Detection of anticardiolipin antibody IgG by time-resolved fluoroimmunoassay

Simultaneous detection of Mycoplasma pneumoniae IgG and IgM using dual-label time resolved fluoroimmunoassay

Anti-Mycoplasma pneumoniae (MP) IgM and IgG are useful serological markers for detection of MP infection. In this study, a simultaneous quantification of MP IgM and IgG was performed by time-resolved fluoroimmunoassay (TRFIA). The europium-labeled anti-human IgM and samarium-labeled anti-human IgG were used as tracers, and MP IgM and IgG were recognized in serum samples. After dissociating europium and samarium ions from the immune complex, their fluorescence intensity was recorded and used to calculate the concentrations. The linear range and sensitivity of detection were 2-5500 BU/mL and 0.5 BU/mL for IgM, and 1.5-1500 BU/mL and 0.2 BU/mL for IgG, respectively. The intra- and inter-assay coefficients of variation were 5.14% and 8.41% for IgM, and 5.44% and 8.76% for IgG, respectively. The recovery rate was 94.9-106.8% for IgM and 96.1-109.4% for IgG. The correlation rates of serum detection for 38 respiratory infected patients between dual-label TRFIA and ELISA were 0.9294 and 0.9366 for IgM and IgG, respectively. The coincidence rate between passive particle agglutination and TRFIA is 93.3%. Dual-label TRFIA is a sensitive and reliable technique for measuring MP IgM and IgG levels and could be useful for the early diagnosis of MP infection.

Development of a time-resolved fluorescence immunoassay for Epstein-Barr virus nuclear antigen 1-immunoglobulin A in human serum

Enzyme-linked immunosorbent assay (ELISAs) specific for Epstein-Barr virus nuclear antigen 1 (EBNA1)-immunoglobulin A (IgA) are most commonly used in the clinical diagnosis of EBV infection. But they have a low sensitivity and the enzyme-labeled antibodies are unstable. In this study, a novel immunoassay based on an indirect time-resolved fluoroimmunoassay (TRFIA) was developed. Microtiter plates were coated with recombinant EBNA1. We used Eu(3) (+)-labeled anti-human IgA as probe. The precision, sensitivity, specificity, and stability were evaluated, and comparison with traditional and commercially available ELISAs was also made. The cut-off value for our TRFIA was 2.7. Intra- and inter-assay coefficients of variation for the TRFIA were 1.56-4.99% and 3.92-6.95%, respectively; whereas those for the ELISA were 4.54-8.16% and 7.07-10.52%, respectively. Sensitivity was obviously better than traditional ELISA when diluted positive samples serially. Additionally, stability, specificity test and comparison of sensitivity and specificity between the TRFIA and commercial ELISAs all proved satisfactory. In conclusion, the results demonstrated that EBNA1 IgA TRFIA was a sensitive immunoassay and had potential value in large-scale screening of human serum samples in developing countries.

Detection of Hepatitis B Virus Large Surface Protein Using a Time-Resolved Immunofluorometric Assay

BACKGROUND

To establish a novel method based on time-resolved immunofluorometric assay (TR-IFMA) with higher sensitivity and a broader detection range for detecting serum hepatitis B virus large surface protein (L protein).

METHODS

The precision, sensitivity, specificity, coefficient of recovery, and stability of the assay were evaluated and comparison with the classical enzyme-linked immunosorbent assay (ELISA) was also executed.

RESULTS

The precision, specificity, and sensitivity of the TR-IFMA were clearly better than ELISA. Particularly, the sensitivity was 0.1 ng/ml; moreover, the specificity was 100%, 96%, 92.5%, 96.9%, 97.8%, and 100% in the sera of healthy blood donors, systemic lupus erythematosus (SLE) patients, rheumatoid arthritis (RA) patients, hepatitis C virus (HCV) patients, cytomegalovirus (CMV) infection patients, and pregnant patients, respectively. Meanwhile, we observed that the established TR-IFMA kit has a wider acceptable linear range of 0.63-10,367 ng/ml rather than the regular commercial ELISA kit having range of only 10.12-1095.9 ng/ml. Subsequently, correlation coefficient between the TR-IFMA and ELISA was 0.8009. The intra- and interassay precision rates were less than 5% for three different concentrations. The average recovery rate for L protein was 101.17%. In sum, the established assay kit performed better in terms of stability than the commercial ELISA kit.

CONCLUSION

The TR-IFMA that we developed for L protein presented a higher sensitivity and wider detecting range than regular commercial ELISA. Therefore, this TR-IFMA has promising value both in the screening of HBV and monitoring of antiviral therapy.

Detection of anti-cyclic citrullinated peptide using a time-resolved fluoroimmunoassay

In an effort to enhance the linear range of anti-CCP we developed a new immunoassay based on time-resolved fluoroimmunoassay. The precision, sensitivity, specificity, and stability of the assay were evaluated ELISA set as control. The anti-CCP IgG TRFIA kit we established had a wider detectable range than commercial ELISA ones. With regard to intra- and inter-assay precision, the TRFIA kit was better than threee commercial ELISA ones. The mean recovery rate was 101.0%. The TRFIA we developed for anti-CCP IgG detection yielded a more sensitive and reliable method for RA diagnosis and large-scale screening programs as well.