P-543. Role of respiratory viral infections in Airflow Obstruction after Pediatric Hematopoietic Cell Transplantation

Abstract Background Respiratory Viral Infections (RVIs) in allogeneic hematopoietic cell transplant (allo-HCT) recipients can cause airflow obstruction (AFO), leading to pneumonia or death, particularly in those with preexisting conditions. Despite this risk, the impact of community-acquired RVI on PFTs in pediatric patients after HCT remains unclear. Methods This retrospective study analyzed St. Jude patients undergoing HCT between 2003-2020. Data from electronic health records included patient demographics, transplant information, microbiological results, and RVI episode information during 100 days post-HCT. AFO was defined by z-scores and FEV1/FVC ratio expressed as LLN. Baseline parameters were obtained before HCT, and Year 1 parameters within 425 days post-HCT. Spirometry measures were calculated using GLI calculator. Bivariate and multivariate logistic regression identified risk factors for airflow decline following HCT. Results A total of 397 patients were included in the study, with a median age of 12.7 years (Table 1). Approximately 13% developed RVI within the first 100 days post-transplantation. Of these, the majority (78%) required oxygen therapy (median days=7), which was significantly (P< 0.05) longer than that of individuals without viral infections (median days=5). Furthermore, patients with RVI who required oxygen were significantly (P< 0.05) more likely (14% vs 10%) to require ICU admission than those without an infection who did not require oxygen. Among patients with AFO (12%), 68% had a baseline FEV1/FVC ratio above LLN, 11% had a history of Lower Respiratory Tract Infection (LRTI), which was significantly (P< 0.05) higher as compared to those without AFO (2%). The median time from transplant to RVI was significantly shorter in patients with AFO (12 days vs 34 days). We found baseline LLN as a significant predictor for airflow decline (Table 2). However, our model (Table 2) did not find a significant association between the risk of severe airflow decline and RVI after adjusting for covariates which have been identified as risk factors for airflow decline in the literature (Figure 2). Conclusion Respiratory viral infection within 100 days of allo-HCT did not significantly affect airflow obstruction following HCT in pediatric patients. Disclosures Randall Hayden, MD, Abbott: Board Member|Abbott: Serving on the advisory board|Cepheid: Board Member|Cepheid: Serving on the advisory board|Roche Diagnostics: Advisor/Consultant|Roche Diagnostics: Board Member|Roche Diagnostics: Serving on the advisory board Gabriela Maron, MD, MS, SymBio Pharamaceuticals: Advisor/Consultant|SymBio Pharamaceuticals: Grant/Research Support