The Harvey-Bradshaw Index is the sum of general well-being, abdominal pain, liquid stools, abdominal mass, and complications.
Enter an HBI score to visualize the estimated CDAI equivalence and disease severity stratification.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Comparing disease activity severity between patients scored with HBI vs. CDAI
Applying clinical trial "inclusion criteria" (usually CDAI 220–450) to routine clinic patients (usually scored with HBI)
Standardizing results for academic publications and case conferences
The 'Snapshot' Accuracy
Because CDAI averages symptoms over 7 days and HBI is taken "Today," the conversion is most accurate when the patient's symptoms have been stable for at least one week.
Section 2
Formula & Logic
Linear Regression model
The most widely accepted conversion utilizes a linear regression model derived from a database of 2,166 observations where both scores were calculated simultaneously.
Formula (Best 2006)
Predicted CDAI = (HBI × 13.0) + 40
Severity Equivalence
Remission
HBI < 5 ≈ CDAI < 150
Mild
HBI 5–7 ≈ CDAI 150–220
Moderate
HBI 8–16 ≈ CDAI 221–450
Severe
HBI > 16 ≈ CDAI > 450
Section 3
Pearls/Pitfalls
Missing Components
Users must be aware that the CDAI includes Haematocrit and Weight, whereas the HBI does not. In a patient with significant weight loss but few GI symptoms, the HBI will "under-predict" the CDAI severity.
Clinical Pearls
HBI of 8 is the classical "cutoff" for moderate activity in most clinical trials
A change of 1 HBI point is equivalent to ~15 CDAI points
A 3-point HBI drop (~100 CDAI points) is a universal marker of clinical response
Section 4
Next Steps
Trial Eligibility
01
HBI 8–16: Indicates Moderate disease. Likely eligible for most biological induction clinical trials.
02
HBI < 5: Indicates Remission. Target outcome for any successful Crohn's therapy.
Complementary Tools
Harvey-Bradshaw Index (HBI)
Crohn's Disease Activity Index (CDAI)
SES-CD (Endoscopic Score)
Section 5
Evidence Appraisal
Statistical Foundation
Predicting the Crohn's disease activity index from the Harvey-Bradshaw index.
Best WR. • Clin Gastroenterol Hepatol.. 2006;4(3):304-10. Establishing the canonical conversion factors.
