InterlaboratoryTestingof the Transferabilityof a CandidateReference

in 1975 the Centers for Disease Control, in cooperation with the American Association for Clinical Chemistry Cholesterol Reference Method Study Group, began an investigation to develop a reference method for total cholesterol. Five potential reference methods were compared with the definitive method developed by the National Bureau of Standards before the chemical method of Abell et al. (J Biol Chem 1952;195:357-66) was selected as the recommended reference method. Because acceptance of a proposed reference method depends so greatly on the method’s capability for transfer to other laboratories by written specifications and instructions, a transferability testing study was designed and conducted with 14 laboratorIes. The study consisted of preliminary testing of readiness of equipment, reagents, and personnel followed by transferability testing with eight runs on 10 serum pools. Laboratories that did not meet readiness specifications had higher CVs in the transferability testing. The study demonstrated that the proposed method permits laboratories to attain a CV of <1.5% for one laboratory and of <3.0% among laboratories. The mean percent bias value was <1.0% for six of the 14 laboratories, <1.5% for 12, and <3.0% for all 14 laboratories.