Objectives: Data on the clinical presentation, effects of therapy and prognosis of patients with Crohn's disease are often based on patients from specialized referral centers. We assessed the extent of the selection based on the clinical and demographic characteristics.
Methods: All patients with Crohn's disease presenting to the University Hospital of Regensburg (Medical Department) were analyzed retrospectively with respect to demographic and disease specific characteristics. Only patients diagnosed <2 years before presentation were included in the main analysis. The original data from a population-based, prospectively assembled incidence cohort were available for comparison (EC-IBD, northern centers only, n=475). Age at diagnosis, disease location and behavior were categorized according to the Vienna classification. Differences were examined using chi-square tests.
Main results: At the referral center, 394 patients were treated within a 5-year period. Of these, 116 patients fulfilled the inclusion criteria for the comparative analysis. Sixteen percent of the referral patients were diagnosed at age 40 or older, as compared with 32% in the population-based group (P<0.004). The distribution of disease location, sex, smoking behavior and positive family history was similar in both groups. Among the referral patients, more had fistulas (39% versus 20%, P<0.001). Also, more patients were receiving steroids (49% versus 27%) or other immunosuppressive therapy (12% versus 4%). The selection effects increase with duration of disease.
Conclusions: Patients with late onset of disease, inflammatory only disease behavior and no need for immunosuppression are under-represented at a tertiary referral center.