title: CYP1A2 phenotyping in dried blood spots and microvolumes of whole blood and plasma.
abstract: BACKGROUND
  Phenotyping, using caffeine as probe substrate, is a proper method to assess CYP1A2 activity. We evaluated the utility of dried blood spots (DBS) for CYP1A2 phenotyping.
  
  
  RESULTS
  LC-MS/MS methods were developed and validated for quantitation of caffeine and its metabolite paraxanthine in DBS, whole blood and plasma. All parameters met the pre-established criteria. While recovery, matrix effects and precision were unaffected by hematocrit (Hct), there was a Hct effect on accuracy, although for the evaluated Hct interval (0.36-0.50) it remained within acceptable limits. The phenotyping methods were successfully applied in healthy volunteers.
  
  
  CONCLUSIONS
  Excellent method performance and highly comparable phenotyping indices in DBS, whole blood and plasma, combined with the benefits of DBS sampling, illustrate the suitability of DBS-based CYP1A2 phenotyping.
authors.affiliation: Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, B-9000 Ghent, Belgium.
authors.forename: Pieter M  M
authors.initials: PM
authors.lastname: De Kesel
authors.forename: Willy E
authors.initials: WE
authors.lastname: Lambert
authors.forename: Christophe P
authors.initials: CP
authors.lastname: Stove
mesh_terms: D002110:Caffeine / Q000097:blood; D002853:Chromatography, Liquid; D019388:Cytochrome P-450 CYP1A2 / Q000097:blood*; D006801:Humans; D010949:Plasma / Q000201:enzymology; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry; D013806:Theophylline / Q000097:blood
chemical_list: D002110:Caffeine; D013806:Theophylline; D019388:Cytochrome P-450 CYP1A2; C021183:1,7-dimethylxanthine