The presence of Fibromyalgia in Axial Spondyloarthritis can falsely accentuate disease activity, resulting in inappropriate therapeutic escalation. This is especially so if assessed by purely clinical measures like BASDAI. Moving to measures incorporating laboratory values of inflammation (eg ASDAS-CRP) should help to mitigate.
About 10% of Fibromyalgia patients were found to have Axial Spondyloarthritis by radiologic or clinical criteria. This is a sizable number, and the possibility of AS should be considered especially in those with elevated acute phase reactants.