How to use it
Pick the version first. The full Mayo (0–12) needs a colonoscopy or sigmoidoscopy. The partial Mayo (0–9) drops endoscopy, so you can use it at every visit. The modified Mayo (0–9) drops the physician’s global assessment and is the score most current trials report.
Score symptoms against what is normal for this patient, averaged over the last few days. Trials average daily diary scores (the FDA’s 2022 draft guidance recommends a 7-day window). For bleeding, use the worst bleeding of each day.
Reading the result
| Score | Full Mayo (0–12) | Partial Mayo (0–9) |
|---|---|---|
| Remission | ≤2 and no subscore above 1 | ≤2 and no subscore above 1 |
| Mild | 3–5 | 3–4 |
| Moderate | 6–10 | 5–6 |
| Severe | 11–12 | 7–9 |
The severity bands for both the full and partial Mayo are conventions, widely used but not formally validated. They are useful for following one patient over time. In a 105-patient trial, a fall of more than 2.5 points (so 3 or more) in the partial Mayo best matched patients’ own sense of improvement (Lewis 2008).
For the modified Mayo, remission means stool frequency ≤1, rectal bleeding 0 and endoscopic subscore ≤1. Most phase 3 trials enrol “moderately to severely active” UC as a modified Mayo of 5–9 with an endoscopic subscore of 2 or 3.
Endoscopic improvement is a subscore of 0 or 1. Endoscopic remission is a subscore of 0. STRIDE-II treats endoscopic healing as a long-term target in UC.
Pitfalls
- Friability. In the original 1987 score, mild friability was a 1. Current trials and FDA guidance score any friability as 2, so a “Mayo 1” with friability in an older report is a 2 today.
- Total ≤2 isn’t always remission. A patient with no symptoms but an endoscopic subscore of 2 scores 2 in total but is not in remission.
- The physician’s global assessment is subjective. That’s why the modified Mayo drops it.
- Severe flares in hospital. The Mayo score wasn’t built for acute severe colitis. Use the ASUC tool instead.