title: Evaluation of commutability of several materials for harmonization alkaline phosphatase catalytic concentration measurements.
abstract: BACKGROUND
  The International Standard ISO 18153 establish that one of the requirements to assure the metrological traceability of values for catalytic concentration of enzymes is the commutability of calibrator and control materials used in the reference measurement systems. This approach was applied to verify the commutability of several commercial stabilized materials using the recently published alkaline phosphatase IFCC primary reference procedure and two routine procedures.
  
  
  METHODS
  ALP catalytic activity was measured in 50 serum samples and 16 commercial materials, including control materials from EQAS programs, using primary reference measurement procedure and two routine measurement procedures with AMP and DEA as buffers. Calibration materials with a value assigned by reference procedure which were proved to be commutable were used to recalculate the serum values obtained by routine procedures.
  
  
  RESULTS
  All commercial materials showed a similar behaviour to the patient specimens when AMP vs IFCC procedures were compared. For DEA vs IFCC comparison only one calibration material and two quality control materials were commutable. Recalculation of serum results with a commutable common calibrator improves the agreement between methods changing the ratio AMP vs IFCC from 1.44 to 1.04 and DEA vs IFCC from 3.02 to 1.05.
  
  
  CONCLUSIONS
  The use of a common commutable calibration material allows harmonizing ALP measurements and made traceable patient results to reference procedure.
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Unitat de Bioquímica de Medicina, Universitat Autònoma de Barcelona, Bellaterra, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Rami
authors.forename: Montserrat
authors.initials: M
authors.lastname: Roura
authors.forename: Francesca
authors.initials: F
authors.lastname: Canalias
mesh_terms: D000469:Alkaline Phosphatase / Q000032:analysis* / Q000097:blood; D002021:Buffers; D004796:Clinical Enzyme Tests / Q000592:standards*; D006801:Humans; D011786:Quality Control; D012015:Reference Standards
chemical_list: D002021:Buffers; D000469:Alkaline Phosphatase