评估液相免疫胶体金试剂盒应用于全自动生化分析仪检测半胱氨酸蛋白酶抑制剂C(Cys C)的方法学性能及其与肾小球滤过功能的相关性。

分别采用液相免疫胶体金试剂盒与颗粒增强散射免疫比浊法(PENIA)测定Cys C,评价的方法学指标为精密度、线性范围、抗干扰性、相关及偏倚。同时采用锝标记二乙烯三胺五乙酸(^99mTc-DTPA)肾动态显像测定97例慢性肾病患者肾小球滤过率(GFR),并与血浆Cys C浓度进行相关性评估。采用受试者工作特征(ROC)曲线评价血浆Cys C对肾小球滤过功能减退的诊断价值。

Cys C在低、中、高浓度水平总变异分别为5.27%、5.23%和2.81%。在0.54~8.65 mg/L范围内显示良好的线性。血红蛋白<10 g/L、胆红素<300 mg/L时对测定结果的干扰<10%;三酰甘油(TG)≥20 mmol/L时对低浓度样本的影响度超过10%,对高浓度样本无明显干扰。液相免疫胶体金试剂盒与PENIA相关性良好( r=0.99, P<0.01),2种方法间的差异无统计学意义( P>0.10)。液相免疫胶体金试剂盒测定结果较PENIA结果偏高,平均偏倚为0.27 mg/L。血浆Cys C浓度与GFR显著相关( r=-0.829, P<0.001);血浆Cys C诊断肾功能减退的ROC曲线下面积为0.826(95%可信区间:0.716~0.936)。以正确诊断指数最大处的观察值1.11 mg/L作为判断Cys C升高的依据,当GFR≥80 mL/(min·1.73 m²)时,24.3%的患者血浆Cys C升高;GFR为50~80 mL/(min·1.73 m²),70%的患者血浆Cys C升高;GFR≤50 mL/(min·1.73 m²),所有患者血浆Cys C升高。

液相免疫胶体金试剂盒应用于全自动生化分析仪检测Cys C的精密度、抗干扰性能、线性范围符合临床要求,而且与PENIA有良好的相关性,但2种方法的测定结果存在一定的偏倚。血浆Cys C是评估肾小球滤过功能的理想指标。

To evaluate the methodology performance of determining cystatin C (Cys C) by liquid immune colloidal gold reagent on the automatic biochemical analyzer and the correlation between Cys C results and glomerular filtration function.

Cys C concentration was determinated by liquid immune colloidal gold reagent and particle-enhanced nephelometric immunoassay (PENIA) respectively. The precision, linearity and interference of Cys C liquid immune colloidal gold reagent,its correlation and the bias with PENIA were evaluated. The correlation analysis was performed between plasma Cys C concentrations and glomerular filtration rate (GFR) determined by^99mtechnetium-labeled diethylenetriamine penta-acetic acid (^99mTc-DTPA) renal dynamic imaging of 97 patients with chronic renal disease. The receiver operating characteristic (ROC) curve was used to evaluate the value of plasma Cys C in the diagnosis of renal function reduction.

The total coefficients of variation ( CV) of samples with low, medium and high concentrations of Cys C were 5.27%, 5.23% and 2.81% respectively. This reagent showed good linearity ranged from 0.54 to 8.65 mg/L. Hemoglobin (<10 g/L) and bilirubin (<300 mg/L) in the samples had no significant interference (<10%) in the assay. The interference was more than 10% for the samples of low Cys C concentration when triglycerides (TG) ≥20 mmol/L, while the interference was not significant to the samples of high Cys C concentration. The results by liquid immune colloidal gold reagent correlated well with those by PENIA ( r=0.99, P<0.01). There was no significant bias between these two methods( P>0.10). However, the values were slightly higher than those from PENIA with the mean bias of 0.27 mg/L. Plasma Cys C concentrations showed significant correlation with GFR ( r=-0.829, P<0.001). The area under the ROC curve (AUC) was 0.826 [95% confidence interval ( CI): 0.716-0.936] for plasma Cys C in the diagnosis of renal function reduction. When the optimal cut-off value (1.11 mg/L) was used to discriminate the elevated values from the normal values, 24.3% of the patients with GFR≥80 mL/(min·1.73 m²) showed increased concentration of Cys C. Plasma Cys C concentrations increased in 70% of the patients with GFR between 50 and 80 mL/(min·1.73 m²) and all the patients with GFR≤50 mL/(min·1.73 m²).

The precision,linearity and interference of Cys C liquid immune colloidal gold technique on the automatic biochemical analyzer are suitable for the requirements of clinical application. The liquid immune colloidal gold technique correlates well with PENIA, but there exists bias between these two methods. Plasma Cys C is an ideal indicator in the evaluation of glomerular filtration function.