title: Comparison of digoxin concentration in plastic serum tubes with clot activator and heparinized plasma tubes.
abstract: BACKGROUND
  Sample type recommended by the manufacturer for the digoxin Abbott assay is either serum collected in glass tubes or plasma (sodium heparin, lithium heparin, citrate, EDTA or oxalate as anticoagulant) collected in plastic tubes. In our hospital samples are collected in plastic tubes. Our hypothesis was that the serum sample collected in plastic serum tube can be used interchangeably with plasma sample for measurement of digoxin concentration. Our aim was verification of plastic serum tubes for determination of digoxin concentration.
  
  
  METHODS
  Concentration of digoxin was determined simultaneously in 26 venous blood plasma (plastic Vacuette, LH Lithium heparin) and serum (plastic Vacuette, Z Serum Clot activator; both Greiner Bio-One GmbH, Kremsmünster, Austria) samples, on Abbott AxSYM analyzer using the original Abbott Digoxin III assay (Abbott, Wiesbaden, Germany). Tube comparability was assessed using the Passing Bablok regression and Bland-Altman plot.
  
  
  RESULTS
  Serum and plasma digoxin concentrations are comparable. Passing Bablok intercept (0.08 [95% CI = -0.10 to 0.20]) and slope (0.99 [95% CI = 0.92 to 1.11]) showed there is no constant or proportional error.
  
  
  CONCLUSIONS
  Blood samples drawn in plastic serum tubes and plastic plasma tubes can be interchangeably used for determination of digoxin concentration.
authors.affiliation: University Department of Chemistry, Medical School University Hospital Sestre Milosrdnice, Zagreb, Croatia.
authors.forename: Lora
authors.initials: L
authors.lastname: Dukić
authors.affiliation: University Department of Chemistry, Medical School University Hospital Sestre Milosrdnice, Zagreb, Croatia.
authors.forename: Ana-Maria
authors.initials: AM
authors.lastname: Simundić
authors.affiliation: University Department of Chemistry, Medical School University Hospital Sestre Milosrdnice, Zagreb, Croatia.
authors.forename: Davorin
authors.initials: D
authors.lastname: Malogorski
mesh_terms: D000925:Anticoagulants / Q000737:chemistry*; D001774:Blood Chemical Analysis / Q000379:methods; D001800:Blood Specimen Collection / Q000295:instrumentation* / Q000379:methods*; D004077:Digoxin / Q000032:analysis*; D006493:Heparin / Q000737:chemistry*; D006801:Humans; D010969:Plastics
chemical_list: D000925:Anticoagulants; D010969:Plastics; D004077:Digoxin; D006493:Heparin
keywords: digoxin; evaluation; plasma; serum; specimen collection; therapeutic drug monitoring