Impact of interhospital transfer on inpatient outcomes in Acute Myeloid Leukemia

Abstract Background: Acute myeloid leukemia (AML) frequently requires urgent inpatient management, and interhospital transfers may delay definitive care or reflect higher disease acuity. However, outcomes for transferred AML patients remain poorly characterized. This study aimed to compare inpatient outcomes between AML patients directly admitted to the hospital and those transferred from another acute care facility. Methods: We performed a weighted retrospective cohort study using the National Inpatient Sample (NIS) from 2016 to 2022, analyzing adult hospitalizations with a primary or secondary diagnosis of acute myeloid leukemia (AML). Patients were stratified by admission type: direct admission versus interhospital transfer. The primary outcome was in-hospital mortality. Secondary outcomes included length of stay (LOS), total hospital charges, receipt of inpatient chemotherapy, need for packed red blood cell (pRBC) transfusion, and inpatient complications, including acute kidney injury (AKI), disseminated intravascular coagulation (DIC), febrile neutropenia, and sepsis. We used multivariable logistic regression for binary outcomes and linear regression for continuous outcomes, adjusting for demographics (age, sex, race/ethnicity), hospital characteristics (region, bed size, teaching status), and comorbidities. Discharge weights were applied to generate nationally representative estimates. Statistical significance was defined as p < 0.05. Results: Among 122,855 weighted AML hospitalizations, 13,985 (11.3%) were interhospital transfers. Transferred patients were slightly more likely to be male (56.6% vs. 54.1%, p = 0.014) and more frequently identified as White (76.2% vs. 72.0%, p < 0.001), while Hispanic (7.2% vs. 9.8%) and Asian (2.4% vs. 4.7%) patients were less represented in the transfer group. The mean age was similar between groups (62.9 vs. 62.5 years, p = 0.2). In-hospital mortality was significantly higher in transferred patients compared to those directly admitted (15.3% vs. 7.4%, p < 0.001), with an adjusted odds ratio (aOR) of 2.16 (p < 0.001). Transferred patients had longer hospitalizations (mean LOS: 16.87 vs. 11.05 days, p < 0.001) and higher total hospital charges ($255,690 vs. $166,775, p < 0.001). After adjustment, interhospital transfer was associated with an increase of 5.83 days in LOS and $89,299 in hospital charges (both p < 0.001). Transferred patients were significantly less likely to receive inpatient chemotherapy (5.9% vs. 19.2%, adjusted decrease of 75.2%, p < 0.001). The need for packed red blood cell transfusion was slightly higher in transferred patients (27.1% vs. 25.5%, p = 0.013). Complications were more frequent among transferred patients, including AKI (33.1% vs. 23.3%, adjusted increase of 55.9%, p < 0.001), DIC (5.8% vs. 1.5%, adjusted increase of 398.8%, p < 0.001), febrile neutropenia (36.4% vs. 31.4%, adjusted increase of 24.6%, p < 0.001), and sepsis (21.9% vs. 18.4%, adjusted increase of 26.9%, p < 0.001).Conclusion: In this large, nationally representative analysis of AML hospitalizations, patients transferred from another hospital experienced significantly higher inpatient mortality, longer hospital stays, greater healthcare costs, and increased complication rates compared to those directly admitted. They were also markedly less likely to receive inpatient chemotherapy. These findings highlight the vulnerability of transferred AML patients and emphasize the importance of timely initiation of care and improved coordination during interhospital transfers.