Lineage-specific outcomes and resource utilization associated with antiphospholipid syndrome and thrombotic microangiopathy phenotypes during U.S. cancer hospitalizations: National Inpatient Sample, 2018–2022.

Abstract

e19110 Background: Antiphospholipid syndrome (APS) and thrombotic microangiopathy (TMA) phenotypes are rare, high-acuity thrombotic syndromes observed during cancer hospitalizations; whether their inpatient impact differs between hematologic and solid malignancies at a national level remains unclear. Methods: A serial cross-sectional, hospitalization-level analysis was performed using the 2018–2022 Healthcare Cost and Utilization Project National Inpatient Sample (NIS). Adult hospitalizations with a principal malignancy were identified (ICD-10-CM C00–C97; D45–D47) and classified as hematologic malignancies versus solid tumors. APS/TMA phenotypes were defined using any-diagnosis ICD-10-CM proxies for APS/TMA (including TTP/HUS) and combined as an APS/TMA phenotype. Because the NIS lacks laboratory and medication data, exposures were analyzed as inpatient phenotypes. Outcomes included in-hospital mortality, mechanical ventilation, acute kidney injury requiring dialysis, length of stay (LOS), hospital cost (cost-to-charge ratio–adjusted), and APR-DRG severity. National estimates accounted for NIS discharge weights, hospital clustering, and stratification; outcomes were compared within lineage by APS/TMA phenotype status and across lineages among phenotype-positive admissions. Results: Among an estimated 4,808,274 cancer hospitalizations nationally, 11.8% involved hematologic malignancies and 88.2% solid tumors; the APS/TMA phenotype occurred in 0.48% of admissions. In solid tumors, APS/TMA phenotype admissions had higher mortality (8.74% vs 4.06%), mechanical ventilation (5.37% vs 2.42%), and dialysis-requiring acute kidney injury (1.19% vs 0.39%) versus non-APS/TMA admissions. In hematologic malignancies, APS/TMA phenotype admissions similarly had higher mortality (13.04% vs 6.55%), mechanical ventilation (8.33% vs 3.67%), and dialysis-requiring acute kidney injury (6.85% vs 2.26%). Among APS/TMA phenotype admissions, hematologic malignancies had longer LOS (17.69 vs 9.34 days) and higher costs ($91,950 vs $36,058) than solid tumors. Mean APR-DRG severity was higher in APS/TMA phenotype admissions for hematologic malignancies versus solid tumors (3.48 vs 3.20) and exceeded non-APS/TMA admissions in both lineages (hematologic: 2.94; solid: 2.51). Conclusions: APS/TMA phenotypes identify a rare but high-acuity subgroup of cancer hospitalizations, with greater inpatient severity and resource use in hematologic malignancies than solid tumors. These national estimates highlight lineage-specific differences in ICU-level care, dialysis use, LOS, and cost, supporting heightened surveillance and rapid escalation for phenotype-positive admissions.