Outcome of active disease in ankylosing spondylitis: a prospective study

People with ankylosing spondylitis (AS) typically experience episodic exacerbations, but the extent to which they subsequently experience a sustained reduction in disease markers below recognized thresholds for active disease is unclear.

To investigate changes in, and associations between, disease markers over 18 months in people with active AS.

Within a cohort of 89 participants with AS, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) scores of 4 or higher were used to identify those with active disease. Standard assessment tools were used to monitor participants prospectively at four consecutive six-monthly intervals. Participants received standard treatments but none received anti-tumor necrosis factor-alpha (TNFalpha) medication during the study.

The median age of the cohort was 50 years (inter-quartile range [IQR] 38.5-55.5), the median age of disease onset was 25 years (IQR 18-33) and the median disease duration was 18 years (IQR 13-27). Forty-seven (53%) participants had a BASDAI score of 4 or higher on the first assessment, of whom 45 (51%) scored 4 or higher on all subsequent assessments. Furthermore, 38 (43%) and 16 (18%) participants scored BASDAI 5 or 6, respectively, or higher, throughout. BASDAI scores correlated strongly with Bath Ankylosing Spondylitis Functional Index (BASFI) scores. Compared with 19 (21%) participants whose BASDAI scores were consistently below 4 throughout, participants with persistently high BASDAI scores showed higher scores for anxiety and depression, and some evidence of functional deterioration during the study period.

In this cohort, disease markers in most people with active AS were sustained above the standard threshold for active disease. This has important implications for planning care pathways and for optimal utilization of anti-TNFalpha treatment.