Background/Purpose: Little is known about acute care utilization in patients with APS and/or SLE. This study focuses on hospitalizations, intensive care unit (ICU) admissions and emergency department (ED) visits, in patients with APS and/or SLE, both one year prior to and after identification of positive aPLs or diagnosis with SLE, compared to a control population.

Methods: Patients from our observational aPL/APS and SLE registries were included. Patients had persistently positive aPL (medium positive [40-80 GPU] or high positive [ >80 GPU] anticardiolipin or anti-beta-2 glycoprotein 1 or a positive lupus anticoagulant test, measured at least 12 weeks apart) and/or fulfilled ACR or SLICC SLE classification criteria. Patients diagnosed with APS clinically met revised Sapporo Criteria. The index date was defined as the date that persistently positive aPL were first identified or that SLE classification criteria were met. Acute care utilization one year prior to and after the index date was determined. Data were sourced from several provincial health-related databases in Alberta, Canada. Acute care utilization was compared to age, sex, and geographic matched controls, excluding individuals with testing for aPLs, ANA, ENA or anti dsDNA or those with any practitioner claim codes or ICD codes for SLE or APS. Controls were assigned the index date of their matched case. Descriptive statistics were used to summarize baseline demographics and acute care utilization. Conditional logistic regressions were applied to assess differences between cases and matched controls for binary outcomes, generalized linear mixed Poisson regression models for discrete count and Gamma regression models for continuous outcomes, accounting for matched pairs.

Results: 459 patients participated: 65 with APS (+/- SLE), and 440 with SLE (+/- aPL) (Table 1). There were 2,525 matched controls randomly selected. One year prior to the index date, patients with APS and/or SLE had significantly higher rates of hospitalizations compared to their respective control groups (all p < 0.0001) (24.0% in APS vs. 3.7% in controls, and 13.9% in SLE vs. 5.0% in controls). ED visits rates were also higher in APS (54.0% vs. 16.7%) and SLE (46.1% vs. 15.9%) groups. One-year post-index date, healthcare utilization remained significantly higher in patients with APS and/or SLE. Hospitalization rates rose to 42.6% in APS and 33.0% in SLE, both significantly higher than their controls (4.7% and 4.9%, respectively; p < 0.0001). SLE patients also had longer hospital stays (5.75 (3.00-9.00) vs. 2.00 (1.00-3.00) median days, p = 0.0323) and more hospitalizations (1.00 (1.00 -2.00) vs. 1.00 (1.00 -1.00), p = 0.0012). ICU admissions rates were higher in SLE patients than controls (1.03% vs. 0.07%, p = 0.0190). ED visit rates remained elevated in APS (59.3% vs. 13.4%) and SLE (47.5% vs. 14.7%) groups, with significantly higher mean visit counts in both (p = 0.0119 for APS; p < 0.0001 for SLE) (Table 2).

Conclusion: Patients with APS and/or SLE have a higher rate of hospitalizations and ED presentations compared to a control population, both one year prior to and after the first identification of positive aPLs or diagnosis of SLE.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/acute-care-utilization-in-patients-with-antiphospholipid-syndrome-and-or-systemic-lupus-erythematosus/