Calibration mode and harmonization of CK and LDH results

Abstract

Objective Using the frozen human-pooled serum samples assigned by the enzymology reference procedure laboratory network as the calibrator, to find the way for harmonizing results among different measurement systems of enzymology, and providing a reference method for clinical laboratory to determine the appropriate calibration mode. Methods The study is about quantity traceability.Using the frozen human-pooled serum sample assigned by the enzymology reference laboratory network consisted of six domestic reference laboratories，namely Beijing Chaoyang Hospital affiliate of Capital University of Medical Sciences, Beijing Aerospace general Hospital, Beijing Shijitan Hospital affiliate of Capital University of Medical Sciences, Peking Union Medical College Hospital, Beijing Leadman Biochemistry Co.，ltd, Sichuan Maker Biotechnology Co., ltd, using the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference measurement procedures of creatine kinase (CK) and lactate dehydrogenase (LDH) as the same calibrator, to calibrate eight measurement systems with single point calibration mode of routine laboratories In February 2012 in Beijing.The value-assigned human sample、manufacturers′ calibrators、control materials and the patient samples were detected after each measurement system was calibrated by daily calibration.The patient samples were collected by Beijing Center for Clinical Laboratories between September and November 2011 from Chinese academy of medical sciences Fuwai hospital cardiovascular disease.Then, each results were recalculated with the another procedure which was fixed by average calibration factor of ten days (hereinafter referred to as fixed K).Then, we had compared statistical results for the two procedures.The statistical indicators of mean, standard deviation, coefficient of variation of the patient samples were calculated before and after calibration and the biases of the original system calibrators were also done. Results After calibration, the biases of eight original detection system calibrators were different, two out of eight were bigger than 5% for both CK and LDH.The coefficients of variation (CVs) of the two patient samples of CK dropped by 3.78% and 3.78% to 4.44% and 3.78% respectively; LDH dropped by 4.11% and 4.11% to 4.08% and 4.11%.The statistical results of two procedures showed that under the circumstance of the CVs of calibration factor for CK and LDH were not bigger than 1.00% and 2.50%, the intra-detection system CVs of all the sample results were less than 1.50% and 3.00%. It was no significant difference between the two procedures in CVs of the original system calibration product, control materials and the patient samples.While on the condition that the CVs of calibration factor for CK and LDH were larger than 1.00% and 2.50%, the intra-detection system CVs increased and the CVs of fixed K of all samples were larger than those of daily calibration. Conclusions Using the frozen human-pooled serum samples assigned by the enzymology reference procedure laboratory network as the calibrator, to calibrator the different measurement system with calibration mode of single point, can realize the consistency of the testing results of CK and LDH, and making the results traceable to the reference measurement procedure. Laboratory should base on the stability of the detection system to determine the appropriate calibration mode.（Chin J Lab Med，2014,37：50-55） Key words: Creatine kinase; Lactate dehydrogenases; Calibration; Reproducibility of results