Session Name: Biomarkers, Immune Assessment and Clinical Outcomes
Date: Saturday, June 5, 2021
Session Time: 7:30pm-8:30pm
Presentation Time: 7:30pm-7:40pm
*Purpose: ABMR is a major cause of poor long-term graft survival. Though post-transplant monitoring of HLA DSAs can aid in risk stratification and optimizing immunosuppression, it is limited by its high cost and lack of data supporting that early detection impacts outcomes. The optimal strategy for testing for DSA is debated. Some centres use screening-bead assays before single-antigen bead (SAB) assays to assess if HLA antibodies are present, believing it is cost-effective. Others forego the screening-bead assay, using the single-antigen bead assay directly, claiming screening is not sensitive enough. We aimed to establish a testing algorithm for HLA antibodies by determining screening’s clinical utility.
*Methods: Sensitivity (Sn), specificity (Sp), positive/negative predictive values (PPV/NPV) and likelihood ratios (LR+/-) of screening were defined by comparing it to SAB assays as a gold standard for detecting HLA antibodies, and renal biopsies as a gold standard for ABMR. Data were collected from patients between 2013-2017. 688 screens and SABs from 585 patients and 97 screens and biopsies from 87 patients were included. As our study population contained patients investigated for allograft dysfunction, its prevalence of HLA antibodies and ABMR (48.1% and 24.2% respectively) was higher than reported in the general recipient population. Thus, PPV and NPV were extrapolated to the literature-reported prevalence of HLA antibodies (30%), de novo DSAs (~15%) and ABMR (~15%).
*Results: Sn for HLA antibodies was 90.6% [95% CI: 87.5%, 93.8%], NPV was 75.8% and LR- was 0.345. When extrapolated, NPV was 87.1% for HLA antibodies and 94.2% for de novo DSAs. Sn for ABMR was 91.3% [95% CI: 79.8%, 100%], NPV was 82.0% and LR- was 0.70. When extrapolated, NPV was 89.1%. Positive screens had poor clinical utility: Sp for anti-HLA antibodies was 27.2%, 95% CI [22.6%, 31.8%], PPV was 53.6% and +LR was 1.24; Sp for ABMR was 12.5%, 95% CI [4.9% to 20.1%], PPV was 25% and +LR was 1.04.
*Conclusions: High Sn and NPV of the screening-bead assay warrant its use in ruling-out anti-HLA antibodies in previously unsensitized renal transplant recipients and those with low clinical suspicion of ABMR. However, it should not be used in pre-sensitized patients or those with high clinical suspicion of ABMR.
To cite this abstract in AMA style:Agrawal A, Dijke E, Murray A, Campbell P. Utility of Screening-Bead Assay in Post-Transplant Testing of Donor-Specific Antibodies (DSA) and Antibody-mediated Rejection (ABMR) in Renal Allografts [abstract]. Am J Transplant. 2021; 21 (suppl 3). https://atcmeetingabstracts.com/abstract/utility-of-screening-bead-assay-in-post-transplant-testing-of-donor-specific-antibodies-dsa-and-antibody-mediated-rejection-abmr-in-renal-allografts/. Accessed June 16, 2021.
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