Predictors of Inpatient Transfer from the Ambulatory Day Hospital during Outpatient Allogeneic Stem Cell Transplantation

Allogeneic hematopoietic cell transplants (HCT) using ambulatory day hospital services have been shown to be a viable option for transplant programs worldwide. At the Ottawa Hospital, allogeneic transplants are routinely done through our ambulatory day hospital, with the ability to transfer patient care to an inpatient unit as needed. Factors associated with prolonged inpatient admission during these planned outpatient HCTs are mostly unknown. We describe the outcomes of patients undergoing allogeneic HCTs administered through our outpatient day hospital, and sought to identify patient, disease, and treatment characteristics associated with increased inpatient admission during transplant. We conducted a single-centre retrospective study of patients undergoing allogeneic HCT between July 2021 and July 2024. The primary outcome evaluated was the factors associated with prolonged inpatient admission days during the transplant admission. Secondary outcomes included reasons for admission, number of admissions, and overall survival . Factors associated with ≤ 5 days of inpatient admission were analyzed using a Mann-Whitney U test for continuous variables and Chi-squared test for categorical variables. Multivariate analysis to identify factors independently associated with prolonged inpatient admission (> 5 days) was performed using binary logistic regression . Among the 316 transplants during the study period, 218 (68.9%) were planned outpatient HCT. Females were 38.5% (n=84) and median(range) age at time of transplant was 58(17-75). Baseline characteristics of outpatient HCT patients are shown in Table 1. During transplant 13.3% (n=29) were never admitted, and 59.2% (n=129) had 1 admission and 27.5% (n=60) had more than 1 admission to inpatient unit. Median length of stay in the inpatient unit was 12 days and median time to first admission from start of conditioning was 8 days (Figure 1). The most common reasons for inpatient admission included febrile neutropenia in 41.5% (n=118), non-neutropenic fever in 27.5% (n=60), and severe mucositis in 9.5% (n=27) patients. Estimated OS at day+30 was 99.1% and Day+100 was 91.4%. After multivariate analysis, factors associated with ≤5 days (including 0 days) of inpatient admission were the use of RIC Fludarabine-Busulfan conditioning (HR - 2.1 (95% CI - 1.1-3.9); p = 0.032), Day 0 hemoglobin >110 g/L (HR - 2.0 (95% CI - 1.1-3.9); P = 0.033), and Day 0 albumin >35g/L (HR - 2.4 (95% CI 1.3-4.6) P = 0.008). Outpatient allogeneic HCT using daily visits to ambulatory day hospital are a feasible and safe way of performing transplants with a significant proportion of patients (13.3%) not requiring any inpatient admission. Enumerating factors associated with inpatient admissions will help to better counsel patients about their potential outcomes and to improve planning and utilization of hospital resources.

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