Evaluation of a new chemiluminescence immunoassay for diagnosis of syphilis

Evaluation of chemiluminescence immunoassay as a screening test for syphilis on blood donor samples

BACKGROUND AND OBJECTIVE

Global re-emergence of syphilis among blood donors necessitates novel diagnostic and prevention approaches that encourage timely intervention. Thus, the present study was planned to evaluate the efficiency of Chemiluminescence immunoassay (CLIA) as a screening test for syphilis.

MATERIAL AND METHODS

This prospective cross-sectional observational study was conducted from October 2021 to September 2022. A total of 344 donors were enrolled by purposive sampling method, including additional 16 donors who were reactive by the Rapid plasma reagin test (RPR) during the study period. Data from three screening tests - RPR test, Treponema pallidum haemagglutination assay (TPHA) and CLIA for 360 blood donors were analysed. TPHA was considered the gold standard test.

RESULTS

Of the total 360 samples tested, 21 (5.8 %) were reactive by the RPR test. Of these 21 RPR reactive samples, 19 (90.5 %) were reactive by both TPHA and CLIA, while 2 (9.5 %) RPR reactive samples were non-reactive by both TPHA and CLIA. Of the remaining 339 RPR non-reactive samples, 1 (0.3 %) sample was reactive by both TPHA and CLIA, and 1 (0.3 %) was reactive by CLIA alone. CLIA was found to have sensitivity and specificity of 100 % and 99.7 % and positive predictive value (PPV) and negative predictive values (NPV) of 95.2 % and 100 % respectively, while it was 95 %, 99.4 %, 90 %, and 99.7 %, respectively, with the RPR test.

CONCLUSION

CLIA was found to have a higher sensitivity, specificity, PPV and NPV than the RPR test. Thus, CLIA can be an acceptable alternative for syphilis screening in blood donors.

Confirmation value of Western blotting in detecting anti-treponema pallidum specific antibodies with suspicious results

Background

Due to the inconsistent results of anti-treponema pallidum (TP) specific antibodies by enzyme-linked immunosorbent assay (ELISA) and Treponema pallidum granule agglutination assay (TPPA) in clinical work, there will be a certain proportion of false-positives and false-negatives depending on TPPA as confirmation results. This study aimed to evaluate the necessity of Western blotting (WB) in samples with inconsistent results in detecting anti-TP antibodies by ELISA and TPPA.

Methods

Specific anti-TP test results in our clinical laboratory were retrospectively analyzed. The specimens with a positive or a negative result, but with colored ELISA plates, were retested by TPPA. WB was used to confirm the suspicious results between ELISA and TPPA. The Chi-square test was used to analyze whether the difference was statistically significant.

Results

A total of 106,757 anti-TP specimens were screened by ELISA from August 2018 to December 2019; 3972 were retested by TPPA, and 3809 were positive by TPPA. ELISA and TPPA showed different results in 163 specimens. Among them, 29 specimens were negative and 134 were positive by ELISA; 76 were negative, 23 were positive, and 64 were “reserve” by TPPA; 93 were negative, 31 were positive, and 39 were suspicious by the WB confirmation test. Compared with WB, the difference in the results of ELISA and TPPA was statistically significant.

Conclusions

TPPA is an effective retest method for anti-TP antibody detection. If the results of anti-TP antibodies by ELISA and TPPA are inconsistent, it is necessary to use WB for confirmation.

Trial registration This retrospective analysis is in accordance with the ethical guidelines of China and approved by the second hospital of Jiaxing (jxey-2018048).

Comparative evaluation of ADVIA Centaur® XP chemiluminescence system for screening of HBV, HCV, HIV and syphilis in Indian blood donors

BACKGROUND

The introduction of chemiluminescent immunoassay (CLIA) in blood donor screening has led to a gradual replacement of enzyme-linked-immunosorbent assay (ELISA) as the former offers automation, higher sensitivity and lower turn-around-time. However, only a few CLIA platforms are used for blood donor screening in India. The present study evaluated one such newer platform viz., Adiva Centaur XP CLIA for screening of HBV, HCV, HIV and syphilis.

MATERIAL AND METHODS

Prospective comparative study wherein 4843 whole blood donors were screened for HBsAg, Anti-HCV, HIV Ag-Ab and Anti-treponemal antibodies in both Advia Centaur XP and Architect i2000SR platforms. Additional tests were performed in samples which were reactive in only one of the platforms. The sensitivity, specificity, positive predictive value, negative predictive value, accuracy, false positive rate and false negative rate of both the platforms were compared. Kappa coefficient was calculated to determine the agreement between the testing platforms.

RESULTS

The sensitivity of Advia Centaur platform for HBV, HCV, HIV and syphilis detection were 94.9 %, 100 %, 100 % and 100 % respectively as compared to 96.6 %, 100 %, 100 % and 100 % in Architect i2000SR platform. The specificity of both the platforms were 99.8-99.9 % for all the four tests. The agreement between the two platforms was almost perfect for HBV, HCV and syphilis testing; and fair for HIV testing.

CONCLUSION

The Advia Centaur CLIA platform was found to be comparable with the Architect CLIA platform for blood donor screening. Unexpected finding was the occurrence of HBV false negatives in both the platforms, possibly due to HBsAg mutations.

Performance evaluation of immunoassay for infectious diseases on the Alinity i system

Background

Although a diagnosis of infectious diseases is essential for timely treatment, the performance of diagnostic tests has been hardly evaluated due to variable results that are influenced by multiple factors in different conditions. In the present study, the performance of the Alinity i system, which is a newly developed immunoassay to diagnose infectious diseases, was evaluated.

Methods

We evaluated the precision, linearity, correlation, and carryover of 16 analytes (HAV Ab IgG, HBsAg, HBeAg, anti‐HBc, anti‐HBe, anti‐HBs, anti‐HCV, HIV Ag/Ab, EBV VCA IgM, EBV VCA IgG, EBV EBNA IgG, CMV IgM, CMV IgG, Toxoplasma IgG, Rubella IgG, and Syphilis TP) of Alinity i by comparison with ARCHITECT i2000_SR system following the rationale of the Clinical and Laboratory Standards Institute (CLSI).

Results

For quantitative tests, the coefficients of variation (CV) % of repeatability and intermediate precision were between 0% and 4.18%. The coefficients of the linearity (r²) over a widely tested analytical range were ≥ 0.990 and the correlation between Alinity i and the ARCHITECT i2000_SR system was strong (r ≥ 0.994). For qualitative tests, the agreement between Alinity i and the ARCHITECT i2000_SR system was excellent (kappa coefficient 1) with 100% sensitivity and specificity. Carryover rates for all analytes were less than 1.0% (−0.11% ~ 0.21%).

Conclusion

The Alinity i system showed good analytical performance and favorable comparability with the ARCHITECT i2000_SR. It could be suitable as a routine immunoassay analyzer for screening and diagnosis of infectious disease.

Performance of Treponema pallidum recombinant proteins in the serological diagnosis of syphilis

Syphilis serodiagnosis is challenging because distinct clinical forms of the infection may influence serological performance and discordant results between tests make clinical decisions difficult. Several recombinant Treponema pallidum-proteins have already been tested for syphilis diagnosis and they are critical to achieve high accuracy in serological testing. Our aim was to assess the varied from performance of T. pallidum-recombinant proteins TmpA, TpN17 and TpN47 for syphilis serodiagnosis. The proteins were evaluated using sera of 338 T. pallidum-negative, 173 T. pallidum-positive individuals and 209 sera from individuals infected with unrelated diseases. The diagnostic potential was validated by analysis of ROC curves. In the liquid microarray analyses, the ROC curve varied from 99.0% for TmpA and TpN17 to 100% for TpN47. The sensitivity score yielded values of up to 90% for TpN17, 100% for TpN47 and 80.0% for TmpA. The lowest and highest specificity values were presented by TpN47 (91.9%) and TmpA antigens (100%), respectively. TpN47 showed the highest accuracy score (95.5%) among all the recombinant proteins assayed. For the ELISA, the ROC curve was 97.2%, 91.8% and 81.6% for TpN17, TmpA and TpN47, respectively. TpN17 and TmpA yielded a sensitivity of 69.9%, while TpN47 obtained a value of 53.8%. Specificity was almost 100% for all three proteins. No cross-reaction was observed for TpN17 in the serum samples from non-bacterial infections. Regarding leptospirosis-positive samples, cross-reactivity score was varied from 8.6 to 34.6%. This is most probably due to conservation of the epitopes in these proteins across bacteria. The use of recombinant proteins in immunoassays for syphilis diagnosis was showed provide greater reliability to results of the treponemal assays. Despite the low sensitivity, the proteins showed high diagnostic capacity due to the AUC values found. However, an improvement in sensitivity could be achieved when antigenic mixtures are evaluated.

The analyzation and clinical evaluation of ECLIA and CMIA in the detection of Treponema pallidum

To evaluate the clinical application value of electrochemiluminescence immunoassay analyzer (ECLIA) and chemiluminescent magnetic microparticle immunoassay (CMIA) in the detection of Treponema pallidum (TP).A total of 1225 patients in Peking University Third Hospital was enrolled from June 2014 to October 2014. ECLIA and CMIA were applied to detect the serum anti-TP. The positive rate was analyzed. RIBA was taken as a golden standard to evaluate the sensitivity, the specificity, the positive predictive value, the negative predictive value, and the accuracy of ECLIA and CMIA. A correlation analysis between 2 assays was conducted, and that between assay and RIBA. We also evaluate the clinical value of TPPA in the detection of T pallidum.The positive rate of CMIA and ECLIA is 10.63% and 9.89%, respectively, showing no statistically significant difference (P > .05). For CMIA, ECLIA, and TPPA, the sensitivity is 99.16%, 99.16%, and 99.16%, the specificity is 98.99%, 99.82%, and 100%, the positive predictive value is 91.47%, 98.33%, and 100%, the negative predictive value is 99.91%, 99.91%, and 99.91%, the coincidence rate is 99.01% (Kappa = 0.895), 99.75% (Kappa = 0.997), and 99.92% (Kappa = 0.998), respectively.The result shows high correlation between ECLIA and CMIA. Both have high sensitivity and specificity and can be used as screening tests for the diagnosis of T pallidum in common condition.

Evaluation of the HISCL Anti-Treponema pallidum Assay as a Screening Test for Syphilis

The resurgence of syphilis in recent years has become a serious threat to public health worldwide, and the serological detection of specific antibodies against Treponema pallidum remains the most reliable method for laboratory diagnosis of syphilis. This study examined the performance of the recently launched HISCL anti-Treponema pallidum (anti-TP) assay as a screening test for syphilis in a high-volume laboratory. The HISCL anti-TP assay was tested in 300 preselected syphilis-positive samples, 704 fresh syphilis-negative samples, 48 preselected potentially interfering samples, and 30 "borderline" samples and was compared head to head with the commercially available Lumipulse G TP-N. In this study, the HISCL anti-TP assay was in perfect agreement with the applied testing algorithms with an overall agreement of 100%, comparable to that of Lumipulse G TP-N (99.63%). The sensitivity and specificity of the HISCL anti-TP assay were 100% (95% confidence interval [CI], 98.42% to 100%) and 100% (95% CI, 99.37% to 100%), respectively. Considering the excellent ease of use and automation, high throughput, and its favorable sensitivity and specificity, the HISCL anti-TP assay may represent a new choice for syphilis screening in high-volume laboratories.

Performance Evaluation of CLIA for Treponema Pallidum Specific Antibodies Detection in Comparison with ELISA

OBJECTIVES

In this study we aimed to evaluate the performance effects of chemiluminescence assay (CLIA) for Treponema pallidum specific antibodies detection, and to compare T. pallidum specific antibodies detection accuracy between CLIA and ELISA with TPPA (T. pallidum particle agglutination assay) as a confirmatory test.

METHODS

A total of 865 samples from suspected syphilis patients and preoperative patients were included, in which T. pallidum specific antibodies were simultaneously detected by CLIA and ELISA. Among them, 457 samples were determined by TPPA.

RESULTS

All coefficients of variation (CVs) of ELISA in high-, median-, and low-level samples were more than 5% and the maximum CV was 54.39% in the low-level sample. CVs of CLIA in different-level samples were all below 5%. Among the three assays the Spearman correlation and Kappa coefficients were 0.771 (P ≤ 0.001) and 0.854 (P ≤ 0.001, CLIA vs. ELISA), 0.806 (P ≤ 0.001) and 0.897 (P ≤ 0.001, ELISA vs. TPPA), 0.937 (P ≤ 0.001) and 0.967 (P ≤ 0.001, CLIA vs. TPPA), respectively. The area under the receiver operating characteristic curve (AUC) of CLIA was higher than that of ELISA (0.994 vs. 0.989) with TPPA as the confirmatory test. In 18 discrepant samples the consistency rate between CLIA and TPPA was elevated compared with that between ELISA and TPPA (72.22% vs. 27.78%, P = 0.008). In gray zone, the consistency rate of CLIA with TPPA was higher than that of ELISA with TPPA (90.91% vs. 41.67%, P = 0.027).

CONCLUSIONS

Compared with ELISA, CLIA is more reliable, sensitive and accurate to detect serum T. pallidum specific antibodies. In the future it may be an alternative test with higher sensitivity to ELISA.