Is ASDAS better than BASDAI as a measure of disease activity in axial psoriatic arthritis?
OBJECTIVE
To assess the discriminative ability and correlation of the Ankylosing Spondylitis Disease Activity Score (ASDAS) and Bath Ankylosing Spondylitis Activity Disease Activity Index (BASDAI) with disease activity in axial psoriatic arthritis (AxPsA).


METHODS
Patients with AxPsA were selected from a large prospective cohort study of psoriatic arthritis. Patient and physician global scores were used as constructs of disease activity. Patients were categorised into high and low disease activity states based on patient and physician global assessment scores and physician's decision to change treatment. Statistical analysis included descriptive statistics, linear and logistic regression.


RESULTS
201 patients with AxPsA were included in the study. ASDAS and BASDAI showed good correlation with disease activity as reflected by the patient global score (correlation coefficients (r) for BASDAI 0.84, ASDAS-B 0.77, ASDAS-C 0.81, p < 0.001) and the physician global score (r = 0.53 for BASDAI, r = 0.50 for ASDAS-B, r = 0.55 for ASDAS-C, p < 0.001). Both scores showed good discriminative ability between high and low disease activity states. However, there were no significant differences between areas under the curve for the models that compared ASDAS with BASDAI for each definition of disease activity state.


CONCLUSIONS
In patients with AxPsA, ASDAS and BASDAI scores show similar good to moderate discriminative ability and correlation with different constructs of disease activity. ASDAS was not superior to BASDAI in its ability to discriminate between high and low disease activity states in AxPsA.
Eder
Lihi
L
Centre for Prognosis Studies in the Rheumatic Diseases, University of Toronto Psoriatic Arthritis Clinic, Toronto Western Hospital, Toronto, Ontario, Canada.
Chandran
Vinod
V
Shen
Hua
H
Cook
Richard J
RJ
Gladman
Dafna D
DD
D000328:Adult; D000368:Aged; D015535:Arthritis, Psoriatic / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy; D001416:Back Pain / Q000209:etiology; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058566:Sacroiliitis / Q000175:diagnosis / Q000209:etiology; D012720:Severity of Illness Index