About the Ho Index for Acute Severe Ulcerative Colitis
Three items scored on day 3 of intravenous corticosteroids, totalling 0 to 9. Mean daily stool frequency over the first three days contributes 0, 1, 2 or 4 points; colonic dilatation greater than 5.5 cm contributes 4; and an admission albumin below 30 g/L contributes 1. A total of 0–1 carried roughly an 11% risk of colectomy, 2–3 about 45%, and 4 or more about 85%, with the threshold of 4 giving approximately 85% sensitivity and 75% specificity for failure of intravenous steroids. The single most important structural fact is that colonic dilatation alone scores 4 and therefore reaches the high-risk band on its own.
Formula
Scored on day 3 of intravenous corticosteroids.
Mean daily stool frequency over the first 3 days
under 4 -> 0
4 to under 6 -> 1
6 to under 9 -> 2
9 or more -> 4
Colonic dilatation > 5.5 cm -> 4
Albumin < 30 g/L on admission -> 1
Total 0-9
0-1 -> approximately 11% progress to colectomy
2-3 -> approximately 45%
>= 4 -> approximately 85% (sensitivity ~85%, specificity ~75%
for intravenous steroid failure)- Colonic dilatation — 4 points
- The heaviest single item, equal to the maximum stool-frequency band. It reaches the high-risk threshold on its own, which is the score's sharpest clinical statement.
- The stool-frequency bands
- Note the jump from 2 to 4 points at nine stools — there is no 3-point band. The scale is deliberately non-linear at the top.
- Albumin — 1 point
- The admission value. Light in the scoring but the only nutritional variable present, and it rarely changes the band on its own.
- Derived in 167 consecutive patients with severe ulcerative colitis in Edinburgh between 1995 and 2002.
- The published bands overlap at 6 and 9 stools; this implementation reads them as half-open intervals, which is the only partition consistent with a maximum of 9.
- The stool figure is a three-day mean, unlike the Travis criteria which use the day 3 count.
- Albumin is the admission value, not the day 3 value.
Interpreting the result
A score of 4 or more should prompt active planning for rescue therapy or surgery on that day, with the colorectal team involved rather than notified. Look at what is driving the score before acting on the number: a 4 composed entirely of colonic dilatation is a different clinical situation from a 4 built from stool frequency alone, and the former carries an urgency the total does not convey — toxic megacolon needs recognising as such, independent of any score. The intermediate band, 2 to 3, is where the index is least decisive and where daily clinical reassessment matters most; it is also where cross-checking against the Travis criteria is most worthwhile, since Travis uses CRP and may flag a patient this score does not. A low score should not be read as reassurance about the admission — continue intravenous steroids with daily review and reassess at day 7, where the Travis study's second finding still applies. In every band, exclude Clostridioides difficile and cytomegalovirus superinfection before attributing non-response to refractory colitis, and confirm that thromboprophylaxis is prescribed, which is the most commonly omitted intervention on these admissions.
| Score | Band | What it means | Action |
|---|---|---|---|
| 0–1 | Low risk | Approximately 11% progress to colectomy | Continue intravenous corticosteroids with daily review; reassess at day 7 regardless |
| 2–3 | Intermediate risk | Approximately 45% progress to colectomy | The least decisive band — reassess daily, cross-check against the Travis criteria |
| 4 or more | High risk | Approximately 85% progress to colectomy; about 85% sensitivity and 75% specificity for steroid failure | Plan rescue therapy or surgery now; involve the colorectal team the same day |
What the Ho Index needs (3 inputs)
- Mean daily stool frequency over the first 3 days
- A mean across three days rather than a single day's count, which is a real difference from the Travis criteria. Bands are under 4 (0 points), 4 to under 6 (1), 6 to under 9 (2), and 9 or more (4).
- Colonic dilatation greater than 5.5 cm
- On plain abdominal radiograph. Worth 4 points — as much as the highest stool-frequency band, and enough to reach the high-risk threshold by itself.
- Albumin below 30 g/L (3 g/dL) on admission
- The admission value, not the day 3 value. Worth 1 point. It is the lightest item, but it captures nutritional depletion and disease chronicity that nothing else in the score sees.
What it returns
- Total score, 0 to 9
- Graded rather than binary, which is the main structural difference from the Travis criteria.
- Risk band and associated colectomy risk
- 0–1 low at about 11%, 2–3 intermediate at about 45%, 4 or more high at about 85%.
- The item-by-item breakdown
- Shown so it is visible when a score is being driven entirely by colonic dilatation, which changes the urgency more than the number alone conveys.
How it is calculated
The three variables measure different failures, which is why they combine usefully. Stool frequency is the direct readout of how much colon is still inflamed and not absorbing, and it moves quickly when steroids work. Colonic dilatation is a structural finding entirely independent of that: it means the muscular wall is losing tone and the inflammation has become transmural, which is a different and more dangerous process than severe mucosal disease alone — hence four points, and hence the fact that it reaches the high-risk band by itself. Albumin is the slowest of the three and reflects something neither of the others does: sustained catabolism, protein loss through an inflamed colon, and the nutritional state the patient will be in if surgery becomes necessary. Its low weight is appropriate — it rarely changes the band alone — but its presence is what allows the score to distinguish a patient who has been unwell for weeks from one who deteriorated over days with the same stool count. Taking a three-day mean for stool frequency rather than a single day's count is a deliberate smoothing choice, trading the sensitivity of a single reading for stability against a spurious good or bad day.
Facts & figures
| Item | Condition | Points |
|---|---|---|
| Mean daily stool frequency | Under 4 | 0 |
| 4 to under 6 | 1 | |
| 6 to under 9 | 2 | |
| 9 or more | 4 | |
| Colonic dilatation | Greater than 5.5 cm | 4 |
| Albumin on admission | Below 30 g/L (3 g/dL) | 1 |
There is no 3-point stool band — the scale jumps from 2 to 4 at nine stools. Maximum total 9.
| Ho index | Travis (Oxford) | |
|---|---|---|
| Output | Graded, 0–9 | Binary |
| Stool measure | Three-day mean | Day 3 count |
| Inflammatory marker | None | CRP above 45 mg/L |
| Colonic dilatation | 4 points — reaches high risk alone | Not considered |
| Nutritional marker | Albumin, 1 point | Not considered |
| High-risk prediction | Approximately 85% colectomy at score ≥ 4 | Approximately 85% colectomy on that admission |
They converge on the same headline figure by different routes. The disagreements are informative: Ho sees a dilating colon that Travis misses, and Travis sees a persistently raised CRP that Ho does not measure.
Evidence
Derivation — Edinburgh, Ho and colleagues, 2004
2004167 consecutive patients with severe ulcerative colitis recruited between January 1995 and March 2002, with multiple logistic regression applied to parameters recorded within the first three days of medical therapy.
Aggregate scores of 0–1, 2–3 and 4 or more corresponded to colectomy risks of approximately 11%, 45% and 85%. A threshold of 4 on day 3 gave roughly 85% sensitivity and 75% specificity for failure of intravenous corticosteroids.
The comparator at the same timepoint — Travis, 1996
199651 consecutive episodes of severe colitis in Oxford, producing a binary day 3 rule from stool frequency and CRP.
Predicted colectomy on that admission in approximately 85% — the same headline figure reached from a different set of variables, without any assessment of colonic dilatation.
The population it applies to — Truelove and Witts
1955The 1955 criteria defining acute severe ulcerative colitis and determining who is admitted for intravenous corticosteroids in the first place.
Remain the entry criteria; the Ho index is a day 3 checkpoint within that admission rather than a diagnostic instrument.
How it compares
Ho Index vs Travis (Oxford) criteria
The same question on the same day — graded versus binary, and each sees something the other cannot.
Travis uses the day 3 stool count and CRP and gives a yes or no; Ho uses a three-day mean stool frequency, colonic dilatation and albumin and gives 0–9. Both converge on roughly 85% colectomy risk at their respective thresholds, reached by different routes. The gaps are the point: Ho counts colonic dilatation, which Travis ignores entirely, while Travis measures CRP, which Ho does not. A patient with a settling stool frequency and a persistently high CRP is caught by Travis and missed by Ho; a patient with a dilating colon and modest diarrhoea is the reverse. Running both at the day 3 checkpoint costs nothing.
Ho Index vs Truelove and Witts criteria
Truelove and Witts defines the admission; the Ho index assesses whether treatment is working three days into it.
The two are sequential and frequently confused because both use stool frequency. Truelove and Witts identifies acute severe ulcerative colitis at presentation — six or more bloody stools a day plus a systemic feature — and triggers admission for intravenous steroids. The Ho index is scored on day 3 of that treatment and predicts steroid failure. It was derived in patients already defined as severe, so applying it outside that population is outside what it was built for.
Ho Index vs PUCAI
The paediatric equivalent decision point — same logic, different instrument and different day.
PUCAI is used in children with acute severe colitis and is assessed at days 3 and 5 of intravenous steroids to guide rescue therapy, filling the same role the Ho index and Travis criteria fill in adults. It is a symptom-based activity index rather than a risk score, and it uses different thresholds at each timepoint. The shared principle is that the decision to escalate should be made on a scheduled early checkpoint rather than when failure becomes self-evident.
Pearls & pitfalls
- Colonic dilatation alone scores 4 and reaches high risk by itself — read the breakdown, not just the total.
- The stool figure is a three-day mean, not the day 3 count. This differs from the Travis criteria and the two are easily conflated.
- Albumin is the admission value, not the day 3 value.
- There is no 3-point stool band; the scale jumps from 2 to 4 at nine stools.
- The published stool bands overlap at 6 and 9; read as half-open intervals, which is the only partition giving a maximum of 9.
- Toxic megacolon is a clinical emergency in its own right and does not need a score to justify acting on it.
- The intermediate band of 2–3 is the least decisive; cross-check against the Travis criteria, which use CRP.
- The index does not measure CRP at all, so a patient with a persistently raised inflammatory response and few stools may score low.
- A low score is not reassurance — the day 7 checkpoint still applies.
- Prescribe thromboprophylaxis. Acute severe colitis is strongly prothrombotic and bloody diarrhoea is not a contraindication.
Critical actions
- Confirm the patient meets Truelove and Witts criteria for acute severe colitis before applying the index.
- Record a genuine three-day mean stool frequency rather than the day 3 count alone.
- Obtain a plain abdominal radiograph and measure the transverse colon.
- Use the admission albumin, and record it separately if the day 3 value differs.
- Send stool for C. difficile toxin and consider CMV assessment where the trajectory stalls.
- Check thromboprophylaxis is prescribed and being administered.
- Involve the colorectal surgical team on the day a score of 4 or more is reached.
- Cross-check against the Travis criteria, particularly in the intermediate band.
- Reassess at day 7 irrespective of the day 3 score.
Why this score exists
Giving colonic dilatation four points is the decision that makes this score worth having alongside Travis, and it is worth appreciating how blunt an instrument that is. Four points is the maximum any single item can contribute, equal to a stool frequency of nine or more, and it reaches the high-risk threshold on its own — so a patient whose diarrhoea is settling, whose albumin is normal, but whose transverse colon measures 6 cm scores exactly the same as one passing ten stools a day. That is not a subtlety lost in the arithmetic; it is the arithmetic making a point. Mucosal inflammation and a dilating colon are different diseases in the same organ, and only one of them can perforate this week. A score that averaged dilatation in with everything else would dilute precisely the finding that should override the rest, and the Travis criteria — which do not look at the abdominal film at all — cannot make the point in any form. The practical corollary is to read the breakdown rather than the total: a 4 built from dilatation should move faster than a 4 built from stool frequency, even though the score cannot say so.
About the creator
First author; inflammatory bowel disease, Edinburgh
Led the development of the risk score from the Edinburgh severe colitis cohort.
Senior author; inflammatory bowel disease genetics and outcomes
Supervised the cohort study underlying the index.
Co-author; inflammatory bowel disease
Contributed to the derivation and to subsequent UK guidance on acute severe colitis.
Limitations
- Derived in a single Edinburgh cohort recruited between 1995 and 2002, before infliximab was available as rescue therapy.
- The published stool-frequency bands overlap at 6 and 9 stools, requiring an interpretive decision the paper does not make explicit.
- No inflammatory marker at all — a patient with few stools and a persistently high CRP can score low.
- A three-day mean stool frequency requires accurate daily recording, which is not always available.
- Colonic dilatation is measured on plain radiography, with meaningful interobserver variation around the 5.5 cm threshold.
- Albumin falls for many reasons in acute illness and is not specific to colitis severity.
- The intermediate band spans a wide range of clinical situations and is the least actionable output.
- Predicts colectomy risk but does not indicate surgery, and says nothing about the timing or type of operation.
If you are the patient
When someone is admitted with a severe flare of ulcerative colitis and started on steroids through a drip, the team checks on day three whether it is working. The Ho index is one way of doing that. It adds up three things: how many times a day you have been opening your bowels on average over the first three days, whether an X-ray shows the colon has become widened, and whether a blood protein called albumin was low when you arrived. The total runs from 0 to 9. A low total means most people in that group get better on steroids alone. A total of four or more means most do not, and the team will start planning a second medicine or an operation straight away rather than waiting. Something worth understanding: a widened colon on the X-ray scores four points on its own, which puts you straight into the highest group even if everything else looks reasonable. That is deliberate. A colon that is stretching is a more urgent problem than one that is simply inflamed, and it needs acting on quickly. So if your team seems more concerned after an X-ray than the rest of your progress would suggest, that is why. This score is one input, not a decision. Your team will look at it alongside how you actually seem, other tests, and a similar check called the Travis criteria that uses a blood inflammation marker instead of the X-ray. Do ask whether you are on a blood-thinning injection — it is important during a flare even though you are passing blood — and whether infections that can mimic a flare have been tested for.
Frequently asked questions
What is the Ho index?#
A risk score applied on day 3 of intravenous corticosteroids in acute severe ulcerative colitis. It totals 0 to 9 from three items: mean daily stool frequency over the first three days (0, 1, 2 or 4 points), colonic dilatation greater than 5.5 cm (4 points), and admission albumin below 30 g/L (1 point).
What do the score bands mean?#
In the derivation cohort, 0–1 carried roughly an 11% risk of progression to colectomy, 2–3 about 45%, and 4 or more about 85%. A threshold of 4 gave approximately 85% sensitivity and 75% specificity for failure of intravenous corticosteroids.
Why is colonic dilatation worth 4 points?#
Because it reaches the high-risk threshold on its own, and that is the intended effect. A dilating colon indicates transmural inflammation and loss of muscular tone — a different and more dangerous process than severe mucosal disease — and it can perforate. Weighting it equal to the maximum stool-frequency band prevents it being diluted by otherwise reassuring variables.
How does the stool measurement differ from the Travis criteria?#
The Ho index uses a mean across the first three days; the Travis criteria use the count on day 3 alone. The three-day mean is more stable against a spuriously good or bad day but less sensitive to a sharp change. The two are easily conflated, and using the wrong figure shifts the score.
What are the overlapping stool bands?#
The published bands are stated as under 4, 4–6, 6–9 and 9 or more, so 6 and 9 each appear in two bands. This implementation reads them as half-open intervals — under 4, 4 to under 6, 6 to under 9, and 9 or more — which is the only partition consistent with the stated maximum of 9. At 6 stools the score is 2, and at 9 it is 4.
Should the Ho index or the Travis criteria be used?#
Both, ideally. They ask the same question on the same day and reach similar headline figures, but each sees a variable the other does not: Ho counts colonic dilatation, which Travis ignores entirely, and Travis measures CRP, which Ho does not. A patient with a settling stool frequency and a stubbornly high CRP is caught by one; a patient with a dilating colon and modest diarrhoea by the other.
Does a high score mean surgery is needed?#
No. It predicts colectomy risk rather than indicating surgery. What it should trigger is active planning on that day — rescue therapy with infliximab or ciclosporin considered explicitly, the colorectal team involved while the patient is still well, and C. difficile and cytomegalovirus excluded before non-response is attributed to refractory colitis.
Is a low score reassuring?#
Only partly. It predicts a lower risk of colectomy on that admission but says nothing about the later course, and it does not remove the day 7 checkpoint from the Travis study, where more than three stools daily with visible blood still carries a 40% chance of colectomy over the following months. Daily review continues either way.
References
Clinical practice guidelines
- Lamb CA, Kennedy NA, Raine T, Hendy PA, Smith PJ, Limdi JK, et al. British Society of Gastroenterology consensus guidelines on the management of inflammatory bowel disease in adults. Gut. 2019;68(Suppl 3):s1-s106.
- Rubin DT, Ananthakrishnan AN, Siegel CA, Sauer BG, Long MD. ACG Clinical Guideline: Ulcerative Colitis in Adults. Am J Gastroenterol. 2019;114(3):384-413.