title: An automated turbulent flow liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) method for quantitation of serum creatinine.
abstract: BACKGROUND
  When creatinine concentrations determined by routine clinical assays are in question, reference methods can aid investigation. Currently available reference methods are significantly labor-intensive, which prevents implementation in a routine clinical laboratory.
  
  
  METHODS
  Creatinine D-3 internal standard was added to serum prior to chromatographic separation. A TurboFlow Cyclone MCX column was used for online solid phase extraction (SPE) to remove large biomolecules such as proteins, carbohydrates and phospholipids from the serum specimen. Creatinine and creatinine D-3 were then eluted onto a Hypercarb (porous graphitic carbon) column for separation. Analytes were detected using electrospray ionization tandem mass spectrometry and measured by monitoring parent ions of m/z 114 and 117, respectively.
  
  
  RESULTS
  Total precision at multiple levels was found to be less than 6% (1.0-7.5 mg/dl). Limit of detection (LOD) was 0.05 mg/dl and limit of quantitation (LOQ) was 0.20 mg/dl. Average recovery was 107.5% (0.37-5.95 mg/dl). Analysis of standard reference materials from The National Institute of Standards and Technology (NIST) confirmed accuracy of the method. No significant difference was found between the liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) method and the Roche Creatinine Plus enzymatic assay.
  
  
  CONCLUSIONS
  The automated turbulent flow LC-IDMS method for quantitation of serum creatinine is accurate, robust, and easy to perform and may serve as a quick and inexpensive alternative to current creatinine reference methods.
authors.affiliation: John Hopkins Hospital, Baltimore, MD, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Harlan
authors.forename: William
authors.initials: W
authors.lastname: Clarke
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Di Bussolo
authors.forename: Marta
authors.initials: M
authors.lastname: Kozak
authors.forename: Joely
authors.initials: J
authors.lastname: Straseski
authors.forename: Danni Li
authors.initials: DL
authors.lastname: Meany
mesh_terms: D002853:Chromatography, Liquid / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D003404:Creatinine / Q000097:blood*; D003903:Deuterium; D006801:Humans; D011865:Radioisotope Dilution Technique; D012015:Reference Standards; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation* / Q000379:methods / Q000592:standards
chemical_list: D003903:Deuterium; D003404:Creatinine