Table 2

Sensitivity and specificity of ASDAS cut-off values for disease activity states and levels of improvement against several external criteria in NOR-DMARD and ASSERT

		NOR-DMARD (ASDAS-CRP)			NOR-DMARD (ASDAS-ESR)			ASSERT (ASDAS-CRP)
ASDAS cut-offs and external criterion	Timepoint	SE	SP	n	SE	SP	n	SE	SP	n
ASDAS <1.3:
ASAS partial remission	3 Months	66.7	88.8	310	78.3	86.3	310	80.6	92.3	219
ASAS partial remission	6 Months	60.0	91.2	192	82.2	91.2	192	87.2	90.0	219
Patient global <1	3 Months	69.9	90.7	310	71.2	85.2	310	82.1	89.6	220
Patient global <1	6 Months	67.5	85.6	207	80.0	82.6	207	81.3	86.1	219
Physician global <1	3 Months	44.4	88.3	305	56.5	87.8	305	–	–	–
Physician global <1	6 Months	71.9	85.6	199	84.4	82.6	199	–	–	–
ASDAS <2.1:
Patient global <3	3 Months	80.4	87.3	310	91.7	80.3	310	81.7	90.6	220
Patient global <3	6 Months	83.6	89.7	207	93.6	85.6	207	87.2	83.5	220
Physician global <3	3 Months	59.3	88.7	305	70.0	83.9	305	–	–	–
Physician global <3	6 Months	84.3	89.7	199	94.1	85.6	199	–	–	–
ASDAS >3.5:
Patient global >6	Baseline	74.8	79.2	442	59.4	88.3	442	85.2	58.0	223
Physician global >6	Baseline	79.2	59.4	432	67.9	71.5	432	–	–	–
ΔASDAS ≥1.1:
Better or much better	3 Months	62.7	86.7	252	63.8	80.0	252	–	–	–
Better or much better	6 Months	61.7	96.8	164	60.2	90.3	164	–	–	–
ASAS20	3 Months	84.5	83.8	258	86.2	80.3	258	83.6	87.0	220
ASAS20	6 Months	83.3	79.3	165	85.9	81.6	165	84.1	90.3	219
ΔASDAS ≥2.0:
Much better	3 Months	56.4	90.2	252	59.0	93.7	252	–	–	–
Much better	6 Months	53.8	90.2	164	50.0	91.1	164	–	–	–
ASAS40	3 Months	64.9	93.9	258	61.0	94.5	258	86.5	80.8	220
ASAS40	6 Months	60.4	93.8	165	54.7	93.8	165	83.7	90.2	219

ASAS20 and ASAS40 response criteria are based on four independent domains: spinal pain, physical function measured by the BASFI, patient global assessment and inflammation measured as the mean of the last two BASDAI questions (severity and duration of morning stiffness); ASAS20 treatment response is defined as improvement of ≥20% and ≥1 unit (range 0–10) in at least three of the four above domains, and no worsening of ≥20% and ≥1 unit in the remaining fourth domain; ASAS40 treatment response is defined as improvement of ≥40% and ≥2 units in at least three of the four above domains, and no worsening in the remaining fourth domain; ASAS partial remission criteria are fulfilled if the value for all four domains is below 2. Range of patient and physician global assessment is 0–10.
ASAS, Assessment of SpondyloArthritis international Society; ASDAS, Ankylosing Spondylitis Disease Activity Score; ASSERT, Ankylosing Spondylitis Study for the Evaluation of Recombinant Infliximab Therapy; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; CRP, C reactive protein; ESR, erythrocyte sedimentation rate; NOR-DMARD, Norwegian register of disease modifying antirheumatic drugs.