Panel Reactive Antibodies (PRA) and Donor-Specific Antibodies (DSA) in Lung Transplantation: An Indian Experience

Abstract

Purpose Lung Transplantation data on Panel Reactive Antibodies (PRA) and Donor -Specific Antibodies (DSA) in Indian Settings is limited. Panel-reactive antibody (PRA) testing estimates the percentage of potential donors to whom a recipient has HLA antibodies and approximates the risk of positive crossmatch which estimates the risk of rejection post transplant. Single antigen bead (SAB) assay is the most sensitive tool available for detecting HLA antibodies and assessing the immunological risk for organ transplant. We examined the prevalence of transplant anti-HLA antibodies at varying thresholds and evaluated the common Anti HLA antibodies correlating with AMR. Methods We performed a retrospective cohort study including all patients listed for lung transplantation between March 2017 and August 2020. Per protocol patients, transplant candidates were assessed by Luminex bead-based assays Quantitative as well as Qualitative for PRA Class I and II and Luminex bead based Single Antigen Bead assays with MFI (mean fluorescence intensity) values. Outcomes in terms of Rejection (Antibody Mediated) were taken into consideration. Results Among 135 patients, 12 (8.88%) patients showed PRA activity (Class I/II) less than 10 %, 8(5.9%) patients showed PRA activity between 11-50% and 1 patient (0.7%) had PRA activity more than 50 % pre-operatively. 1 patients (0.7%) had anti-HLA antibodies at MFI lesser than or equal to 1,000 pretransplant (group I). 24 patients (17.7%) had a history of circulating anti-HLA antibodies at MFI between 1,000 and 3,000 (group II), and 26 (19.2%) had anti-HLA antibodies at MFI greater than or equal to 3,000 (group III) and 35 (25.9%) patients had no anti-HLA antibodies detected. 3 LTx recipients developed biopsy proven AMR. Out of 3 recipients, 2 recipients had Class I anti-HLA antibodies between 1000-3000 and Class II antibodies more than 3000. HLA DQB1 was the most common Class II locus which showed MFI more than 3000 and correlated with Biopsy proven AMR in above 2 recipients. Conclusion HLA DQB1 seems to be common allele correlating with Biopsy proven AMR in our study. PRA screening (Quantitative) pre-operatively and if positive, doing Donor-Specific Antibodies assay is an important step in deciding transplant candidacy. Post operatively, doing Donor Specific Antibodies helps diagnosis of AMR in suspected cases of Rejection.