CANDIDATE REFERENCE METHODS FOR DETERMINING TARGET VALUES FOR CHOLESTEROL, CREATININE, URIC-ACID, AND GLUCOSE IN EXTERNAL QUALITY ASSESSMENT AND INTERNAL ACCURACY CONTROL .2. METHOD TRANSFER

We describe the testing of transferability of candidate Reference Meth ods developed by INSTAND for cholesterol, creatinine, uric acid, and g lucose. The methods are based on isotope dilution-gas chromatography-m ass spectrometry. The study consisted of two parts: setup of the metho ds and self-evaluation for readiness in the collaborating laboratory, followed by independent measurements in parallel with INSTAND. Criteri a used for judging the transferability and general reliability of the candidate Reference Methods were: the accuracy and precision of the co llaborating laboratory and the agreement between the two laboratories. The accuracy was judged from the results on the Standard Reference Ma terial 909 from the National Institute of Standards and Technology. Fo r all analytes except glucose the bias from the certified value was <0 .7%. The mean intralaboratory imprecision ranged from 0.66% to 1.24%. The agreement between the results was tested by an advanced linear-reg ression analysis and Student's t-test. In general, the results demonst rate that the candidate Reference Methods developed by INSTAND can be successfully transferred without loss of their inherent precision and accuracy.