Objective To establish the enzyme-linked immunosorbent assay (ELISA) methods for the quantitative determination of IgG antibodies against diphtheria (DT) and tetanus (TT).MethodsPurified diphtheria toxiod and tetanus toxoid were respectively used as the coating antigens,the human-derived serum antibody standard substance of DT and TT served as the standard substance.The dose-response curves of the tested samples and standard substance were fitted.Then the two quantitative ELISA methods for determining the antibody to DT (Anti-DT) and antibody to TT (Anti-TT) were established with the parallel lines method.Then the methodological verification and application study were conducted.Results The validation results of the two quantitative ELISA measurement methods were in accordance with the regulations.The quantity limit of ELISA method for quantitative detection of Anti-DT demonstrated to be 0.084 mIU/mL,its average recovery rate was 97.6%.The intra-assay coefficient of variation(CV) and inter-assay CV of this Anti-DT assay were ≤ 3.40% and ≤5.05%,respectively.The quantity limit of ELISA method for quantitative detection of Anti-TT demonstrated to be 0.175 mIU/mL,its average recovery rate was 97.5%.The intra-assay CV and inter-assay CV of this Anti-TT assay were ≤ 2.42% and ≤5.58%,respectively.These two methods were applied for the immunogenicity evaluation after infantile basic immunization by diphtheria and tetanus vaccines.Conclusion The two established quantitative ELISA methods demonstrate high accuracy and good reproducibility,which are suitable for the ordinary laboratory to carry out the work and can be used in the serological effect evaluation after diphtheria and tetanus vaccine immunization and epidemiological study of diphtheria and tetanus disease.

Objective:To study the correlation between serum bilirubin and cystatin C in patients with type 2 diabetes mellitus.Methods:A retrospective cohort study was conducted on 750 patients who were in the Affiliated Hospital of Jining Medical University from June 2017 to May 2018. The clinical data were collected, and the correlation between serum total bilirubin, direct bilirubin, indirect bilirubin and cystatin C was analyzed.Results:According to the results of single factor analysis, after adjusting the related confounding factors, the smooth curve fitting showed that there was a U-shaped relationship between the total bilirubin, indirect bilirubin and cystatin C. When the total bilirubin was <15.9 μmol/L, for every increase of 1 μmol/L in total bilirubin, cystatin C decreased 0.008 mg/L ( β = - 0.008, 95% CI - 0.014 to - 0.002, P<0.01); when indirect bilirubin was <11.5 μmol/L, for every increase of 1 μmol/L in indirect bilirubin, cystatin C decreased 0.011 mg/L ( β = - 0.011, 95% CI - 0.018 to - 0.003, P<0.01). When cystatin C was grouped according to the normal range (cystatin C<1.25 mg/L), after adjusting the related confounding factors, the smooth curve fitting showed that there was a U-shaped relationship between the total bilirubin and indirect bilirubin with cystatin C; when total bilirubin was <15.5 mol/L, for every increase of 1 μmol/L in total bilirubin, the risk of cystatin C exceeding the normal value was reduced by 17% ( OR = 0.83, 95% CI 0.71 to 0.96, P<0.01); when total bilirubin was ≥15.5 μmol/L, for every increase of 1 μmol/L in total bilirubin, the risk of cystatin C exceeding the normal value was increased by 12% ( OR = 1.12, 95% CI 1.01 to 1.25, P<0.05); when indirect bilirubin was <11.8 μmol/L, every increase of 1 μmol/L in indirect bilirubin, the risk of cystatin C exceeding the normal value was reduced by 20% ( OR = 0.80, 95% CI 0.67 to 0.95, P<0.01). However there was no significant correlation between direct bilirubin and cystatin C. Conclusions:There is a U-shaped relationship between total bilirubin, indirect bilirubin and cystatin C. At physiological concentrations, the increase of total bilirubin and indirect bilirubin can reduce cystatin C.