Background/Purpose: Little is known about inpatient epidemiology, economic burden and resource utilization of patients with ankylosing spondylitis (AS). The current study aims to describe those characteristics using a nationwide database.

Methods: Patients with AS were identified from the National Inpatient Sample (NIS), the largest inpatient database in the United States (US) consisting of over 4,000 non-federal acute care hospitals, using ICD-10 CM codes. The rest of patients in the database without diagnostic codes for AS were used as comparators. Data on demographics, reasons for hospitalization, length of stay, mortality, morbidity and total hospitalization charges were extracted and compared between patients with and without AS. A multivariate logistic regression model was constructed to adjust for confounders. All analyzed data was extracted from the database of the year 2018.

Results: A total of 19,130 admissions with AS were identified. The inpatient prevalence of AS was 53.9 cases per 100,000 admissions. Sepsis (27.4%), hip and knee arthroplasty (18.8%), pneumonia (7.5%), acute kidney injury (6.8%) and non-ST elevated myocardial infarction (6.2%) were the most common reasons for hospitalization. After adjusting for potential confounders, hospitalizations among patients with AS were significantly associated with longer length of stay (0.37 more days; 95% confidence interval (CI), 0.44 – 0.89) and risk for admission to intensive care unit with adjusted odds ratio (aOR) of 1.23 (95% CI, 1.11 – 1.37). Other inpatient outcomes, including inpatient mortality, shock and multiorgan failure were not significantly different between patients with and without AS. Hospitalizations of patients with AS were associated with higher cost as demonstrated by an adjusted additional mean of $4,685 (95% CI, $3,715 – $5,655) for total hospital cost and an adjusted additional mean of $19,097 (95% CI, $12,675 – $25,519) for total hospitalization charges when compared to patients without AS.

Conclusion: Inpatient prevalence of AS was higher than what would be expected from prevalence in general population. Infection and arthroplasty were the main reasons for the need for inpatient care. Hospitalizations of patients with AS were associated with longer length of stay, need for admission to ICU and cost.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/inpatient-epidemiology-and-resource-utilization-of-ankylosing-spondylitis-national-inpatient-sample-2018/