Method(s): LC-MS/MS (1).
Performance of the assay
Lower limit of detection (LOD): 0.25 µmol/L.
Within-day CV: 3-5 %; between-day CV: 2-6 %.
Creatinine measured by LC-MS/MS is about 10 % lower than values obtained with a creatinine iminohydrolase procedure. A linear regression (n=500) with values obtain by LC-MS/MS as dependent variable gives a B (SE) of 0.783 (0.015) and a constant (SE) of 8.58 (1.173).
The difference may be related to the higher specificity of and less interference for the LC-MS/MS method.
A renal function test, providing an approximation of glomerular filtration.
Specimen, collection and processing
Patient/subject: Creatinine concentration is unaffected by most diets.
Matrix: Plasma and serum.
Volume: Minimum volume is 50 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: The blood sample must be centrifuged and the plasma/serum fraction put on ice, and frozen. Creatinine is stable.
Transportation; for general instruction on transportation, click here.
Frozen, on dry ice.
Reported values, interpretation
Reported values: Men, 55-90 µmol/L; women, 45-80 µmol/L; children, (< 16 years), 25-65 µmol/L.
Intraclass correlation coefficient (ICC) :0.77.
1. Midttun, O., Kvalheim, G., and Ueland, P.M. (2013). High-throughput, low-volume, multianalyte quantification of plasma metabolites related to one-carbon metabolism using HPLC-MS/MS. Anal Bioanal Chem 405, 2009-017.