Increased Diagnosis of Spondyloarthritis in Female Patients Started in the Early Biologic Era

Nisha Nigil Haroon¹, Ping Li², Michael Paterson² and Nigil Haroon³, ¹Department of Medicine, University of Toronto, Toronto, ON, Canada, ²Institute of Clinical Evaluative Sciences, Toronto, ON, Canada, ³Toronto Western Research Institute, Toronto, ON, Canada

Meeting: 2014 ACR/ARHP Annual Meeting

Keywords: Ankylosing spondylitis (AS), epidemiologic methods and population studies, Health Care

Session Information

Title: Spondyloarthropathies and Psoriatic Arthritis V - Clinical Aspects and Treatment

Session Type: Abstract Submissions (ACR)

Background/Purpose

The health and economic impact of spondyloarthritis is considerable and growing. Over the past decade or more, there have been two major changes in this field that could potentially affect the diagnosis of new AS patients. The first was the introduction of Tumor Necrosis Factor inhibitors (TNFi), which dramatically changed the treatment paradigm in AS. The second was the introduction of a new entity called non-radiographic axial Spondyloarthritis (nr-AxSpA), defined based on the presence of MRI changes and HLA-B27, but without classic X-ray changes of AS. We studied the changes in incidence and prevalence of spondyloarthropathies (SpA) over time in Ontario, Canada.

Methods

We performed a population-based, retrospective cohort study on patients with SpA, age 15 or above, living in Ontario between 1995 and 2010. We used a stringent SpA definition of 2 outpatient claims within 2 years with at least one inpatient or rheumatologist claim. Incidence ratios, prevalence rates and confidence intervals were calculated using Poisson regression. The incidence of SpA in men and women were compared in the pre-biologic era (1995-2000), early biologic era (2000-2005) and late biologic era (2005-2010).

Results

A total of 21,878 SpA patients were identified. The age, sex and local health integration network (LHIN) standardized prevalence rates (per 100,000) for SpA were 79 in 1995, 132 in year 2000, 173 in 2005 and 213 in 2010. The male: female ratio was 1.7 in 1995, which progressively dropped to reach 1.25 by 2010. A significant increase in the diagnosis of female AS patients but not male patients occurred between 2000-2005. The male; female ratio in incident cases decreased from 1.3 in 1995 to 1.0-1.1 by 2005-2010. In both sexes, the incidence rates rose uniformly in all age groups (15-44 years, 45-64 years and above 65 years) with time.

Conclusion

In this large population-based study, the period specific adjusted prevalence of SpA progressively increased. More female patients were diagnosed with SpA from 2000 onwards which correlates with the introduction of TNFi therapy in AS. Thus the trend of increasing female SpA patients predates the introduction of MRI and the new ASAS classification criteria for axial SpA.

Disclosure:

N. Nigil Haroon,
None;

P. Li,
None;

M. Paterson,
None;

N. Haroon,
None.

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