Ho Index for Predicting Response to Medical Therapy in IBD
Clinical index predicting long-term steroid-free remission in patients with IBD treated with azathioprine or 6-mercaptopurine. Helps identify patients unlikely to respond to thiopurines who may benefit from early biologic therapy.
Score interpretation
Low Ho Index -- reasonable probability of thiopurine response (~60-75% 1-year steroid-free remission)
→ Start azathioprine 2-2.5 mg/kg/day (CD/UC) or 6-mercaptopurine 1-1.5 mg/kg/day; check TPMT genotype/activity before starting (homozygous low TPMT: very high myelosuppression risk -- consider 6-TGN monitoring or dose reduction); FBC at weeks 2, 4, 8, then 3-monthly; monitor LFTs; warn patient: 3-6 months to full effect; lymphoma risk (absolute risk ~1.5x background, rare); TPMT-guided dosing reduces toxicity; co-prescribe allopurinol 100 mg OD if thiopurine metabolite optimisation needed (AZTG monitoring); avoid live vaccines.
Moderate Ho Index -- intermediate thiopurine response (~40%) -- evaluate for early biologic therapy
→ Discuss with patient: 40% chance of achieving remission on thiopurine alone; alternative: anti-TNF therapy (infliximab 5 mg/kg IV at 0, 2, 6 weeks then 8-weekly; adalimumab 160/80/40 mg SC induction then 40 mg fortnightly); combination therapy (anti-TNF + thiopurine) more effective than monotherapy -- SONIC trial CD; SELECT UC trial for UC; monitor drug levels (infliximab trough >= 3-7 mg/L; adalimumab trough >= 5-7 mg/L); IBD nurse specialist; faecal calprotectin monitoring; target treat-to-target (T2T) strategy -- mucosal healing as endpoint.
High Ho Index -- ~20% thiopurine response; early biologic therapy strongly recommended
→ Proceed directly to biologic therapy (do not delay with thiopurine trial): anti-TNF (infliximab or adalimumab) first-line for CD and UC; if prior anti-TNF failure: vedolizumab (gut-selective, CD and UC) or ustekinumab (CD, now UC approved); tofacitinib (JAK inhibitor, UC); ozanimod/filgotinib (JAK inhibitor, UC); multidisciplinary IBD team meeting; surgery discussion if appropriate (ileostomy, colectomy for refractory UC); nutritional support: exclusive enteral nutrition for active CD as alternative to steroids (ECCO guideline); colorectal surgery referral for bowel preparation; clinical trial enrolment; ECCO IBD guidelines for escalation pathway.
Interpretation bands for the Ho Index IBD. Apply clinical judgement and local guidance.
References
- Ho GT et al. The use of immunosuppressive therapy in inflammatory bowel disease: survey of adherence to published guidelines. Aliment Pharmacol Ther. 2006;23(7):1009-1018.
- NICE NG129. Crohn's disease: management. NICE. 2019 (updated 2022).
Related
Curated clinical cross-links plus same-class fallbacks.
- Harvey-Bradshaw Index for Crohn's Disease · Inflammatory Bowel Disease
- Mayo Score for Ulcerative Colitis Activity · Inflammatory Bowel Disease
- Crohn's Disease Activity Index (CDAI) · Inflammatory Bowel Disease
- Truelove and Witts Severity Index for Ulcerative Colitis · Inflammatory Bowel Disease
- Ulcerative Colitis Endoscopic Index of Severity (UCEIS) · Inflammatory Bowel Disease
- Simplified Endoscopic Score for Crohn's Disease (SES-CD) · Inflammatory Bowel Disease
- Natalizumab · Disease-Modifying Therapy — MS (Anti-VLA-4 Monoclonal Antibody)
- Dapsone · Anti-inflammatory / Antimicrobial
- Colchicine · Anti-inflammatory — Neutrophilic Dermatoses / Vasculitis
- Diclofenac · Non-Steroidal Anti-Inflammatory Drug (NSAID)
- Colchicine (Acute Gout) · Anti-Inflammatory (Microtubule Inhibitor)
- Diclofenac · NSAID (Non-Steroidal Anti-Inflammatory Drug)
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.