title: Determination of biological variation of α-fetoprotein and choriogonadotropin (β chain) in disease-free patients with testicular cancer.
abstract: BACKGROUND
  Knowledge of biological variation (BV) is important for determining analytical goals and for establishing the magnitude of change between two consecutive measurements which indicate change in a patients' health status. The aim of this work is to determine the BV for total choriogonadotropin (β chain) (β-hCG) and α-fetoprotein (AFP) in patients diagnosed with testicular cancer but with no evidence of recurrence of disease.
  
  
  METHODS
  We estimated BV from a mean of five consecutive measurements in 28 patients diagnosed with testicular cancer, 3 months after tumor resection or 4 months after complete treatment with chemotherapy. The mean sampling interval was 3 months.
  
  
  RESULTS
  The mean concentrations of α-fetoprotein and choriogonadotropin (β chain) were 3.9 μg/L and 0.79 IU/L, respectively. Between-run analytical variation was 7.1% at 4.1 μg/L for α-fetoprotein, and 19% at 0.65 IU/L for choriogonadotropin (β chain). BV obtained for α-fetoprotein and choriogonadotropin (β chain) was 12.4% and 16.7%, respectively, and the reference change value (RCV) for one-tail showed 38.2% and 60.7% for α-fetoprotein and choriogonadotropin (β chain), respectively.
  
  
  CONCLUSIONS
  The estimation of BV allows us to calculate analytical goals and RCVs, necessary tools for the correct interpretation of serial measurements in the follow-up of patients.
authors.affiliation: Service of Clinical Chemistry, Hospital Sant Joan de Deu de Manresa, Althaia Xarxa Assistencial de Manresa, Manresa, Catalonia, Spain. jtrape@althaia.cat
authors.forename: Jaume
authors.initials: J
authors.lastname: Trapé
authors.forename: Josefina
authors.initials: J
authors.lastname: Franquesa
authors.forename: Maria
authors.initials: M
authors.lastname: Sala
authors.forename: Montserrat
authors.initials: M
authors.lastname: Domenech
authors.forename: Jesus
authors.initials: J
authors.lastname: Montesinos
authors.forename: Sílvia
authors.initials: S
authors.lastname: Catot
authors.forename: Josep
authors.initials: J
authors.lastname: Buxó
authors.forename: Esther
authors.initials: E
authors.lastname: Casado
authors.forename: Cristina
authors.initials: C
authors.lastname: Fígols
authors.forename: Sílvia
authors.initials: S
authors.lastname: Harillo
authors.forename: Judit
authors.initials: J
authors.lastname: Galobart
authors.forename: Meritxell
authors.initials: M
authors.lastname: Bella
mesh_terms: D006063:Chorionic Gonadotropin / Q000032:analysis*; D006801:Humans; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D013736:Testicular Neoplasms / Q000175:diagnosis* / Q000628:therapy; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins