BASDAI Calculator
Bath Ankylosing Spondylitis Disease Activity Index - Assess disease activity in axial spondyloarthritis
Patient Assessment
Rate each question on a scale of 0 (none) to 10 (very severe) based on the average over the past week:
How would you describe the overall level of fatigue/tiredness you have experienced?
How would you describe the overall level of AS neck, back or hip pain you have had?
How would you describe the overall level of pain/swelling in joints other than neck, back, or hips?
How would you describe the overall level of discomfort you have had from any areas tender to touch or pressure?
How would you describe the overall level of morning stiffness you have had from the time you wake up?
How long does your morning stiffness last from the time you wake up?
Results
Interpretation
Clinical Significance
- • BASDAI ≥ 4 = threshold for biologics
- • Change ≥ 2 points = meaningful improvement
- • 50% improvement = BASDAI50 response
- • Assess monthly during active treatment
Formula
BASDAI = (Q1 + Q2 + Q3 + Q4 + (Q5+Q6)/2) / 5
Morning stiffness (Q5+Q6) is averaged before inclusion
💡 Clinical Tip
Use BASDAI with patient global assessment and CRP/ESR for comprehensive disease monitoring. Consider imaging (MRI, X-ray) for structural progression assessment.
Understanding BASDAI Score
The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) is a validated, patient-reported outcome measure used to assess disease activity in patients with ankylosing spondylitis (AS) and other forms of axial spondyloarthritis. It was developed at the Royal National Hospital for Rheumatic Diseases in Bath, UK.
Components of BASDAI
BASDAI consists of 6 questions using a Visual Analog Scale (VAS) from 0 to 10:
- Fatigue: Overall level of fatigue/tiredness
- Spinal pain: Neck, back, or hip pain
- Peripheral joint pain/swelling: Joints other than spine/hips
- Enthesitis: Areas tender to touch or pressure
- Morning stiffness severity: Intensity upon waking
- Morning stiffness duration: How long it lasts (0=none, 10=2+ hours)
Clinical Application
BASDAI guides treatment decisions in axial spondyloarthritis:
- Treatment Initiation: BASDAI ≥ 4 is a key criterion for starting biologic therapy (TNF inhibitors, IL-17 inhibitors)
- Response Assessment: A 50% reduction (BASDAI50) or 2-point absolute reduction indicates good response
- Treatment Targets: Aim for BASDAI < 4 to indicate inactive disease
- Monitoring Frequency: Assess monthly when adjusting therapy, every 3-6 months when stable
Interpretation Guidelines
The BASDAI score ranges from 0 to 10:
- < 4: Inactive or well-controlled disease - continue current therapy
- ≥ 4: Active disease - consider treatment intensification, especially biologics if NSAIDs insufficient
- Change ≥ 2 points: Clinically meaningful improvement or worsening
- ≥ 50% reduction: Excellent response (BASDAI50 - common endpoint in trials)
ASAS Biologic Therapy Criteria
According to ASAS (Assessment of SpondyloArthritis international Society), biologics are indicated when:
- BASDAI ≥ 4 (on 0-10 scale)
- Expert opinion (patient has active disease)
- Inadequate response to at least 2 NSAIDs over 4 weeks at maximum recommended dose
- Either spinal pain ≥ 4 or patient global ≥ 4 (on 0-10 scale)
BASDAI Components and Scoring
| Question | Domain | What It Measures | Scoring |
|---|---|---|---|
| Q1 | Fatigue | Overall fatigue/tiredness level | 0-10 VAS |
| Q2 | Axial pain | Neck, back, or hip pain | 0-10 VAS |
| Q3 | Peripheral joints | Joint pain/swelling (other than spine/hips) | 0-10 VAS |
| Q4 | Enthesitis | Tenderness to touch/pressure | 0-10 VAS |
| Q5 | Morning stiffness | Severity of morning stiffness | 0-10 VAS (averaged with Q6) |
| Q6 | Morning stiffness | Duration of morning stiffness | 0-10 VAS (averaged with Q5) |
Note: Q5 and Q6 are averaged together before the final calculation, giving morning stiffness equal weight to other domains.
Frequently Asked Questions
What time period should patients consider when answering BASDAI questions?
Patients should base their answers on the average of the past week (last 7 days). This timeframe provides a representative assessment of recent disease activity while minimizing day-to-day variability.
Why is BASDAI ≥ 4 the threshold for biologic therapy?
The threshold of 4 was established through clinical trials and represents the level of disease activity that significantly impacts quality of life and warrants more aggressive treatment. This cutoff balances the need for effective treatment against the risks and costs of biologic therapy, and has been validated in multiple studies showing improved outcomes when biologics are initiated at this level.
How does BASDAI differ from ASDAS?
BASDAI is purely patient-reported, while ASDAS (Ankylosing Spondylitis Disease Activity Score) combines patient-reported measures with an objective inflammatory marker (CRP or ESR). ASDAS may be more sensitive to change and better correlates with inflammation on MRI. Both are valid; many clinicians use BASDAI for its simplicity and ASDAS when objective confirmation of inflammation is needed.
Can BASDAI be used for non-radiographic axial spondyloarthritis?
Yes, BASDAI can be used for both ankylosing spondylitis (radiographic axial SpA) and non-radiographic axial spondyloarthritis (nr-axSpA). The assessment and treatment thresholds are the same for both conditions, as they represent a spectrum of the same disease process.
What constitutes a good response to treatment based on BASDAI?
A good response is typically defined as: (1) BASDAI50 - a 50% reduction from baseline, or (2) an absolute reduction of ≥ 2 points on the 0-10 scale. For example, a drop from 6.0 to 3.0 represents both a 50% reduction and a 3-point absolute reduction, indicating excellent response. Achieving BASDAI < 4 is the treatment target.
Are there other assessment tools used with BASDAI?
Yes, comprehensive assessment often includes: BASFI (Bath AS Functional Index) for function, BASMI (Bath AS Metrology Index) for spinal mobility, patient global assessment, physician global assessment, and inflammatory markers (CRP/ESR). The ASAS response criteria combine several measures to define improvement. Using multiple tools provides a more complete picture of disease status and treatment response.
How often should BASDAI be assessed?
Assessment frequency depends on disease activity and treatment changes. During active treatment adjustment (e.g., starting or switching biologics), monthly assessment is recommended. Once disease is stable and treatment is optimized, assessment every 3-6 months is typically sufficient. More frequent monitoring helps detect flares early and allows timely treatment adjustments.
What are the limitations of BASDAI?
BASDAI is subjective and patient-reported, so it may be influenced by factors like mood, fibromyalgia, or other comorbidities. It doesn't include objective measures of inflammation or structural progression. Morning stiffness duration (Q6) may be difficult to quantify precisely. Despite these limitations, BASDAI remains highly validated and widely used because it captures the patient's experience of disease impact, which is ultimately what treatment aims to improve.