Table 2

Performances of the cut-offs defining clinically important worsening

	Cut-off	Prospective real life study (n=1169 patients) against the external standard ’patient-worsening’ (worsening: n=127)		2015 case-vignette exercise* (n=1150 physician judgements) against the external standard ‘physician-worsening’ (worsening: n=591)
	Cut-off	Sensitivity	Specificity	Sensitivity	Specificity
Back pain (0–10)	Δ pain≥2 AND final pain≥4	0.42	0.91	0.99	0.30
	Δ pain≥3	0.29	0.95	0.95	0.69
	If back pain value is≥4, then Δ pain≥2 points, if else, Δ pain≥3 points	0.43	0.91	0.97	0.56
BASDAI (0–10)	Δ BASDAI≥2 points	0.31	0.96	0.99	0.40
	Δ BASDAI≥2 points AND final BASDAI≥4	0.24	0.98	0.99	0.32
	Δ BASDAI≥3 points	0.17	0.99	0.92	0.70
	Δ BASDAI≥3 points AND final BASDAI≥4	0.16	0.99	0.94	0.63
	If BASDAI value is≥4, then Δ BASDAI≥2 points, if else, Δ BASDAI≥3 points	0.25	0.98	0.94	0.54
ASDAS	ΔASDAS≥0.6	0.55	0.91	0.97	0.65
	ΔASDAS≥0.9	0.38	0.96	0.85	0.87
	ΔASDAS≥1.1	0.33	0.98	0.60	0.94
	Δ ASDAS≥0.6 AND final ASDAS≥1.3	0.55	0.91	0.97	0.59

*Gossec L, et al. Preliminary definitions of ’flare' in axial spondyloarthritis, based on pain, BASDAI and ASDAS-CRP: an ASAS initiative. Ann Rheum Dis. 2016;75:991–6.
ASAS, Assessment of SpondyloArthritis International Society; ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Activity Index; CRP, C reactive protein.