title: Clinical validation and implementation of a multiplexed immunosuppressant assay in dried blood spots by LC-MS/MS.
abstract: BACKGROUND
  Therapeutic drug monitoring of immunosuppressive drugs is important in transplant patients. We developed and validated liquid chromatography-mass spectrometry (LC-MS/MS) assay for simultaneous quantitation of tacrolimus (TaC), sirolimus (SrL), and cyclosporin A (CsA) in dried blood spots (DBSs) to offer patients home sample collection, avoiding travel for blood draws.
  
  
  METHODS
  After extraction, samples were analyzed by LC-MS/MS in multiple reaction monitoring mode.
  
  
  RESULTS
  The assay was linear between 1.2-40 ng/ml for TaC and SrL, and 30-1000 ng/ml for CsA. Inter- and intra-assay CVs were ≤14.8% for all 3 drugs. This method correlated well with the existing clinical whole blood assay, with coefficients of determination >0.95 for all 3 drugs. DBS quality control samples were stable for at least 30 days at -20, 4, and 25°C. Stability of patient DBS samples was at least 5 days at temperatures up to 60°C, except for SrL where degradation was observed at 60°C within 24 h. No effect of hematocrit level, blood spot volume or punch location was observed.
  
  
  CONCLUSIONS
  Immunosuppressant levels measured in DBS correlate with whole blood LC-MS/MS assay and may contribute to successful outcome of organ transplant and patient satisfaction.
authors.affiliation: Seattle Children's Hospital, Department of Laboratories, Seattle, WA 98105, United States.
authors.forename: Katerina
authors.initials: K
authors.lastname: Sadilkova
authors.forename: Barbara
authors.initials: B
authors.lastname: Busby
authors.forename: Jane A
authors.initials: JA
authors.lastname: Dickerson
authors.forename: Joe C
authors.initials: JC
authors.lastname: Rutledge
authors.forename: Rhona M
authors.initials: RM
authors.lastname: Jack
mesh_terms: D001800:Blood Specimen Collection / Q000379:methods; D002138:Calibration; D002853:Chromatography, Liquid; D016572:Cyclosporine / Q000097:blood*; D059788:Dried Blood Spot Testing / Q000379:methods* / Q000592:standards; D016903:Drug Monitoring; D006801:Humans; D007166:Immunosuppressive Agents / Q000097:blood*; D016377:Organ Transplantation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020123:Sirolimus / Q000097:blood*; D016559:Tacrolimus / Q000097:blood*; D053719:Tandem Mass Spectrometry
chemical_list: D007166:Immunosuppressive Agents; D016572:Cyclosporine; D020123:Sirolimus; D016559:Tacrolimus