627. Outcomes of Military Blood Donors Screening Positive for <i>Trypanosoma cruzi</i>

Abstract Background First time blood donors at the Armed Service Blood Bank-San Antonio are screened for Trypanosoma cruzi infection with a chemiluminescent microparticle immunoassay (CMIA) followed by a confirmatory enzyme strip assay (ESA). In military populations, T. cruzi positivity on a screening test accounts for the fourth most common reason for post-donation deferral. With concerns for low positive predictive value in a low prevalence disease, this study evaluated the clinical outcomes and diagnostic work-up of blood donors who screened positive on T. cruzi CMIA testing.Table 1:Workup of 49 blood donors who screened positive for Trypanosoma cruzi infection Methods All blood donors from 2017-2022 were screened for T. cruzi antibodies with CMIA and deferred indefinitely if screening was positive, regardless of ESA result. All donors that initially screened positive for T. cruzi infection were evaluated to determine diagnostic work-up, further testing, specialty appointments seen, and final diagnosis of each case following their initial positive blood donation screen.Table 2:Clinical outcomes of 4 blood donors with positive T. cruzi screening test and confirmatory test Results Of 89,459 blood donors during the study period, 49 (57.3 per 100k donors) screened positive for Chagas disease on initial blood donation. Of those individuals, 4 (8%) had positive, 18 (36%) had indeterminate, and 30 (61%) had negative confirmatory tests. The evaluation varied significantly depending on the results of ESA testing, however there were no blood donors who met criteria for Chagas disease (Table 1). Evaluation of four donors with positive CMIA and ESA showed only one with repeat positivity on one assay, but all were ultimately deemed negative (Table 2). Conclusion While positive T. cruzi antibodies were a common reason for post-donation deferral in this cohort, there were no confirmed cases of Chagas disease, despite most patients receiving an extensive work-up. Patients with positive or indeterminate ESA received more specialty care and more confirmatory testing than those with a negative confirmatory test. This study demonstrates the need for higher specificity screening and confirmatory tests for T. cruzi in blood donors in low prevalence settings. Disclosures All Authors: No reported disclosures