New consensus recommendations regarding diagnostic criteria for acute severe ulcerative colitis (ASUC) suggest much-needed updates to commonly used existing criteria that date back to the 1950s, importantly including guidance on issues such as corticosteroid use. 

“This consensus provides new diagnostic criteria for ASUC in the modern therapeutic era that can be applied to patients already in receipt of outpatient treatments,” report the authors of the criteria, published in Clinical Gastroenterology and Hepatology. 

“These criteria include additional clinical and laboratory parameters for validation in prospective studies,” they added.

ASUC, an inflammatory condition of the colon and rectum, can represent a medical emergency, often resulting in hospitalization and the need for colectomy, and potentially leading to mortality.

Timely diagnosis can be critical in providing the appropriate treatment and ruling out issues such as enteric infections; however, the current diagnostic measures commonly used in clinical practice are based largely on the Truelove and Witts criteria, despite the criteria dating to 1955 and being shown in recent years to have poor diagnostic accuracy.

Corticosteroid Use, Other Factors

Among the most notable changes in care that warrant consideration in criteria include the routine use of corticosteroids in ASUC.

“Outpatient corticosteroids and advanced therapies may attenuate clinical signs and symptoms and laboratory parameters to below the thresholds specified in the Truelove and Witts criteria, whereas many of these patients would otherwise meet the criteria in the absence of corticosteroid exposure,” the authors noted.

Furthermore, updated criteria are needed to consider laboratory measures of severity, biomarkers such as C-reactive protein (CRP) and radiologic or endoscopic findings. 

To update the criteria, a Delphi panel was assembled consisting of European, North American, and Asia-Pacific gastroenterologists, representing the Refined Evaluation Framework and INvEstigations for Diagnostics in ASUC Working Group. 

Key Major and Minor Criteria

Broadly, for patients already receiving outpatient treatment, the group achieved consensus that a diagnosis could be based on any two of the three major criteria together with at least two minor criteria. Modified criteria were proposed for patients receiving high-dose corticosteroids.

The three key major criteria include having CRP levels at least two times the upper limit of normal (ULN); six or more bowel movements per 24 hours; and 50% or more of bowel movements containing visible blood per 24 hours.

The two minor criteria include having at least two of the following: low albumin, increased heart rate, nocturnal bowel movements, low hemoglobin, increased body temperature, or elevated leukocyte count, among patients treated with advanced therapy/corticosteroids. 

Importantly, patients on high-dose corticosteroids represent a subgroup who require different thresholds. These include having CRP at least 1 x the ULN and having 33% or more bowel movements with visible blood per 24 hours.

The Working Group further agreed that an ASUC diagnosis should be confirmed by endoscopy and, importantly, should exclude the presence of cytomegalovirus infection.

Additionally, radiologic methods should be utilized to support the exclusion of toxic megacolon.

Notable Exclusions

While erythrocyte sedimentation rate (ESR) and fecal calprotectin (FCP) are biomarkers reported to have roles in diagnosing ASUC, the two were determined to not be useful, with FCP rapid testing not widely available in clinical practice, and CRP considered “easier to measure than ESR in a clinical setting and [possibly having] higher specificity,” the panel concluded.

And while there was agreement on the importance of endoscopy in confirming a diagnosis of ASUC, consensus was not reached on specific endoscopic findings that would confirm a diagnosis.

The panel further agreed that the Mayo Endoscopic Score represented the most used scoring system in clinical practice, above the Ulcerative Colitis Endoscopic Index of Severity; however, neither of the scores is considered to be sufficiently validated for the diagnosis of ASUC.

Of note, “studies show that patients with acute severe ulcerative colitis may remain within Mayo 3 despite responding to therapy, illustrating the wide spectrum of endoscopic severity included within this category,” they explained, with no consensus regarding the need for a new scoring system.

Other Caveats

The panel noted that, with ASUC in some cases representing a medical emergency, the assessment of some lab measures, such as CRP, may not always be possible or could delay needed interventions.

“In such circumstances, the decision to admit a patient with suspected acute severe ulcerative colitis should be guided by clinical judgement to avoid postponing urgent treatment,” they explained.

And for patients treated with high-dose corticosteroids, the presence of the first three major criteria, alone, is considered acceptable in a diagnosis of ASUC, with the panel agreeing that “the thresholds for CRP and blood in bowel movements in this population would be lower than for the other patient groups, and versus the Truelove and Witts criteria, further supporting that these criteria may be too stringent for use in this population.”

The panel further noted that, with approximately a third of untreated patients presenting with ASUC as a first manifestation of ulcerative colitis, representing more of a diagnostic challenge, the diagnostic work-up for ASUC may need to be more extensive, with a heavy focus on areas of excluding other diagnoses and endoscopic findings.

The Working Group concluded that it “recognizes the considerable challenges in the diagnosis of acute severe ulcerative colitis, including ongoing uncertainty in the best approach to diagnose acute severe ulcerative colitis in untreated patients.”

They added that “further research is needed in untreated patients and to validate the areas of consensus obtained in this Delphi study in real-world practice.”

Commenting on the report, Casper Steenholdt, MD, PhD, clinical professor and chief physician in the Department of Medical Gastroenterology, Odense University Hospital in Odense, Denmark, said the criteria rightfully address key issues, with the important caveat of requiring outside validation.

“Many patients admitted today have already received corticosteroids or advanced therapies, which may attenuate systemic manifestations,” Steenholdt told Medscape Medical News. “The proposed criteria therefore add clinically relevant dimensions,” he said.

However, echoing the authors’ note of needed validation, he agreed that “consensus is not the same as diagnostic validation. Their sensitivity, specificity, prognostic validity, and clinical consequences have not yet been established prospectively.”

Similar Outcomes Observed

In his own research, Steenholdt and colleagues reported on a cohort of 109 patients hospitalized with ASUC.

They found that, of the patients, 73% fulfilled Truelove and Witts criteria and 27% did not, yet the disease course and outcomes were similar between the two groups, including in colectomy-free survival and prognostic indices.

“Despite lower CRP and less pronounced anemia and hypoalbuminemia at admission, these patients had rates of rescue therapy, colectomy, readmission, and subsequent TNF inhibitor exposure that were not statistically different from those of patients meeting the traditional criteria,” Steenholdt explained, noting that similar findings were observed in an independent validation cohort.

“These findings support the need to broaden or refine the definition, but our study did not establish how acute severe ulcerative colitis should be redefined,” he said.

Guidelines?

Updated ulcerative colitis guidelines from the American College of Gastroenterology, published in 2025, as well as guidelines from other organizations, address more recent advances, but those, too, are lacking in full validation, Steenholdt noted.

“Updated management guidelines do not necessarily provide a prospectively validated replacement for the diagnostic boundary established by Truelove and Witts,” Steenholdt explained.

“The traditional criteria remain widely used to define acute severe ulcerative colitis, particularly in clinical trials and treatment algorithms.”

The proposed criteria require prospective validation against clinically meaningful outcomes, including the need for rescue therapy, colectomy, and complications, Steenholdt noted.

Furthermore, “there was no consensus on a definitive diagnostic combination for untreated patients, [and] quantitative thresholds were not established for several of the minor criteria, while no specific endoscopic threshold was agreed upon.”

“These features may leave considerable room for variation in implementation.” 

Until then, however, Steenholdt urged that “clinicians should not withhold admission, close monitoring, or timely treatment escalation from a patient with a severe ulcerative colitis flare solely because the patient does not fulfill every component of the 1955 Truelove and Witts definition.”

The consensus panel was sponsored by AbbVie, which also invited its co-chairs. To mitigate any potential bias, the co-chairs did not actively participate in the consensus voting, AbbVie reported. “The sponsor conducted a compliance review of final statements but did not actively modify statements or participate in the delivery of the Delphi panel,” the company reported. Steenholdt reported receiving speaker fees from Eli Lilly, Orion Pharma, Takeda, and Janssen; consultancy fees from Takeda and Orion Pharma; and service on an advisory board for Eli Lilly. His study of non-Truelove and Witts criteria did not receive industry funding.