Transfusion effectiveness and clinical outcomes in acute leukemia: Do poor responders have worse outcomes?

e18614 Background: Transfusion support is essential for patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), yet most literature focuses on hemoglobin or platelet thresholds rather than transfusion effectiveness. In practice, clinicians often assume predictable post-transfusion increments even in the setting of active leukemia, inflammation or marrow failure. We evaluated transfusion response and STAT priority timing in AML and ALL to determine whether these factors were associated with length of stay (LOS) and in-hospital mortality. Methods: We conducted a retrospective cohort study of hospitalized adults (≥18 years) with AML or ALL who received RBC or platelet transfusions at a tertiary academic center from October 2022 to October 2025. Analyses were restricted to transfusion episodes with available pre- and post-transfusion lab values. Primary outcomes were transfusion response for RBCs (ΔHgb, g/dL) and platelets (Δplatelet, ×10⁹/L). Adequate response was defined as ΔHgb ≥1.0 g/dL or Δplatelet ≥10×10⁹/L. Secondary outcomes included LOS and in-hospital mortality. We used regression models to evaluate associations with STAT priority orders. Results: Among 115 patients, 544 RBC and 779 platelet transfusion episodes were evaluable. Median RBC increment was 0.8 g/dL; 39.7% achieved ≥1.0 g/dL and 18.4% showed no rise or a decrease. STAT orders were independently associated with smaller RBC (β −0.25 g/dL, p=0.016) and platelet increments (β −4.93×10⁹/L, p=0.005). Adequate RBC response was associated with shorter LOS (β −6.64 days, p<0.001), while adequate platelet response was strongly associated with lower in-hospital mortality (OR 0.62, p≈0.001). STAT priority orders were associated with shorter LOS for both RBC (β −11.82 days, p<0.001) and platelet episodes (β −13.29 days, p<0.001), with opposite mortality associations by product type, reflecting clinical acuity. Conclusions: Transfusion response in AML and ALL is variable, with fewer than half of RBC or platelet transfusions achieving expected lab increments. Adequate RBC response shortens LOS, while adequate platelet response reduces in-hospital mortality. STAT orders identify encounters with smaller increments but substantially shorter LOS, highlighting the role of clinical urgency. These findings support evaluating transfusions by “units effective” rather than “units administered.” This retrospective design limits adjustment for unmeasured clinical severity, underscoring the need for further multicenter studies. RBC Metrics Platelet Metrics Median ΔHgb (g/dL) 0.8 Median Δplatelet (×10⁹/L) 12 % Adequate response (≥1g/dL) 27.5% % Adequate response (≥10×10⁹/L) 43% % No rise or decrease 12.9% % No rise or decrease 15.6% STAT effect on ΔHgb (β,p) -0.25 (p=0.016) STAT effect on Δplatelet (β,p) -4.93 (p=0.005) Adequate response on LOS -6.64 (p<0.001) Adequate response on mortality 0.62 (p=0.001)