2886. Retrospective Case–Control Study of the Performance of the Karius Test, a Plasma Microbial Cell-free DNA Next-generation Sequencing test, to Detect Invasive Mold Infections in Hematopoietic Cell Transplant Recipients with Pneumonia

Abstract Background Pulmonary invasive mold infections (IMI) cause significant morbidity and mortality after hematopoietic cell transplant (HCT). Noninvasive diagnostic options are limited, particularly for non-Aspergillus (non-Asp) molds. Given differences in activity and toxicities of antifungals, early diagnosis and targeting of specific IMI is important. We evaluated the performance of the Karius Test, a plasma microbial cell-free DNA next-generation sequencing (NGS) test, for detecting IMI in HCT recipients. Methods We conducted a retrospective case–control study of 24 HCT recipients with proven non-Asp pulmonary IMI, 51 probable/proven Aspergillus pulmonary IMI, and 20 controls with nonfungal pulmonary infections. All subjects had plasma obtained within 14 days of diagnosis. Workup included bronchoalveolar lavage (BAL) and/or biopsy, with fungal stains/culture and galactomannan testing of BAL and serum. Plasma cell-free DNA was extracted and NGS performed (Karius, Redwood City, CA). Human reads were removed and remaining sequences aligned to a curated database including over 300 fungi. Organisms present above a predefined significance threshold were reported. A higher sensitivity research-use only pipeline was also used. Analysis of sequencing data was blinded to all clinical data. Results We identified pathogenic molds in 19/24 (79%) of subjects with proven non-Asp IMI, including Mucor, Rhizomucor, Scedosporium, Rhizopus, and Cunninghamella spp. In Aspergillus proven/probable IMI, A. fumigatus was identified in 13.7% (7/51) of subjects. In 3 other subjects with proven/probable aspergillosis, we also identified Rhizomucor miehei and R.pusillus, and Cunninghamella, consistent with clinical findings. The use of an optimal-sensitivity pipeline identified an additional 9 subjects with Aspergillus spp. and other pathogenic molds, increasing detection of molds to 37.3% (19/51). Specificity for molds in negative samples was 100% (20/20). Conclusion The Karius plasma NGS test is a noninvasive means of detecting IMI with high sensitivity for non-Aspmolds in HCT recipients with pulmonary disease. Further assay optimization may increase sensitivity for Aspergillus. This may be a useful adjunctive test for diagnosing IMI, and larger studies should be conducted. Disclosures All Authors: No reported Disclosures.