation of clearance, the interpretation should take into account age, sex, weight, height, cardiac and renal function, and drug treatment (salicylates, cimetidine, trimethoprim, probenecid, etc.).
Creatinine clearance is prescribed when the kidney disease is suspected, before prescribing medications that involve having normal kidney function, and when renal blood flow is reduced due to heart disease.
This examination can also be requested after an initial blood test showing high blood creatinine.
The Schwartz formula makes it possible to estimate creatinine clearance up to 21 years of age. It is not valid beyond that.
Formule: Clearance = K x Taille (cm) / Créatinine.
K = 36,5 (nouvelle formule 2009),
49 (enfant < 12 ans),
53 (fille 12-21 ans),
62 (garçon 12-21 ans).
5 - 7 days: 50.6+/-5.8 mL/min.1.73m²;
1 - 2 months: 64.6+/-5.8 mL/min.1.73m²;
5 - 8 months: 87.7+/-11.9 mL/min.1.73m²;
9 - 12 months: 86.9+/-8.4 mL/min.1.73m²;
> 12 months: M: 124+/-26; F: 109+/-13.5 mL/min.1.73m².