Review: Diagnosis and therapy timing shape IBD outcomes

Delays in diagnosis and delayed initiation of effective therapy remain common in inflammatory bowel disease and have been consistently associated with worse outcomes in Crohn’s disease (CD), whereas evidence supporting early “top-down” treatment in ulcerative colitis (UC) has remained limited, according to a review published in the Journal of Crohn’s and Colitis.

The authors examined diagnostic timelines, clinical consequences of delay, and data supporting early intervention strategies in CD and UC.

Diagnostic delay more pronounced in Crohn’s disease

Diagnostic delay appeared more frequent and prolonged in CD than in UC. Studies cited in the review reported median delays of 5–9 months in European cohorts, with longer delays in some US studies. In lower- and middle-income countries, median delays were 8 months for CD and 3 months for UC.

A pooled analysis of eight studies found that patients with CD whose diagnosis occurred above the 75th percentile for time to diagnosis had 88% higher odds of stricturing disease and 65% higher odds of penetrating complications. Delayed diagnosis was also associated with a twofold increased risk of intestinal surgery.

In UC, associations between diagnostic delay and adverse outcomes were less consistent. One adult study reported a 4.1-fold increase in odds of colectomy with delayed diagnosis, whereas pediatric data did not demonstrate a clear association.

A UK cohort study reported a median time to diagnosis of 15.6 months and found higher rates of emergency hospital admissions among patients with longer delays.

Risk factors for prolonged diagnostic intervals included ileal involvement and age younger than 40 years in CD. Broader cohort data identified female sex, Black and Asian race or ethnicity, obesity, smoking, socioeconomic deprivation, loperamide prescription, and preexisting depression or anxiety as associated with diagnostic delays exceeding 12 months.

Noninvasive testing and streamlined pathways

Fecal calprotectin testing in primary care demonstrated negative predictive values of 98% in patients with alarm symptoms and 99% in those without alarm symptoms for distinguishing IBD from functional disorders. Positive predictive values were 50% and 27%, respectively.

In a validation study, combining fecal calprotectin with a Red Flags Index questionnaire increased sensitivity for CD detection from 50% to 100% and improved positive predictive value. A “straight-to-test” colonoscopy pathway reduced time from referral to treatment from 177 days to 24 days.

Evidence for earlier therapy in CD

The authors described a proposed “window of opportunity” hypothesis in CD, reflecting its transmural inflammatory biology and risk of progressive structural damage.

In the CALM randomized trial of patients with disease duration of one year or less, 46% of patients assigned to biomarker-driven tight control achieved mucosal healing without deep ulcers at 48 weeks.

Meta-analyses cited in the review found that anti–tumor necrosis factor (anti-TNF) therapy initiated within three years of diagnosis was associated with reduced abdominal surgery and disease progression. Another analysis defining early biologic therapy as within two years of diagnosis reported higher remission rates.

In a retrospective cohort, biologic initiation within 12 months of diagnosis was associated with higher rates of transmural healing. Transmural healing was linked to lower risks of bowel damage progression (adjusted hazard ratio, 0.28) and CD-related surgery (adjusted hazard ratio, 0.21).

The PROFILE trial enrolled patients shortly after diagnosis (median 12 days) and compared combination infliximab plus immunomodulator therapy with accelerated step-up treatment. Sustained steroid- and surgery-free remission occurred in 67% of patients in the top-down group versus 15% in the step-up group at 48 weeks.

In pediatric CD, early anti-TNF therapy was associated with an 82% reduction in the odds of developing fistulizing perianal disease.

Health economic analyses suggested that early biosimilar anti-TNF therapy may be cost-effective, with reductions in hospitalizations and surgeries offsetting drug costs.

Mixed data in UC

In contrast, an individual participant data meta-analysis did not demonstrate a consistent increase in remission rates among patients with shorter disease duration at treatment initiation in UC. Retrospective studies found no clear differences in hospitalization or colectomy rates between early and delayed anti-TNF initiation. Similarly, early vedolizumab initiation (within 30 days of diagnosis) did not significantly reduce nonresponse rates.

The authors suggested these differences may reflect the predominantly mucosal inflammation in UC and its generally less progressive course compared with CD.

“Early effective therapy and treating early in the disease course has consistently been associated with improved outcomes in Crohn’s disease,” the authors wrote, while noting that “the data for early treatment in UC have been more equivocal.”

They concluded that improving outcomes in IBD requires timely recognition, diagnosis, and initiation of appropriate therapy.

The authors reported relevant disclosures in the original publication.