血清尿素测定基质效应研究

Evaluation of matrix effects in serum urea measurements

目的评价2007年全国室间质量评价（EQA）临床化学项目材料和13种市售制备物血清尿素测定在7种脲紫外速率法测定系统上的基质效应，并考察这些测定系统的校准偏差。方法按美国临床和实验室标准协会（CLSI）EP 14-A2试验方案，同位素稀释气相色谱质谱法作比对方法，7种尿素酶常规方法为待评方法，用比对方法和待评方法同时测定25份新鲜冰冻人血清和EQA材料及市售制备物。考察常规方法和比对方法测定EQA材料（或市售制备物）结果间的数量关系与它们测定新鲜冰冻人血清样品数量关系的一致程度，评价样品的基质效应。考察新鲜冰冻人血清样品常规方法和比对方法结果的差异，评价测定系统的校准偏差。结果8种EQA材料和3种市售制备物对参加评价的所有测定系统无基质效应，1种市售制备物对所有系统都表现基质效应，其他样品视系统的不同而表现出不同的情况。7种测定系统中的6种都存在不同程度的校准偏差：同直线Y=X相比，系统A的斜率、截距偏差均小于5％，不存在明显校准偏差。系统B、C、D、F、G的斜率偏差小于5％，截距偏差大于5％，存在一定的校准偏差。系统E的斜率和截距偏差均大于5％，表现为存在校准偏差。结论样品的基质效应和测定系统的校准偏差影响血清尿素测定的准确性和可比性。应充分重视基质效应和校准偏差对临床检验量值溯源的影响。

Objective To evaluate the matrix effects in serum urea measurements of external quality assessment （EQA） materials and commercial reference materials （calibrators or controls ） on enzymatic methods and to verify the trueness of the enzymatic methods. Methods The Clinical and Laboratory Stadards Institute（CLSI） EP 14-A2 protocol was used for the evaluation of matrix effect. An isotope dilution gas chromatography mass spectrometry method was used as the comparative method. Twenty five fresh patient serum samples, 15 EQA materials and 13 calibrators or controls were analyzed with 7 enzymatic methods （evaluated methods） and the comparative method and results were processed according to the protocol. The trueness of the evaluated methods were also assessed by comparing the fresh sample results obtained with the evaluated and comparative methods. Results Eight of 15 EQA materials and 3 of 13 calibrators or controls showed no matrix effects on all the 7 routine methods. One processed sample showed matrix effect on all the routine methods. Method dependent matrix effects of other materials were observed on other materials. Calibration biases were also observed on some enzymatic methods. Conclusions Matrix effects and calibration bias have been observed in serum urea measurements. Continued efforts are needed for improving the accuracy and the comparability of serum urea measurements.