Serum triglyceride measurements: the commutability of reference materials and the accuracy of results

Background We aimed to evaluate the commutability of external quality assessment (EQA) materials, aqueous solutions, and commercial reference materials (calibrators and controls), and the accuracy of routine systems for serum triglyceride measurements. Methods According to the clinical and laboratory standards institute (CLSI) EP14-A3 protocol, we analyzed 43 fresh patient specimens and 32 processed materials including lyophilized samples, human serum pools, liquid reagents, swine sera and aqueous solutions by 14 routine methods (evaluated methods) and an isotope dilution liquid chromatography tandem mass spectrometry method (ID-LC/MS/MS) (comparative method). The accuracy of the routine method was evaluated by analyzing the absolute bias, relative bias, and the bias at three medical decision levels based on CLSI EP9-A3. Results Frozen serum samples and swine sera were commutable for all of the assays. The EQA/PT materials, commercial calibrators and control materials showed matrix effects differently on routine methods. The aqueous glycerol solutions were generally noncommutable for routine method. All except one routine analytical systems met the National Cholesterol Education Program (NCEP) recommended analytical performance guideline analytical quality criteria for total error. Conclusions Matrix effects and calibration biases existed in measurements of serum triglyceride. Continued efforts are needed to improve the accuracy and comparability of routine measurements.