To compare the functional ability of patients with spondyloarthropathy (SpA) and fibromyalgia (FM) using the Bath Ankylosing Spondylitis Functional Index (BASFI), the Dougados Functional Index (DFI), and and the Health Assessment Questionnaire for Spondyloarthropathy (HAQ-S), to establish whether these indicators can differentiate between these patient groups, and to ascertain how well the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) functions in patients with FM.
Twenty-four patients with SpA and 70 with FM, all female, filled in 4 self-administered questionnaires: BASFI, DFI, HAQ-S, and the BASDAI; results were compared between the 2 groups.
The decline in functional ability was similar in patients with SpA and FM when assessed by BASFI, but slightly greater in the SpA group when assessed by DFI and HAQ-S. BASDAI was significantly (p = 0.018) greater in the FM group.
An almost similar functional decline was observed in both SpA and FM patients when measured by the indices developed for patients with AS and SpA. The specificity of BASDAI in measuring disease activity in SpA was poor, as disease activity in FM was rated higher than in SpA.