title: Abbott ARCHITECT iPhenytoin assay versus similar assays for measuring free phenytoin concentrations.
abstract: OBJECTIVE
  To measure free phenytoin (FP) concentrations in filtered specimens using the Abbott ARCHITECT iPhenytoin assay and to compare results from this method with results from the Abbott TDx/FLx assays.
  
  
  METHODS
  We verified accuracy, analytic measurement range, and precision for FP measurements. For correlation and therapeutic interval studies, we used filtered calibrators, controls, proficiency-testing materials, and surplus clinical samples. After implementation, we determined proficiency testing results.
  
  
  RESULTS
  The analytic measurement range was 2.0 to 25.0 micromol/L. Quality control materials (6.1, 12.6, and 20.1 micromol/L) provided mean (SD) recoveries of 96.1 (5.0%), 99.2 (5.0%), and 99.3 (5.7%), respectively, and coefficients of variation of 5.2%, 5.0%, and 5.8%, respectively. Clinical specimens produced mean (SD) FP recovery levels of 103.7 (10.6%) (bias, 0.1 [0.3] micromol/L). Altering the FP therapeutic range (4.0-8.0 micromol/L) was unnecessary. Proficiency testing yielded consistently acceptable results.
  
  
  CONCLUSIONS
  Our accuracy, precision, and correlation results were similar for the TDx/FLx and ARCHITECT assays, which demonstrates that the ARCHITECT iPhenytoin assay is acceptable for clinical FP measurements.
authors.forename: Danyel Hermes
authors.initials: DH
authors.lastname: Tacker
authors.forename: Randy
authors.initials: R
authors.lastname: Robinson
authors.forename: Peter L
authors.initials: PL
authors.lastname: Perrotta
mesh_terms: D000927:Anticonvulsants / Q000097:blood*; D057205:Automation, Laboratory; D005454:Fluorescence Polarization; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D059021:Laboratory Proficiency Testing / Q000592:standards*; D010672:Phenytoin / Q000097:blood*; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014462:Ultrafiltration
chemical_list: D000927:Anticonvulsants; D010672:Phenytoin