Emergency presentation as a diagnostic failure phenotype in ovarian cancer: A National Inpatient analysis (NIS 2016–2023).

e17575 Background: Ovarian cancer is generally diagnosed and managed through outpatient care pathways, yet a substantial proportion of patients are hospitalized through non-elective admission. Framing the emergency presentation itself as a care-delivery phenotype enables identification of system-level diagnostic failure patterns and high-risk inpatient trajectories. Methods: A survey-weighted analysis of the National Inpatient Sample (NIS) 2016–2023 was performed. Adult ovarian cancer hospitalizations were identified using ICD-10-CM C56* in any diagnosis position. The exposure was non-elective vs elective admission using NIS elective status. Acute organ failure markers included sepsis (A40/A41 or R65.20/R65.21), shock (R57*), acute kidney injury (N17*), and respiratory failure (J96*). Outcomes were in-hospital mortality, ICU-level care proxy (sepsis, shock, or respiratory failure), major complications (sepsis/shock/AKI/respiratory failure), failure-to-rescue (mortality among hospitalizations with major complications), length of stay (LOS), and hospitalization cost/charges. Survey-weighted multivariable models adjusted for demographics, payer, ZIP income quartile, weekend admission, hospital characteristics, and year. Results: The weighted cohort comprised 465,875 ovarian cancer hospitalizations, of which 70.5%were nonelective. Overall, in-hospital mortality was 4.82%. Compared with elective admissions, nonelective admissions had higher mortality (6.08% vs 1.82%), ICU-level care proxy use (24.3% vs 5.6%), and major complications (39.4% vs 12.1%), with marked enrichment of acute organ failure at presentation, including sepsis (14.3% vs 2.1%), acute kidney injury (25.2% vs 8.6%), and respiratory failure (13.7% vs 3.6%). Among admissions with major complications, mortality was higher with a non-elective presentation (12.7% vs 8.6%), indicating a failure-to-rescue gap. After adjustment, nonelective admission remained independently associated with higher odds of in-hospital mortality (aOR 3.11, 95% CI 2.67–3.62), ICU-level care (aOR 4.70, 95% CI 4.41–5.00), major complications (aOR 4.17, 95% CI 3.98–4.37), and failure-to-rescue (aOR 1.58, 95% CI 1.37–1.82), as well as longer length of stay (+0.98 days). Mean hospitalization cost and charges were lower among non-elective admissions ($18,980 vs $25,189 and $67,250 vs $83,336), reflecting less planned oncologic care but greater acute care intensity. Conclusions: In contemporary U.S. inpatient care, most ovarian cancer hospitalizations occur through nonelective admission, defining a high-risk diagnostic failure phenotype with higher mortality, ICU escalation, major complications, and failure-to-rescue. This framework provides a scalable approach to benchmark emergency presentation and identify system-level opportunities to improve ovarian cancer care.