Free tool
BASDAI calculator
The Bath Ankylosing Spondylitis Disease Activity Index is a six-question, self-completed measure of how active ankylosing spondylitis or axial spondyloarthritis has felt over the past week. Answer the six questions below to see your score and how it was worked out. Nothing is saved and no account is needed.
Published
Reading the number
The score runs from 0 to 10. Higher means the condition has felt more active over the past week.
In UK guidance, TNF-alpha inhibitors are an option for active ankylosing spondylitis or non-radiographic axSpA when the BASDAI is 4 or more and a spinal pain score is 4 cm or more on a visual analogue scale, and NSAIDs have not controlled the condition well enough or are not tolerated (NICE TA383). That is a decision rule for clinicians within a specific guideline, not a line between fine and not fine.
A single score is a snapshot. The trend over months, alongside the daily symptoms underneath it, is what a rheumatology team can use.
What BASDAI is
The BASDAI was developed at the Royal National Hospital for Rheumatic Diseases in Bath and published in 1994 (Garrett et al.). It was designed with input from people with AS and covers five symptoms: fatigue, spinal pain, pain or swelling in other joints, tenderness where tendons and ligaments attach, and morning stiffness — the last of these with two questions, for severity and duration.
It is commonly used to assess disease activity in ankylosing spondylitis and across the axial spondyloarthritis spectrum, in clinics and in research. It takes most people under two minutes.
How the calculation works
Questions 1 to 4 are added together (A). Questions 5 and 6 both concern morning stiffness, so they are averaged (B) to stop stiffness counting twice. A and B are added and divided by 5 to give a score from 0 to 10.
The sixth question is a duration. On the standard form the scale runs from none, through 1 hour at the midpoint, to 2 or more hours at 10; the slider here is labelled the same way.
BASDAI = ( (Q1 + Q2 + Q3 + Q4) + (Q5 + Q6) ÷ 2 ) ÷ 5
What the score is not
It is not a diagnosis. The BASDAI is used by people who already have a diagnosis of ankylosing spondylitis or axial spondyloarthritis. A high score in someone without one means nothing by itself.
It is self-reported, and describes how the past week felt. It does not measure inflammation directly or structural change; those need blood tests and imaging.
It should not be used to start, stop or change any treatment on your own. Take the score — and the trend — to your rheumatology team.
Medical disclaimer
This calculator is an educational tool. It is not medical advice, not a diagnostic test and not a medical device. HAVYT does not diagnose ankylosing spondylitis or any other condition. If you have symptoms that concern you, speak to a clinician; for eye pain or redness, chest pain, numbness or weakness, seek urgent care.
Sources
- Garrett S, Jenkinson T, Kennedy LG, Whitelock H, Gaisford P, Calin A. A new approach to defining disease status in ankylosing spondylitis: the Bath Ankylosing Spondylitis Disease Activity Index. J Rheumatol 1994;21(12):2286–91
- The Bath Indices: outcome measures for use with ankylosing spondylitis patients (BASMI, BASFI, BASDAI, BAS-G)
- TA383 — TNF-alpha inhibitors for treating active ankylosing spondylitis and non-radiographic axial spondyloarthritis
- NG65 — Spondyloarthritis in over 16s: diagnosis and management
- Ankylosing spondylitis: overview