The sensitivity to change of the ASAS Health Index in an observational real-life cohort study
Abstract
Objective The ASAS health index (ASAS-HI) measures global functioning and health in axSpA patients covering domains of physical, emotional and social functioning. Main aim was to investigate the sensitivity to change of ASAS-HI in comparison with established parameters of disease activity, function, and mental health.
Methods AxSpA patients from the disease register RABBIT-SpA with follow-up time of at least 12 months and available ASAS-HI questionnaires were included. Patients received questionnaires addressing disease activity (BASDAI, ASDAS), physical function (BASFI), mental health (WHO-5), and global functioning (ASAS-HI). Standardized response means (SRM) were calculated to compare the sensitivity to change of different parameters.
Results 667 patients were included, 552 treated with bDMARD and 115 with csDMARDs and/or NSAIDs. Between baseline and month 12, the mean ASAS-HI declined from 6.9 to 5.1 in the bDMARD group and from 5.9 to 5.6 in the conventionally treated group. In the bDMARD group, SRM of ASAS-HI was 0.52, compared to 0.59 for BASFI, 0.65 for WHO-5, 0.73 for BASDAI, and 0.9 for ASDAS. Following ASAS-HI domains were most frequently affected: pain (78% agreed), maintaining body position (75%), and energy/drive (73%). In the bDMARD patients, there was an improvement in all items. In the control group, the largest improvement was seen in pain.
Conclusion As expected, ASDAS and BASDAI as disease activity scores showed high sensitivity to change, while changes in physical function (BASFI), mental health (WHO-5), and the broader concept of functioning and health (ASAS-HI) were moderate.