125- Localized tenderness/enthesopathy
- Morning stiffness (2 questions)
The answers to these questions are scored on a 0–10 NRS, which is anchored by
0 ( none ) to 10 ( very severe ). The BASDAI sum score is calculated by the sum of
questions 1–4 plus the mean of questions 5 and 6, then the total is divided by 5.
The sum score ranges from 0 to 10; higher values indicate more active disease.
A BASDAI score ≥ 4/10 is considered as the threshold above which a disease status
can be considered as “active” [ 17 ]. However, this value has been proposed arbi-
trarily and its validity has not been formally established [ 18 ]. Nevertheless, a
BASDAI value of 3.9/10 discriminated between patients with well-controlled and
poorly controlled symptoms in AS [ 19 ].
A change of at least 50 % in the BASDAI is usually considered as refl ecting a clini-
cally relevant improvement [ 17 ]. The minimum clinically important difference (MCID)
between measurements has been reported as a change in BASDAI of ≥1/10 units on
NRS or ≥10 mm on VAS or a score difference of 22.5 % between two different exami-
nations of the same patient, with a sensitivity of 0.65 and a specifi city of 0.82 [ 20 ].
However, BASDAI scores do not seem to not correlate well with symptoms and
clinical measurements of disease activity and/or MRI scores [ 21 – 23 ]. Furthermore,
the degree of spinal infl ammation seems to be largely similar in patients with AS
and nr-axSpA, irrespective of the corresponding BASDAI level, which challenges
the concept of the (initially arbitrarily) chosen cutoff of BASDAI ≥ 4 for defi nition
of high disease activity [ 24 ].
The BASDAI is the most frequently used measure of disease activity in daily care
and in clinical trials. In most countries a BASDAI ≥ 4 is mandatory before prescrip-
tion of tumor-necrosis-factor inhibitors (TNFi). Because of the limitation of this
threshold, expert opinion is mandatory in order to prescribe TNFi. There is some
evidence that patients with AS may respond to TNF inhibitors despite not fulfi lling
the ASAS criteria for initiating TNFi therapy [ 25 ], but this, however, represents an
off-label use.
Ankylosing Spondylitis Disease Activity Score
Since the BASDAI is a purely patient- based questionnaire without any objective
parameters of disease activity, a new measure, the AS Disease Activity Score
(ASDAS) recently has been proposed [ 26 ]. This composite index takes into account
some questions of the BASDAI (Q2: total back pain, Q3: peripheral pain, and Q6:
morning stiffness), patient’s global assessment and C-reactive protein (CRP) or
erythrocyte sedimentation rate (ESR) values. The statistical background of the
ASDAS to ensure that each item of ASDAS adds extra information not yet captured
by the other items, and, thus, is not redundant. Response to the items and value of
serological markers are weighted and calculated to give the fi nal ASDAS score.
The score is most easily calculated using a calculator (online via http://www.asas-group.org ).
Scores range from 0 (no disease activity) to infi nite (being determined by the level
5 PROMs for Spondyloarthritis