SAN FRANCISCO, CA—Disease severity and disability scores are significantly higher among women than men at initiation of ankylosing spondylitis (AS) treatment with tumor necrosis factor (TNF) blockers, according to a study reported at the 2015 ACR/ARHP Annual Meeting.

“Overall, at anti-TNF initiation, female AS patients experience greater disease activity relative to men at initiation of biologic therapy,” reported lead study author Michael Starr, MD, of the Rheumatology Department, McGill University in Montreal, Quebec, Canada, and coauthors.

“Whether this represents a gender bias in prescribing, concomitant fibromyalgia, [or] a gender-based difference in the acceptance of biologic treatment or disease assessment, requires additional research,” he said.

Ankylosing spondylitis is two to three times more prevalent among men than women, Dr. Starr said. “Recent studies have suggested that clinical differences [also] exist between genders with women experiencing a higher burden of disease,” Dr. Starr noted.

To identify gender differences in this disease and its treatment, the authors analyzed data from routine clinical practice in Canada using the prospective Biologic Treatment Registry Across Canada (BioTRAC) database of patients starting biologic treatment with infliximab (IFX; 65.1%) or golimumab (GLM; 34.9%) for AS. Analysis included data for a total of 539 patients administered IFX who were enrolled in the registry since 2002, or GLM since 2010.

Baseline values at enrollment and 12-month followup values were analyzed. 

“The majority of patients were male (61.8%),” the authors reported. “Mean age and disease duration were comparable between genders for both GLM and IFX.”

“Overall, disease parameters were similar for GLM with the exception of BASDAI [Bath Ankylosing Spondylitis Disease Activity Index] where higher disease severity was observed among females” (P=0.007), they reported. For patients treated with IFX, between-gender differences were seen for CRP (C-reactive protein) with significantly lower levels in female patients (12.5mg/L vs. 19.2mg/L; P=0.012); however BASDAI  (P=0.013) and HAQ-DI [Health Assessment Questionnaire Disability Index] were significantly higher (P=0.019) in females compared to males.