(P-IN-5) Real World Anti-HCV Antibody Assay Redesign Reactivity Rate Performance Improvement Compared To Original

Background/Case Studies: Compared to diagnostic laboratory, infectious disease donor screening testing requires a uniquely designed assay with both high sensitivity to prevent transfusion transmitted infection (TTI) and high specificity to protect from unnecessary discarded donations and deferred donors. As knowledge around TTI agents evolve and technologies improve, assays must integrate these advances to improve assay performance to protect the blood supply. Our most recent anti-HCV antibody assay is a complete redesign over original anti-HCV antibody donor screening assay. It detects antibodies against a more conserved and immunogenic region of HCV NS3 thus eliminating reactivity against less conserved and immunogenic regions of HCV NS4 to improve specificity and has improved, earlier seroconversion sensitivity with enhanced signal detection through new and improved conjugates (Muerhoff AS et al. 2008, Marohnic CC et al. 2019, Tsoi, W et al. 2023).

Study

Design/Methods: RR data are transmitted to instrument central servers when connected through secure instrument manager system. European blood center customers with 12 months of original anti-HCV antibody results (pre-implementation) and 21 months of the redesigned anti-HCV antibody results (post-implementation) were included in the dataset. Pre- implementation RR was calculated (# reactive results/# results) by customer annually and monthly. The first 9 months after assay conversion were allocated as the period for validation RR and culling effect washout (not included in analysis). Post-implementation RR was calculated annually and monthly for the subsequent 12 months by customer. All data is rolling based on implementation date to minimize the impact of seasonality. A mixed effect logistic regression was performed using the repeat reactive count and total sample size as the response and the conversion phase status (0=pre-implementation, 1=post-implementation) as predictor. The coefficient of the status was evaluated.

Results/Findings: 14 centers met inclusion criteria representing 5,176,810 results (1,849,531 pre-implementation, 1,430,966 interim, 1,896,313 post-implementation). The estimation of annualized reactive rate coefficient was -0.08258, with a value of p< 0.024, which represents a 7.92% drop-in RR post-implementation relative to pre-implementation. Data is presented in table 1.

Conclusions: Assay real world data in European customers shows a statistically significant decrease in reactive rates. Of note, quality review indicates there was no increase in false non-reactive reports post-implementation. Assuming relatively equivalent prevalence in center donor population or zero prevalence, this decrease in RR translates to improvement in real world specificity. This supports appropriate classification and reduces unnecessary deferral of donors and waste of donated product.