title: Biological variations of ADAMTS13 and von Willebrand factor in human adults.
abstract: BACKGROUND
  The ultra-large von Willebrand factor (vWF) multimers are very active and must be degraded by ADAMTS13 for optimal activity. A severe functional deficiency of ADAMTS13 has been associated with thrombotic thrombocytopenic purpura. The correct interpretation of patient vWF and ADAMTS13 plasma levels requires an understanding of the biological variation associated with these analytes. In the present paper, we aimed to determine the biological variation of ADAMTS13 and vWF in human adults.
  
  
  METHODS
  Blood samples were collected weekly from 19 healthy subjects for 5 consecutive weeks. vWF activity and antigenicity were determined using aggregometric and immunoturbidimetric methods. ADAMTS13 antigenicity and activity were determined by ELISA.
  
  
  RESULTS
  The within-subject biological variations for vWF activity and antigenicity were 8.06% and 14.37%, respectively, while the between-subject biological variations were 18.5% and 22.59%, respectively. The index of individuality for vWF activity was 0.44, while vWF antigenicity was 0.64. Similarly, ADAMTS13 activity and antigenicity within-subject biological variations were 12.73% and 9.75%, respectively, while between-subject biological variations were 9.63% and 6.28%, respectively. The ADAMTS13 indexes of individuality were 1.32 and 1.55, respectively.
  
  
  CONCLUSIONS
  We report high biological variation and individuality in vWF antigenicity and activity levels. However, ADAMTS13 antigenicity and activity displayed high biological variation, but low individuality. Thus, population-based reference intervals may be useful for monitoring ADAMTS13 antigenicity and activity, but not for vWF, which displays high individuality. These findings should be considered when determining the reference interval and other clinical variables associated with ADAMTS13 and vWF levels.
authors.affiliation: Acibadem University, School of Medicine, Department of Medical Biochemistry, Istanbul, Turkey.
authors.forename: Meltem
authors.initials: M
authors.lastname: Kilercik
authors.affiliation: Acibadem University, School of Medicine, Department of Medical Biochemistry, Istanbul, Turkey.
authors.forename: Abdurrahman
authors.initials: A
authors.lastname: Coskun
authors.affiliation: Acibadem University, School of Medicine, Department of Medical Biochemistry, Istanbul, Turkey.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Serteser
authors.affiliation: Marmara University, Arts and Science Faculty, Department of Statistics, Istanbul, Turkey.
authors.forename: Deniz
authors.initials: D
authors.lastname: Inan
authors.affiliation: Acibadem University, School of Medicine, Department of Medical Biochemistry, Istanbul, Turkey.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Unsal
mesh_terms: D051722:ADAM Proteins / Q000276:immunology* / Q000378:metabolism*; D000071120:ADAMTS13 Protein; D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D011786:Quality Control; D012016:Reference Values; D055815:Young Adult; D014841:von Willebrand Factor / Q000276:immunology* / Q000378:metabolism*
chemical_list: D014841:von Willebrand Factor; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human
keywords: ADAMTS13; individuality; thrombotic thrombocytopenic purpura; variation analysis; von Willebrand factor