ABSTRACT
Objective To improve EP9-A2 for Bias estimation among multiple quantitative detection systems within full range of AMR.Methods 40 patients specimens were determined twice for serum total cholesterol by four detection systems(A,B,C and D).With system A served as comparative method,Bias between A and the other three was evaluated according to CLSI EP9-A2 separately.Furthermore,DD(distance from deviation to tolerable error)and its average confidence intervals between every two sys-tem were calculated and compared with zero.The confidence interval of greater than zero was served as criteria for accepting bias between every two system.Results Bias between A and the other three meet the analytical quality specification according to EP9-A2,although that of D system was positive,and those of B and C system were negative.DD between every two system obeyed nor-mality distribution.All biases between every two system wes acceptable except that between B and D,causing of their interval con-taining zero.After correcting of results from system D,Biases between every two system were all acceptable.Plots of confidence in-terval could provide a full range bias assessment within AMR.Conclusion Comparability and Bias estimation in full range of AMR for results between every two system among 3 or more systems could be evaluated by confidence intervals.
ABSTRACT
ObjectiveTo establish a enzyme-linked immunosorbent assay (ELISA) method for detecting the β-amyloid peptide 42 ( Aβ42 ) and explore its clinical meaning for diagnosis and treatment in the early stages of the alzheimer disease ( AD).Methods Using the Aβ42 single chain variable fragment constructed by phage antibody library display system as coat antibody,associated with the Aβ42 polyclonal antibody acquired by Aβ42 immunized rabbit and HRP labeled goat anti rabbit IgG to establish ELISA method for detecting the Aβ42 in peripheral blood.The method was used it to test the Aβ42 in 120 vascular dementia VD) or cerebral vessel infarction patients and 120 AD patients and 120 controls.The methodology performance were evaluated.ResultsThe inter and intra coefficient of variable (CV) of this self-established ELISA method was 3.6％ and 3.5％,6.8％ and 7.1％ respectively.The recovery rate was 97.2％ -103.1％.The linear range was 0.050 - 2 μg,/L.Its reactivity decreased ＜ 12％ when it was put in both 37 ℃ for 6 days and 4 ℃ for 6 months.Compared with the Belgium INNOTEST reagent by testing 90 samples simultaneously,the results of self-established method was (0.207 ± 0.039 ) μg/L,the results of INNOTEST was (0.206± 0.038 ) μg/L; the regression equation was Y =1.011X - 0.003,R2 =0.979,P ＜0.01.The Aβ42 in blood of AD group was (0.247 ± 0.032 ) μg/L,VD or cerebral vessel infarction group was (0.173 ±0.028) μg/L,control group was (0.172 ±0.032) μg/L.The Aβ42 in AD group was higher than that in the VD or cerebral vessel infarction group and control group (q =18.867,18.907respectively,P ＜ 0.01 ).The cut off value was 0.212 μg/L decided by the receiver operating characteristic (ROC) curve.The reference interval was 0 -0.212 μg/L.The sensitivity of this ELISA method was 86.7％(104/120) and specificity was 90.8％ (218/240).ConclusionsThe ELISA method for detecting Aβ42 in peripheral blood established by the study is sensitive and specific and has good precision and stability.It could provide a new effective criterion and support for the early diagnosis and treatment of the AD patients.