Definition of disease duration in ankylosing spondylitis: reassessing the concept.

The concept and definition of disease duration in patients with ankylosing spondylitis is ambiguous, and often many years pass between the onset of symptoms and diagnosis. Members of the Assessment in Ankylosing Spondylitis (ASAS) International Working Group by consensus recently recommended identifying specific components of the medical history to better define and document the concept of disease duration. These include (1) the time of onset of the first symptoms of axial manifestations (including inflammatory back pain); (2) the time of onset of the first symptoms of each individual manifestation, which may be an extra-axial sign or symptom of ankylosing spondylitis, such as peripheral arthritis and enthesitis; (3) the time of onset of associated diseases belonging to the spondyloarthritides, in particular acute anterior uveitis, inflammatory bowel disease and psoriasis; and (4) the time since actual diagnosis by a healthcare provider. Such uniformity in data collection will ensure comparability across studies and facilitate future research.