title: Difference in bias approach for commutability assessment: application to frozen pools of human serum measured by 8 direct methods for HDL and LDL cholesterol.
abstract: BACKGROUND
  We used a difference in bias approach to evaluate the commutability of 4 frozen serum pools for 8 direct methods for measurement of HDL and LDL cholesterol (HDLC and LDLC).
  
  
  METHODS
  Freshly collected nonfrozen sera from 138 diseased and 37 nondiseased patients and 4 frozen pools from the CDC Lipid Standardization Program were measured by direct methods and by the beta-quantification reference measurement procedure of the CDC. We used an error components model to estimate the difference in the bias component of error plus its uncertainty for frozen pools vs patient samples between the direct method and the reference procedure. Frozen pools with bias differences less than a critical value determined by either medical requirements for bias or the random error components of the measurement procedures were considered commutable.
  
  
  RESULTS
  On the basis of medical requirement criteria, 1 of the 4 frozen pools was commutable for most of the HDLC methods for both diseased and nondiseased patients, and none was commutable for LDLC methods. On the basis of random error criteria, all of the frozen pools were generally commutable for all of the HDLC methods for both diseased and nondiseased patients, and 1 of the 4 frozen pools was generally commutable for most of the LDLC methods for both diseased and nondiseased patients.
  
  
  CONCLUSIONS
  Commutability was assessed as the closeness of agreement of the difference in bias between a reference material and a set of patient samples. Criteria for commutability could be based on fixed medical requirements for bias or on random error components.
authors.affiliation: Virginia Commonwealth University, Richmond, VA;
authors.forename: William J
authors.initials: WJ
authors.lastname: Korzun
authors.affiliation: Retired, Uppsala, Sweden;
authors.forename: Göran
authors.initials: G
authors.lastname: Nilsson
authors.affiliation: Virginia Commonwealth University, Richmond, VA;
authors.forename: Lorin M
authors.initials: LM
authors.lastname: Bachmann
authors.affiliation: American Association for Clinical Chemistry, Washington, DC;
authors.forename: Gary L
authors.initials: GL
authors.lastname: Myers
authors.affiliation: Jichi Medical University, Tochigi-ken, Japan;
authors.forename: Ikunosuke
authors.initials: I
authors.lastname: Sakurabayashi
authors.affiliation: Otsuka Pharmaceutical, Tokyo, Japan;
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Nakajima
authors.affiliation: Osaka Medical Center for Health Science and Promotion, Osaka, Japan;
authors.forename: Masakazu
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: NIH, Bethesda, MD.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Shamburek
authors.affiliation: NIH, Bethesda, MD.
authors.forename: Alan T
authors.initials: AT
authors.lastname: Remaley
authors.affiliation: Virginia Commonwealth University, Richmond, VA; gmiller@vcu.edu.
authors.forename: W Greg
authors.initials: WG
authors.lastname: Miller
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards*; D008076:Cholesterol, HDL / Q000097:blood*; D008078:Cholesterol, LDL / Q000097:blood*; D006801:Humans; D012015:Reference Standards
chemical_list: D008076:Cholesterol, HDL; D008078:Cholesterol, LDL