BASDAI

A validated six-item 0–10 patient-reported index summarizing five ankylosing-spondylitis symptom domains through a specified stiffness-weighted scoring rule.

Version

v1 · 2026-09-28 · History

Domain-specific #

8121

Domain group

Applied Sciences & Engineering

Origin domain

Medicine & Healthcare

Subdomains

Rheumatology, Patient Reported Outcomes → Medicine & Healthcare

Core Idea

BASDAI captures recent symptom burden directly from the patient: fatigue, spinal pain, peripheral joint pain or swelling, enthesitis, and the severity and duration of morning stiffness. All six items use the same 0–10 response range.

Scoring first averages the two stiffness items, then averages that result with the other four domains to yield 0–10. The index can monitor disease activity and response, but diagnosis and treatment require broader clinical evidence.

How would you explain it like I'm…

The Six-Question Ache Score

A doctor asks a person with an achy, stiff-back illness six questions, and each answer is a number from 0 to 10, like how tired they feel and how much their back hurts. The numbers are mixed together into one score from 0 to 10 that shows how much the illness has been bothering them lately. It helps check whether treatment is working, but it can't tell by itself what illness someone has.

Symptom Score From 0 to 10

BASDAI is a short questionnaire that a patient fills out about how their illness has been affecting them recently. It asks about six things, each rated from 0 to 10: tiredness, back or spine pain, pain or swelling in other joints, sore spots where tendons attach to bone, how bad morning stiffness is, and how long it lasts. The two morning-stiffness answers are averaged first, and then that is averaged with the other four to make one score between 0 and 10. Doctors use it to see how active the illness is and whether treatment is helping. It isn't used by itself to decide what illness a person has or which treatment to choose.

Patient-Reported Disease Activity Index

BASDAI is a patient-reported index of recent symptom burden. It has six items, all answered on the same 0–10 scale: fatigue, spinal pain, peripheral joint pain or swelling, enthesitis (tenderness where tendons and ligaments attach to bone), severity of morning stiffness, and duration of morning stiffness. To score it, the two morning-stiffness items are averaged first, and that average is then averaged with the other four items, giving a final score from 0 to 10. Because the stiffness items are combined first, stiffness counts as one domain out of five rather than two out of six. It is used to monitor disease activity and response to treatment, but diagnosis and treatment decisions require broader clinical evidence.

 

BASDAI is a self-reported disease-activity index that captures recent symptom burden directly from the patient across six items, all scored on a common 0-10 range: fatigue, spinal pain, peripheral joint pain or swelling, enthesitis, severity of morning stiffness, and duration of morning stiffness. Scoring averages the two stiffness items into a single stiffness domain and then averages that with the four other domains, so the final score is (item1 + item2 + item3 + item4 + mean(item5, item6)) / 5, again on 0-10. Because it is a composite of subjective ratings, it measures how the patient experiences the disease rather than objective inflammation or structural change. It is used to monitor disease activity and response to therapy over time. It is not a diagnostic test, and treatment decisions require broader clinical evidence.

Scope of Application

• Rheumatology visits. Tracks patient-reported activity over time.
• Treatment evaluation. Adds symptom response to broader assessment.
• Clinical trials. Provides a standardized outcome measure.
• Service audit. Summarizes cohorts with population caveats.
• Research. Studies relationships among symptoms and other disease measures.

Clarity

Report language/version, population, recall period, administration mode, all six item scores, missing-data handling, calculation, final 0–10 value, date, treatment context, and complementary measures. Preserve patient-reported provenance. Inclusion test: Require the validated six-item self-report administered and scored with the stiffness average and five-domain mean, while interpreting the final value as one disease-activity measure in the appropriate population. Exclusion test: Exclude using BASDAI to diagnose ankylosing spondylitis, modifying item wording or recall without validation, summing six items without weighting, and treating a threshold as an automatic treatment command. Nearest boundary: ASDAS combines patient reports with additional variables and a distinct scoring model; BASDAI is the simpler six-item symptom index. Exit condition: The identity fails when item set, response scale, or prescribed aggregation is materially changed. Common misclassifications: It is not a diagnostic test by itself. It is not a six-item unweighted sum. It is not an objective inflammation biomarker. It is not an automatic prescription at one cutoff. Nearest named distinctions: Diagnostic Criteria: Establish disease classification using broader evidence rather than current symptom severity alone. ASDAS: A distinct composite with another variable set and algorithm. BASFI: Assesses function rather than disease activity symptoms. Pain Scale: One symptom rating rather than the validated multidomain calculation.

Manages Complexity

The index compresses multiple symptom dimensions into a repeatable score while retaining equal domain weighting. Its convenience enables longitudinal comparison but hides item patterns unless the six responses remain available.

Abstract Reasoning

1. Confirm the validated version and intended population.
2. Collect all six patient ratings under consistent instructions.
3. Check range and missing responses.
4. Average stiffness severity and duration.
5. Average the resulting five domains.
6. Interpret level and change alongside clinical and objective evidence.

Knowledge Transfer

The transferable cargo is a transparent composite patient-reported activity index. It transfers methodologically to other instruments, but BASDAI items, weights, thresholds, and disease meaning do not.

Neighborhood in Abstraction Space

BASDAI sits in a moderately populated region (59^th percentile for distinctiveness): it has near-neighbors but no dense thicket of look-alikes.

Family — Applied Assessment Frameworks & Practices (26 abstractions)

Nearest neighbors

• Modified Ashworth scale — 0.86
• Electroneuronography — 0.86
• Clinical Grading System — 0.85
• Disease Burden — 0.84
• Posturography — 0.84

Computed from structural-signature embeddings · 2026-10-08