Quantitation of estradiol by competitive light-initiated chemiluminescent assay using estriol as competitive antigen

Improved Sensitivity and Wide Range Detection of Small Analytes Using a Two-Antigen-Combined Competitive Immunoassay

Competitive immunoassays have unique advantages in the detection of small molecules and are widely used in clinical practice. However, the concentrations of some analytes usually vary greatly among different populations, which makes it difficult to balance the sensitivity and detection range of competitive immunoassays. Studies have shown that using haptens with weaker affinity for specific antibodies as competitive antigens can help improve the sensitivity of the method. Here, we developed a competitive light initiated chemiluminescence assay based on the combination of antigens with different affinities, which has high sensitivity and wide detection range. As a proof of concept, estradiol was used as the analyte. After the mixing ratio was optimized, the two labeled haptens played different competitive roles due to the different concentrations of estradiol to be tested, which improved the sensitivity of estradiol detection, while ensuring a certain detection range. The limit of detection of this method was 5.30 pg/mL, which is lower than most current estradiol immunoassay kits. Good linearity (R 2 = 0.9902) was obtained between estradiol concentrations of 17.07-2376.22 pg/mL. This study provides a new solution for the detection of small molecule biomarkers with a large concentration span, which also has considerable potential in other immunological detection methods.

Light-initiated chemiluminescent assay of 17β-estradiol metrological traceability system established by manufacturer according to ISO17511:2020 and basic performance evaluation performed by clinical end-users

Background

In order to ensure the accuracy of the product, we established 1^st model of metrological traceability hierarchy for light‐initiated chemiluminescent assay (LICA) of 17β‐estradiol (E₂) at the manufacturer, based on International Organization for Standardization (ISO) 17511:2020. Moreover, we verified/validated the basic performance (such as matrix effect and long‐term stability of end‐user IVD MD calibrator, precision, linearity interval, accuracy/ trueness, and detection capability) at the clinical end‐user.

Methods

Human serum samples were used in this study. E₂ was detected by mass spectrometry (MS) and LICA. The metrological traceability of LICA for E₂ was established according to ISO 17511: 2020 standards, and pools of human samples were used as the m.3. secondary calibrator. Precision was validated according to Clinical and Laboratory Standards Institute (CLSI) EP05‐A3. The linear interval was verified according to CLSI EP06‐ED2. Comparison of accuracy and trueness of E₂ with MS and Roche according to CLSI EP09‐A3. The detection capability was validated according to EP17‐A2. Matrix effect and long‐term stability evaluation of end‐user IVD MD calibrator were carried out according to CLSI EP14‐A2, EP25‐A. Statistical software was used for data analyses.

Results

The use of pools of human samples and fine adjusting calibrators ensured the accuracy of end‐user test results. The metrological traceability of LICA for E₂ was established. It showed excellent precision, meeting the requirements of allowable imprecision (7.5%). The allowable deviation from linearity (ADL) of 5% was allowed to show a good linear interval (12.52–4167.25 pg/ml). The accuracy/ trueness was verified, and relative deviation in the medical decision level met the performance specification of 10.03% compared with MS or Roche. The validated limit of blank, limit of detection, and limit of quantitation of E₂ were 4.95 pg/ml, 8.93 pg/ml, and 9.88 pg/ml, respectively (the allowed imprecision is 20.00%). The interference rate of E₂ ranged from −5.5% to 6.6%.

Conclusion

LICA showed high sensitivity, high specificity, excellent precision, wide linearity interval, IVD MD calibrator has long‐term stability, and no matrix effect. The metrological traceability of E₂ established by using pools of human samples as M.3. can deliver accuracy to the end‐user IVD MD and show good consistency with MS and Roche.

Performance characteristics of the light-initiated chemiluminescent assay for quantitative determination of progesterone

Background

To study the performance of quantitative determination of progesterone by light-initiated chemiluminescent assay (LICA).

Methods

Clinical samples of serum were used for detection of progesterone by LICA. The precision study was performed according to Clinical and Laboratory Standards Institute (CLSI) EP15-A3, the linear range validation was performed according to CLSI EP06-A, accuracy was evaluated according to CLSI EP9-A3, and the performance of detection capability was confirmed according to CLSI EP17-A2. All data were analyzed using SPSS software. Function regression analysis was performed by OriginPro software.

Results

The LICA-800 system exhibited low coefficients of variation (CVs) and high reproducibility, and the calculated synthetic CV was 2.16%. The access progesterone assay showed excellent linearity in the assay measuring range (0.37–40 ng/mL) using the polynomial regression method in accordance with CLSI EP06-A. Bias assessment was used to verify accuracy, and the percentage deviation met the quality requirements of the laboratory’s allowable deviation of 10.00%. In terms of the detection capability of LICA, the calculated limit of blank (LoB) was 0.046 ng/mL, limit of detection (LoD) was 0.057 ng/mL, and the limit of quantitation (LoQ) value was 0.161 ng/mL.

Conclusions

The competitive LICA provided a highly sensitive, accurate and precise method for measuring serum progesterone level.

Six Decades of Research on Human Fetal Gonadal Steroids

Human fetal gonads acquire endocrine steroidogenic capabilities early during their differentiation. Genetic studies show that this endocrine function plays a central role in the sexually dimorphic development of the external genitalia during fetal development. When this endocrine function is dysregulated, congenital malformations and pathologies are the result. In this review, we explain how the current knowledge of steroidogenesis in human fetal gonads has benefited from both the technological advances in steroid measurements and the assembly of detailed knowledge of steroidogenesis machinery and its expression in human fetal gonads. We summarise how the conversion of radiolabelled steroid precursors, antibody-based assays, mass spectrometry, ultrastructural studies, and the in situ labelling of proteins and mRNA have all provided complementary information. In this review, our discussion goes beyond the debate on recommendations concerning the best choice between the different available technologies, and their degrees of reproducibility and sensitivity. The available technologies and techniques can be used for different purposes and, as long as all quality controls are rigorously employed, the question is how to maximise the generation of robust, reproducible data on steroid hormones and their crucial roles in human fetal development and subsequent functions.

Comparison and evaluation of Abbott chemiluminescent microparticle immunoassay and ChIVD light-initiated chemiluminescent assay in the detection of Treponema pallidum antibody

Background

Laboratory tests play an important role in the diagnosis of syphilis. This study aimed to compare and assess the performance of the Abbott chemiluminescent microparticle immunoassay (CMIA) and the ChIVD light‐initiated chemiluminescent assay (LICA) in the detection of Treponema pallidum (TP) antibody.

Methods

A total of 10 498 serum samples were detected with two assays, and the Treponema pallidum particle agglutination assay (TPPA) and recombinant immunoblot assay (RIBA) methods were used for confirmation. The sensitivity, specificity, positive predictive value, and negative predictive value of the Abbott CMIA and ChIVD LICA were calculated. The coincidence rate between two assays was also evaluated. The causes of false positive and false negative of two assays were studied.

Results

For the Abbott CMIA and ChIVD LICA, the sensitivity was 94.44% and 98.15%, the specificity was 99.89% and 99.81%, the positive predictive value was 93.29% and 88.83%, and the negative predictive value was 99.91% and 99.97%, respectively. The coincidence rate between Abbott CMIA and ChIVD LICA was 99.26%, and κ value was .790. The disease of infertility, hypertensive disease, liver disease, and cancer were the common causes of false positive in both assays, while infertility was also the main reason lead to false negative.

Conclusion

Our results demonstrated that the Abbott CMIA and ChIVD LICA generally had high sensitivity and specificity and therefore may be suitable for the detection of TP antibody and screening for syphilis.

Quantitation of estradiol by competitive light-initiated chemiluminescent assay using estriol as competitive antigen

Background

Light‐initiated chemiluminescent assays (LICA) are homogeneous assays that are sensitive, specific, and free of separation and washing steps and have high throughput and high precision.

Methods

In this research, we developed a competitive method by LICA to achieve accurate quantification of estradiol (E2) in human serum. E2 competed with estriol (E3) for binding to anti‐human E2 antibodies. E3 was linked to biotin via bovine serum albumin as a linker. As this assay used competition between the labeled tracer and the analyte, an increase in E2 concentration will cause a signal decrease.

Results

The expected detection range of E2 was 20‐5000 pg/mL. The analytical and functional sensitivities were 7.16 and 13.7 pg/mL, respectively. The intra‐ and inter‐assay coefficients of variation were both below 15%, and the recovery rate ranged from 97.5% to 106.8%. The interference rates ranged from −3.6% to 5.4% and met detection requirements for E2 in hyperbilirubinemia, hemolysis, and lipemia in clinical samples. In addition, the cross‐reactivity rates between E2 and structural analogs and some reproductive hormones varied from 1.9% to 10.6% which showed that LICA is highly specific for E2. Moreover, our results showed high accordance with the IMMULITE 2000 (y = 0.6695x + 47.92, r² = .843) and VIDAS systems (y = 1.099x − 821.5, r² = .9392).

Conclusion

Our data show that the LICA, which is easy to automate, is a promising technique for quantification of E2 in human serum and could be used for clinical detection.