Transplant-associated thrombotic microangiopathy after hematopoietic stem cell transplantation in adults: Incidence and inpatient outcomes in the U.S. National Inpatient Sample, 2016-2022.

e18570 Background: Transplant-associated thrombotic microangiopathy (TA-TMA) is one of the severe and fatal under recognised complications after hematopoietic stem cell transplantation (HSCT). Contemporary population-level estimates of incidence and inpatient outcomes are limited. Methods: We performed a retrospective cohort study using the National Inpatient Sample (NIS), 2016-2022. Adult hospitalizations with HSCT were identified using ICD 10 codes. TA-TMA was defined by ICD 10 codes during the index hospitalization. Survey weights generated national estimates. We compared demographics, length of stay (LOS), and total hospital charges (TOTCHG) by TA-TMA status using survey adjusted methods. Multivariable survey weighted logistic regression assessed associations between TA-TMA and inpatient mortality and complications, adjusting for demographic and clinical covariates. Results: An estimated 344, 905 adult HSCT hospitalizations were identified nationally, with TA-TMA occurring in 0. 3%. TA-TMA patients were younger (mean 52. 2 vs 58. 4 years) and more often female (54. 3% vs 42. 4%; p=0. 0005) ; race distribution differed (p=0. 0167), with higher proportions of Black and Hispanic patients. TA-TMA was associated with substantially greater resource utilization (LOS 19. 7 vs 7. 5 days; TOTCHG 424, 329 vs 115, 770) and higher unadjusted inpatient mortality (12. 5% vs 4. 7%; p<0. 001). Adjusted analyses showed TA-TMA was independently associated with increased inpatient mortality (aOR 2. 98, 95% CI 1. 94–4. 58) and complications, including acute kidney injury (aOR 6. 60, 95% CI 4. 92–8. 86), renal failure (2. 27, 1. 65–3. 12), dialysis (3. 23, 2. 00–5. 21), respiratory failure (2. 33, 1. 75–3. 11), liver injury (2. 06, 1. 32–3. 21), acute GVHD (6. 60, 3. 74–11. 64), and chronic GVHD (3. 78, 2. 46–5. 80). Conclusions: In a national cohort of adult HSCT hospitalizations, TA-TMA was uncommon but carried substantial excess mortality, multi organ complications, and markedly higher LOS and hospital charge. These findings underscore the need for heightened vigilance, early recognition, and standardized risk mitigation strategies for TA-TMA in HSCT recipients, such as risk stratification, aggressive management of triggers, and risk based therapeutic interventions. Outcome/ Metric No TA-TMA TA-TMA Adjusted OR (95% CI) Inpatient Mortality 4. 7% 12. 5% 2. 98 (1. 94-4. 58) Length of Stay, Days (mean) 7. 5 19. 7 Acute Kidney Injury 24. 7% 65. 4% 6. 60 (4. 92-8. 86) Renal Failure 23. 5% 35. 1% 2. 27 (1. 65-3. 12) Dialysis 3. 3% 9. 6% 3. 23 (2. 00-5. 21) Respiratory Failure 15. 8% 27. 9% 2. 33 (1. 75-3. 11) Liver Injury 6. 2% 12. 0% 2. 06 (1. 32-3. 21) Acute GVHD 1. 0% 7. 2% 6. 60 (3. 74-11. 64) Chronic GVHD 3. 9% 14. 9% 3. 78 (2. 46-5. 80) Percentages are survey weighted. Adjusted odds ratios (aORs) from survey weighted multivariable logistic regression.