Eu3+ /Sm3+ dual-label time-resolved fluoroimmunoassay for measurement of hepatitis C virus antibodies

Development of a time-resolved fluorescence immunoassay kit for detecting canine coronavirus and parvovirus through double labeling

OBJECTIVE

Canine enteric coronavirus (CCV) and canine parvovirus type 2 (CPV-2) are the main pathogens responsible for acute gastroenteritis in dogs, and both single and mixed infections are common. This study aimed to establish a double-labeling time-resolved fluorescence immunoassay (TRFIA) to test and distinguish CCV and CPV-2 diseases.

METHODS

A sandwich double-labeling TRFIA method was established and optimized using europium(III) (Eu3+)/samarium(III) (Sm3+) chelates. CCV/CPV-2 antigens were first captured by the immobilized antibodies. Then, combined with Eu3+/Sm3+-labeled paired antibodies, the Eu3+/Sm3+ fluorescence values were detected after dissociation to calculate the CCV/CPV-2 ratios. The performance, clinical performance and methodology used for laboratory (sensitivity, specificity, accuracy and stability) testing were evaluated.

RESULTS

A double-label TRFIA for CCV and CPV-2 detection was optimized and established. The sensitivity of this TRFIA kit was 0.51 ng/mL for CCV and 0.80 ng/mL for CPV-2, with high specificity for CCV and CPV-2. All the accuracy data were less than 10%, and the recovery ranged from 101.21 to 110.28%. The kits can be temporarily stored for 20 days at 4 °C and can be stored for 12 months at temperatures less than - 20 °C. Based on a methodology comparison of 137 clinically suspected patients, there was no statistically significant difference between the TRFIA kit and the PCR method. Additionally, for CCV detection, the clinical sensitivity was 95.74%, and the clinical specificity was 93.33%. For CPV-2 detection, the clinical sensitivity was 92.86%, and the clinical specificity was 96.97%.

CONCLUSION

In this study, a double-label TRFIA kit was prepared for CCV and CPV-2 detection with high laboratory sensitivity, specificity, accuracy, stability, clinical sensitivity and specificity. This kit provides a new option for screening/distinguishing between CCV and CPV-2 and may help improve strategies to prevent and control animal infectious diseases in the future.

Determination of serum CA724 levels using fluorescence immunochromatography

BACKGROUND

Carbohydrate antigen 724 (CA724) is a sensitive and specific indicator for multiple malignant tumors. The aim of this study was to establish a Eu-time resolved fluorescence immunochromatography (Eu-TRFICO) method for quantitative detection of CA724 in serum.

METHODS

Eu-TRFICO strips were optimized and assembled. The sensitivity, specificity and precision were evaluated using CA724 standard dilutions and matrix serum. Meanwhile, the reference interval, comparison, and sensitivity/specificity were performed using clinical negative/positive gastric cancer serum samples.

RESULTS

The standard curve equation was y = 9.869 x - 154.12 (R2 = 0.993), and the sensitivity was 0.42 U/mL. The common interferents in serum could not affect the quantitative results with low cross-reactivities (all no more than 1.09%). All average recoveries of the intra- and interbatch ranged from 102.38 to 106.40%, and all CVs were below 10%. The reference interval of the healthy subjects was < 4.68 U/mL and the reference interval of the subjects with grade I/II gastric cancer was > 9.54 U/mL. Additionally, a high Pearson r (0.9503) and sensitivity/specificity (92.86%/94.20%) were obtained.

CONCLUSION

This study prepared Eu-TRFICO strips with high sensitivity, specificity, precision and satisfactory clinical testing performance, which provides more options for clinical quantitative and convenient testing of CA724.

A new method for screening acute/chronic lymphocytic leukemia: dual-label time-resolved fluorescence immunoassay

Background

Lymphocytic leukemia (LL) is a primary malignant tumor of hematopoietic tissue, which seriously affects the health of children and the elderly. The study aims to establish a new detection method for screening acute/chronic LL using time-resolved fluorescence immunoassay (TRFIA) via quantitative detection of S100 calcium binding protein A8 (S100A8) and leucine-rich alpha-2-glycoprotein 1 (LRG1) in serum.

Methods

Here a sandwich TRFIA was optimized and established: Anti-S100A8/LRG1 caputre antibodies immobilized on 96-well plates captured S100A8/LRG1, and then banded together with the anti-S100A8/LRG1 detection antibodies labeled with Europium(III) (Eu³⁺)/samarium(III) (Sm³⁺) chelates. Finally time resolved fluorometry measured the fluorescence intensity.

Results

The sensitivity of S100A8 was 1.15 ng/mL(LogY = 3.4027 + 0.4091 × LogX, R² = 0.9828, P < 0.001, dynamic range: 2.1–10,000 ng/mL), and 3.2 ng/mL for LRG1 (LogY = 3.3009 + 0.4082 × LogX, R² = 0.9748, P < 0.001, dynamic range: 4.0–10,000 ng/mL). The intra-assay and inter-assay CVs were low, ranging from 5.75% to 8.23% for S100A8 and 5.30% to 9.45% for LRG1 with high specificity and affinity in serum samples. Bland–Altman plots indicated TRFIA and ELISA kits have good agreement in clinical serum samples. Additionally, the cutoff values for S100A8 and LRG1 were 1849.18 ng/mL and 588.08 ng/mL, respectively.

Conclusion

The present TRFIA method could be used for the quantitative detection of S100A8 and LRG1 in serum, and it has high sensitivity, accuracy and specificity. Clinically, this TRFIA method could be suitable for screening of LL via the quantitative detection of S100A8 and LRG1.

Establishment of a time‐resolved immunoassay for acute kidney injury based on the detection of Kim‐1

Aim

Methods

Results

Conclusion

Establishment and Clinical Application of a Highly Sensitive Time-Resolved Fluorescence Immunoassay for Tumor-Associated Trypsinogen-2

To establish a rapid and highly sensitive assay for tumor-associated trypsinogen-2 (TAT-2) based on the time-resolved fluorescence immunoassay (TRFIA) and evaluate its potential clinical value in patients with lung cancer. The double-antibody sandwich method was used in detecting TAT-2 antigen concentrations, and two types of TAT-2 antibodies (coating antibodies and Eu³⁺ labeled antibodies) were used. A TAT-2-TRFIA method was then established, evaluated, and used in detecting the serum TAT-2 levels of healthy subjects and patients with lung cancer. The linear range of the TAT-2-TRFIA method was 1.53-300 ng/mL, the intra-assay coefficient of variation (CV) were between 1.67% and 8.42%, and the inter-assay CV were between 4.29% and 11.44%. The recovery rates of TAT-2-TRFIA were between 99.17% and 107.06%. The cross-reactivities of trypsin and T-cell immunoglobulin mucin 3 were 0.02% and 0.82%, respectively. The serum TAT-2 levels of patients with lung cancer were higher than those of healthy subjects (P < 0.001). Combined with TAT-2, the sensitivity and specificity of CEA and CA-125 for lung cancer improved significantly. Conclusion: We successfully established a highly sensitive TAT-2-TRFIA method, which was able to facilitate the timely diagnosis of lung cancer.

Development of a time-resolved fluorescence immunoassay based on immunomagnetic beads for gastrin-17

OBJECTIVE

In this study, a novel, simple, and rapid immunoassay for the determination of gastrin-17 (G-17) in human serum was established by combining immunomagnetic beads with time-resolved fluorescence immunoassay (TRFIA).

METHODS

Immunomagnetic beads were coated with anti-G-17 M01 antibody, anti-G-17 M02 antibody was labeled with Eu³⁺ chelates. The concentration of G-17 in the serum was detected with the double-antibody sandwich method.

RESULTS

The limit of background(LOB), limit of detection (LOD), and limit of quantification (LOQ) were 0.09, 0.104, and 0.39 pmol/L, respectively. The detection range of G-17-TRFIA was 0.39-100 pmol/L. The average intra- and inter-assay coefficients of variation (CV) were 5.95%-9.07% and 6.09%-8.14%, respectively. The recoveries for the serum samples ranged from 94.70% to 100.95%. The specificity of our G-17-TRFIA was acceptable. The correlation coefficient between G-17-TRFIA and commercial G-17-ELISA methods was R² = 0.9092.

CONCLUSIONS

A novel G-17-TRFIA detection method was successfully established to provide a reference for the early diagnosis of patients with atrophic gastritis in clinical research.

Soluble Tim3 detection by time-resolved fluorescence immunoassay and its application in membranous nephropathy

Background

We aimed to develop a time‐resolved fluorescence immunoassay (TRFIA) for detecting soluble T‐cell immunoglobulin and mucin domain 3 (sTim3) in serum samples and to demonstrate a preliminary application of this method in membranous nephropathy (MN).

Methods

sTim3 TRFIA was developed, and the sTim3 concentration in the serum of patients with MN and healthy individuals was detected using a sandwich method.

Results

The sensitivity of the developed sTim3 TRFIA was 0.66 ng/mL, higher than that of an enzyme‐linked immunosorbent assay (ELISA) (1.11 ng/mL). The detection range was 0.66‐40 ng/mL. The intra‐assay coefficient of variation (CV) for sTim3 was 1.64%‐4.68%, and the inter‐assay CV was 5.72%‐9.32%. The cross‐reactivity to interleukin 6 (IL‐6) and kidney injury molecule 1 (KIM‐1) was 0.25% and 0.04%, respectively. The average recovery was 105.26%. The sTim3 concentration in patients with MN was considerably higher than that in healthy individuals (P < .001). The sTim3 concentration in the serum of patients with MN was significantly increased from G1 to G4 based on the Jonckheere‐Terpstra test (P < .001). Thus, we used sTim3 as a diagnostic indicator for distinguishing between healthy individuals and patients with MN as well as between different stages of MN.

Conclusion

We successfully established TRFIA to detect sTim3 in serum. We then applied this method to patients with MN, demonstrating for the first time that TRFIA is a valid diagnostic tool to detect sTim3 in serum.

Eu3+ /Sm3+ dual-label time-resolved fluoroimmunoassay for measurement of hepatitis C virus antibodies

AIM

To develop a new immunoassay based on the time-resolved fluorescence immunoassay (TRFIA) system for the simultaneous measurement of IgM and IgG antibodies to HCV.

METHODS

Coated recombinant HCV antigens and Eu³⁺ -labeled IgM and Sm³⁺ -labeled IgG antibodies were prepared. HCV-IgM/IgG TRFIA was established and optimized, followed by a methodological assessment. Data were expressed as x ¯ +SD and analyzed using the SPSS 13.0 software. The percentile method was used to calculate cutoff values.

RESULTS

The detection sensitivities of HCV-IgM and HCV-IgG were 0.06 S/CO and 0.15 S/CO, respectively. There was a good linear response from 1:40 to 1:40 960 for HCV-IgM and 1:20 to 1:40 960 for HCV-IgG, when samples strongly positive for HCV-IgM and HCV-IgG were serially diluted from 1:10 to 1:81 920. The average intra-assay coefficients of variation (CV) for HCV-IgM and -IgG were 3.45% and 3.71% and the inter-assay coefficients of variation (CV) were 6.49% and 6.79%, respectively. When HCV-negative/positive sera were tested by ELISA and using established kits, the negative, positive, and total conformity rates for HCV-IgM were 93.3% (28/30), 100% (25/25), and 96.4% (53/55), and those for HCV-IgG were 93.3% (28/30), 100% (35/35), and 96.9% (63/65), respectively. Additionally, the established kit exhibited good stability, with declines in fluorescence values to 11.1% and 9.5%, respectively, after storage at 37°C for 7 days.

CONCLUSION

We established a dual-label HCV-IgM/IgG TRFIA assay with a wide detection range, high specificity, high sensitivity, good stability, and good clinical value for the simultaneous measurement of HCV-IgM and HCV-IgG titers in a single test.