Background/Purpose:   In
the last two decades, tumor necrosis factor alpha (TNFα) inhibitors have
been approved for use, and recommended as part of clinical treatment guidelines
for people with ankylosing spondylitis (AS) who fail non-steroidal
anti-inflammatory drugs and physiotherapy. Contemporary data on US
hospitalization rates, costs and length of stay in the TNFα era have not
been examined.  We sought to determine rates of hospitalization, length of stay
and hospitalization costs for patients with AS over the past two decades.

Methods:   Using the
Nationwide Inpatient Sample (NIS), we evaluated trends in hospitalizations for
AS between 1993 and 2012.  We describe rates of hospitalization and hospital charges
among US residents hospitalized with a principal diagnosis of AS using ICD-9
codes from the NIS. Analyses were performed using NIS sampling weights to
obtain US national estimates.

Results:   Rates of
hospitalization for AS as a principal diagnosis decreased from 0.4/100,000 to
0.2/100,000 over the study period, and mean length of stay also decreased from
8.9 days to 5.7 days (Table and Figure).  However, mean
hospitalization charges increased from $40,855 to $94,047, after adjustment for
inflation to 2012 US dollars using the Consumer Price Index.  The numbers of
in-hospital deaths were too low for meaningful comparisons over time. 

Conclusion:   Rates of
hospitalizations for AS and mean length of stay has decreased in AS, providing
a benchmark for the perceived improvement in AS care, which may be related to
use of biologics.  However, hospitalization charges for AS have more than
doubled from 1993 to 2012.  The reasons for the drastic increase in
hospitalization charges warrant further investigation.

Table.  Hospitalization rates, mean length of stay and mean
hospitalization charges for US residents hospitalized with a principal
diagnosis of ankylosing spondylitis between 1993 and 2013 in the Nationwide
Inpatient Sample.