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True-positive reflex threshold value for HCV antibody screening test
Ainulkhir Hussin1, Rusmah Yusof1, Mohd Yusof Nor Rahim1
1Department of Pathology, Queen Elizabeth Hospital, Ministry of Health, Kota Kinabalu, Sabah, Malaysia.
Insights
Determining the optimal signal-to-cut-off ratio for the ABBOTT ARCHITECT i2000SR immunoassay is crucial for accurate anti-HCV screening. An optimal ratio of 5.05 was identified, demonstrating high sensitivity and specificity for reliable results.
Area of Science:
- Clinical Diagnostics
- Immunology
- Hepatology
Background:
- The Centre for Disease Control and Prevention recommends signal-to-cut-off (S/Co) ratios for supplemental testing in anti-HCV screening.
- Accurate interpretation of immunoassay results is vital for effective Hepatitis C Virus (HCV) detection.
Purpose of the Study:
- To determine the optimal true-positive signal-to-cut-off ratio for the ABBOTT ARCHITECT i2000SR immunoassay.
- To validate this ratio using reference and line immunoassay (LIA) tests for anti-HCV screening.
Main Methods:
- Analysis of 13,240 specimens using the ARCHITECT i2000SR immunoassay.
- Application of Serodia® HCV particle agglutination (HCV-PA) assay as a reference test for reactive specimens (S/Co ratio ≥ 1.00).
- Receiver operating characteristic (ROC) curve analysis to determine optimal S/Co ratio and performance characteristics, followed by validation with a HCV-LIA test.
Main Results:
- ROC analysis identified an optimal S/Co ratio of 5.05, yielding the highest Youden's Index (0.89).
- This ratio achieved a sensitivity of 93.1% and specificity of 96.0%.
- Validation using LIA confirmed high accuracy (91.8%), sensitivity (92.0%), and specificity (91.7%).
Conclusions:
- The established optimal S/Co ratio of 5.05 for the ARCHITECT i2000SR immunoassay demonstrates high diagnostic performance.
- This validated ratio can be reliably employed in routine anti-HCV screening protocols.
- The findings support the use of this specific S/Co ratio for improved accuracy in HCV diagnostics.
Introduction:
The use of a signal-to-cut-off ratio has been recommended by the Centre for Disease Control and Prevention to determine the need for further validation using a supplemental test. In this study, we aimed to determine the optimal true-positive signal-to-cut-off ratio for the ABBOTT ARCHITECT i2000SR immunoassay (Abbott Laboratories, Illinois, USA), using the Serodia® HCV particle agglutination (HCV-PA) assay (Fujirebio Inc, Tokyo, Japan) as the reference test for anti-HCV screening.
Methodology:
We analysed a total of 13,240 specimens using the ARCHITECT i2000SR immunoassay and subsequently subjected all the reactive specimens with a signal-to-cut-off ratio ≥ 1.00 (n = 267) to the Serodia® HCV-PA reference assay. Receiver operating characteristic (ROC) curve analysis was carried out and performance characteristics for each signal-to-cut-off ratio were determined. The selected signal-to-cut-off ratio value was then assessed using a line immunoassay (LIA) test.
Results:
ROC curve analysis determined that the optimal signal-to-cut-off ratio was 5.05, which gave the highest Youden's Index (J) value of 0.89, with a sensitivity of 93.1% (88.9-97.2), a specificity of 96.0% (92.4-99.4), a positive predictive value of 96.4% (93.3-99.5), and a negative predictive value of 92.2% (87.5-96.8). Validation of the optimal S/Co value using the LIA test yielded an accuracy of 91.8%, with sensitivity and specificity values of 92.0% and 91.7%, respectively.
Conclusions:
The optimal signal-to-cut-off ratio value for the ARCHITECT i2000SR immunoassay, which was determined using HCV-PA assay as the reference test and validated using a HCV-LIA assay, showed high sensitivity and specificity, and may be used in routine anti-HCV screening.
