Joining a patient self-help organisation is recommended for patients with ankylosing spondylitis (AS). The objective was to compare AS patients who are members of a self-help organisation with non-members regarding disease specific and patient personality aspects, and make inferences on potential benefits of membership.

A comprehensive questionnaire regarding demographics, smoking habits, acquisition of information about the disease, disease activity, functioning, patient satisfaction, treatment, sick leave, work disability and educational level was distributed to members of the German AS self-help organisation and to non-member AS patients.

In total, 1273 patients responded. Significant differences regarding age and disease duration led us to match members 2:1 to non-members. In the matched population (n=549), members had a higher level of education, felt more often well-informed about the disease, had less often physically demanding jobs, and smoked less than non-members. Members were more often treated with NSAIDs and less often with TNF-blockers suggesting more severe disease in non-members. While the level of disease activity was similar (BASDAI 4.1 vs. 4.2), members had a better functional status (BASFI 3.5 vs. 3.9) and significantly less days on sick leave during the last year (15.1 days vs. 31.2 days). Days on sick leave increased with increasing BASFI significantly more strikingly in non-members than in members.

AS patients who are members of an AS self-help organisation have a higher educational level and are much better informed about the disease. Inferences on disease outcome measures, however, are hampered by potential confounders.