title: Candidate reference method for determining serum creatinine by isocratic HPLC: validation with isotope dilution gas chromatography-mass spectrometry and application for accuracy assessment of routine test kits.
abstract: We present a candidate Reference Method for determining creatinine in serum, based on isocratic HPLC. The chromatographic column, with alkaline-treated aluminum oxide as stationary phase, is eluted with an equivolume mixture of methanol/acetonitrile containing 70 mL/L aqueous NaOH (10 mmol/L), and ultraviolet absorbance is detected at 240 nm. We investigated the ruggedness of the method and validated its performance with isotope dilution gas chromatography-mass spectrometry (ID GC-MS) for a set of 22 patients' sera and 10 commercially available lyophilized control materials. The mean deviation from ID GC-MS was +0.1% (range, -2.2% to +2.2%). The between-day CV, calculated from six independent measurements performed on three different days, was 0.9% (range 0.2% to 1.9%); the within-run CV was 0.8%. The total error of the method was < 3%. These performance characteristics make the method suitable for target-setting of quality-control materials and accuracy assessment of routine test kits. For the latter application, done with split-sample measurements of a panel of 83 patients' specimens, we used the Boehringer Mannheim enzymatic creatinine PAP test on the Hitachi 911, the Kodak Ektachem single-slide enzymatic creatinine test on the Ektachem 700, the Merck Jaffé kinetic assay on the Mega analyzer, and the Roche Jaffé kinetic test on the Cobas Mira.
authors.affiliation: Laboratoria voor Medische Biochemie en voor Klinische Analyse, University of Ghent, Belgium.
authors.forename: L M
authors.initials: LM
authors.lastname: Thienpont
authors.forename: K G
authors.initials: KG
authors.lastname: Van Landuyt
authors.forename: D
authors.initials: D
authors.lastname: Stöckl
authors.forename: A P
authors.initials: AP
authors.lastname: De Leenheer
mesh_terms: D000537:Aluminum Oxide; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003404:Creatinine / Q000097:blood*; D005612:Freeze Drying; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007201:Indicator Dilution Techniques; D011786:Quality Control; D011933:Reagent Kits, Diagnostic / Q000592:standards / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D011933:Reagent Kits, Diagnostic; D003404:Creatinine; D000537:Aluminum Oxide