Disease activity in ankylosing spondylitis. Free to use.
BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) is a validated clinical instrument used to assess disease activity in ankylosing spondylitis. The instrument contains 6 items.
Source / attribution: Garrett S et al. J Rheumatol. 1994;21(12):2286-2291.
The instrument's primary construct — disease activity in ankylosing spondylitis — is operationalized through a fixed set of items, each with a defined response format. This standardisation is what allows BASDAI scores to be compared meaningfully across clinicians, sites, and studies.
Like all screening or assessment instruments, BASDAI is a structured aid — not a diagnostic test in isolation. Results should be interpreted alongside history, examination, and clinical context. Where a score crosses an actionable threshold, the next step is typically a more detailed clinical evaluation rather than a definitive diagnosis.
Answer all 6 items below to see your BASDAI score and interpretation.
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BASDAI uses a published formula (basdai) rather than simple summation. The formula and its inputs are visible in our open-source scoring engine.
Scoring notes: BASDAI = (q1 + q2 + q3 + q4 + (q5 + q6) / 2) / 5; range 0–10.
The cutoffs below are drawn from the published validation literature. Always interpret in clinical context.
| Score range | Band | Interpretation |
|---|---|---|
| 0–3.9 | Inactive disease | Disease activity below the conventional 4.0 cutoff. |
| 4–10 | Active disease | ≥ 4.0 indicates active disease; consider treatment intensification. |
BASDAI uses a published formula rather than simple summation. Below is a step-by-step calculation with illustrative inputs.
| Input | Value |
|---|---|
| Q1–Q4 | each = 5 |
| Q5 | 5 |
| Q6 | 5 |
Score = 5 → Active disease
If BASDAI doesn't fit your context, related instruments in rheumatology include:
| Scale | Measures | Items | Time |
|---|---|---|---|
| BASFI | Functional limitation in ankylosing spondylitis | 10 | — |
| ODI | Self-reported low-back-pain functional disability | 10 | — |
| NDI | Self-reported neck-pain functional disability | 10 | — |
| Oxford Knee Score | Pain and function after total knee replacement | 12 | — |
| Oxford Hip Score | Pain and function after total hip replacement | 12 | — |
| LEFS | Function with lower-extremity musculoskeletal disorders | 20 | — |
| IPSS | Lower-urinary-tract symptoms in men | 7 | — |
| IIEF-5 / SHIM | Erectile dysfunction screen | 5 | — |
BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) is a validated instrument that assesses disease activity in ankylosing spondylitis. It is designed for clinicians, medical students, evidence-synthesis researchers. The 6 items are combined to produce a total score.
BASDAI contains 6 items. Items feed into a scoring formula that produces the total. Scores run from 0 to 10, grouped into 2 interpretation bands from ‘Inactive disease’ up to ‘Active disease’.
On the BASDAI (total score 0–10), scores of 4–10 fall in the ‘Active disease’ band — interpreted as: ≥ 4.0 indicates active disease; consider treatment intensification. The full ladder is: 0–3.9 — Inactive disease: Disease activity below the conventional 4.0 cutoff.; 4–10 — Active disease: ≥ 4.0 indicates active disease; consider treatment intensification. A higher score reflects a more severe presentation, and crossing a cutoff is a prompt to step up assessment or care — but these bands are screening thresholds, not diagnoses.
Scores of 0–3.9 fall in the ‘Inactive disease’ band: Disease activity below the conventional 4.0 cutoff. A low score is reassuring but does not by itself rule out the underlying condition — if symptoms or clinical suspicion persist, reassess over time or use a complementary evaluation rather than relying on the number alone.
Yes — BASDAI is in the public domain and free for clinical, educational, and research use without permission. You can use this calculator and the scale itself freely; if you publish results or reproduce the scale, cite the original source paper.
Garrett S et al. A new approach to defining disease status in ankylosing spondylitis. J Rheumatol. 1994;21(12):2286-2291. This is the original publication for the BASDAI — the reference to cite when reporting results.
No. BASDAI is a structured assessment aid, not a diagnostic test. Its proper role is clinical assessment of disease activity in ankylosing spondylitis — it standardizes assessment and flags who needs closer evaluation, but the result must be weighed alongside history, examination, and clinical context. When a score conflicts with your clinical impression, clinical judgment takes precedence; treatment decisions should never rest on a screening score alone.
BASDAI is supported by the following peer-reviewed sources: