同位素稀释质谱法测定血清肌酐浓度的不确定度评定

目的探讨同位素稀释质谱法(ID-MS)测量血清肌酐浓度的不确定度评定方法。方法应用ID-MS建立测定血清肌酐浓度的参考测量程序,严格按照《测量不确定度表示指南》(简称GUM)评定不确定度,即严格根据测量模型对各不确定度分量进行详细分析和定量,加减项用绝对值、乘除项用相对值合成各标准不确定度分量;同时,用传统评定方法和蒙特卡洛方法(MCM)分别对血清肌酐浓度测量结果进行不确定度评定。结果对特定血清进行赋值,其肌酐浓度为347.4μmol/L。按照ID-MS测量模型,并严格应用GUM原理进行不确定度评定,其合成标准不确定度的相对值为0.89%,而传统方法评定结果为0.93%,较GUM法高4.8%;采用MCM评定各不确定度分量,其合成标准不确定度的相对值为0.64%,较严格GUM法低27.9%,其测量结果的95%可信区间为343.1~351.8μmol/L。结论与GUM法评定结果比较,传统评定方法结果偏高,而MCM偏低,3种评定方法存在差异。建议采用GUM法,根据测量模型对各不确定度分量进行定量和合成。有条件的话,可用MCM评定不确定度。

Isotope dilution mass spectrometry applied in measurement uncertainty of serum creatinine concentration

Objective To investigate the evaluation method for measurement uncertainties of serum creatinine concentration by isotope dilution mass spectrometry(ID-MS).Methods We established a reference measurement procedure for the serum creatinine concentration by ID-MS.The uncertainty was evaluated according to the strict Guide to the Expression of Measurement Uncertainty(GUM)method.The strict GUM method meant that each uncertain component was analyzed and quantified in detail according to the measurement model.The calculation was based on the principle that relative values should be used in multiplication and division,and absolute values should be used in addition and subtraction.Meanwhile,traditional evaluation method and the Monte Carlo method(MCM)were used to evaluate the uncertainties of serum creatinine concentration.Results The measured specific serum creatinine concentration was 347.4μmol/L.The combined standard uncertainty was 0.89%according to ID-MS measurement model and strict GUM principle.The uncertainty evaluated by the traditional method was 0.93%,which was 4.8%higher than that evaluated by the GUM method.The combined standard uncertainty was 0.64%by MCM,which was 27.9%lower than that evaluated by the strict GUM method.The 95%confidence interval of the measurement result by MCM was 343.1-351.8μmol/L.Conclusions The result of uncertainty evaluated by the traditional method is higher than that of the strict GUM method,while the result of the MCM is lower than that of the strict GUM method.It is suggested that each uncertainty component should be strictly quantified and combined according to the GUM method.If possible,the MCM could be used to evaluate the uncertainty.