Determined The Best Cut-off Values Of HCV Antibody Tested By ELISA And Compared With The Four Reagents

Object: To investigate determined the best cut-off value under the condition of positivedetection of hepatitis C virus(HCV) antibody by ELISA, and compared the domestic commonly used four reagents of sensitivity and specificity.Methods:1. The high and low concentration of quality products were parallelly tested 20 times, and evaluating the CV within the group of precision. Then high and low concentration of quality products were tested two holes every day and consecutively detected of 20 days,last Calculating the CV between the group of precision.2. 130 serum samples detected positive of HCV antibody by ELISA and 45 negative specimens but close to the critical value(OD = 0.15-2.0) from patients or people who did physical examination in our hospital were chosen and recombinant immune blot assay(RIBA) was used to confirm them positive or negative.3. Under the condition of the cut-off value given by the current reagent instructions, the testresults of ELISA method and RIBA method Kappa value.Then estimating the sensitivity and specificity about HCV antibody detected by ELISA.4. Drawing the ROC curve through SPSS17.0 and selecting the highest point of tangency for the critical point,then determining the best cut-off value. Under the condition of the new cut-off value,Assessing ELISA method and RIBA method Kappa value with the test results. Then estimating the sensitivity and specificity about HCV antibody detected by ELISA.5. Selecting laboratory commonly used four reagents disorderly plaited for A, B, C, D. Before the experiment, evaluating the CV within the group of precision and the CV between the group of precision. If they can meet the requirements of the laboratory, four reagents would detected the serum samples which confirmed by the RIBA method.Then Calculating the sensitivity and specificityof A, B, C, D reagent.Results:1.The CV within the group of precision of high and low concentration of quality products were 9.58% and 10.08%, and the CV between the group of precision were 12.08% and 13.78%.2. After confirmed by the RIBA method, ELISA method and RIBA method Kappa value consistent with the test results Kappa is 0.676,and the sensitivity is 98.17% and specificityis 65.15% of ELISA method. Then, significance(P<0.05)between the two test methods。3. Through the ROC curve, determining the best cut-off value is 0.252 of the CO, And, The Kappa of two methods is 0.829 and the sensitivity is 98.17% and specificityis 65.15% of ELISA method.However, no significance(P>0.05)between the two methods。4. Through the ROC curve, determining the best cut-off value is 2.44 of the S/CO, And, the sensitivity is 93.6% and specificityis 96.1% of the ELISA.5. Before four reagents testing, The CV within the group of precision of quality products was 9.82% and the CV between the group of precision was 13.17%.6. The sensitivity is 99.08% and specificity is 72.73% of A reagent and the sensitivity is 99.08% and specificity is75.76% of B reagent. And,the C reagent’s sensitivity is 98.08% and specificity is 72.73%. However,the D reagent’s sensitivity is 99.08% and specificity is 74.24%. And,no significance(P>0.05)between the four regeats.Conclusions:1.The cut-off value given by the current reagent instructions may be different from the virtual cut-off value of the laboratory.2.By means of the ROC curve analysis in the clinical laboratory, the best cut-off value can be found to help provide reliable results for clinical.3. There usually exists higher sensitivity about homemade reagent, And there exists different sensitivity and specificity between different reagents.4. we suggest different laboratories should establish suitable Cut-off value according to the reagent, in order to reduce missed diagnosis and misdiagnosis of specimens,...