Background: We have recently shown that the median diagnostic delay to establish Crohn's
disease (CD) diagnosis (i.e. the period from first symptom onset to diagnosis) in the Swiss
IBD Cohort (SIBDC) was 9 months. Seventy five percent of all CD patients were diagnosed
within 24 months. The clinical impact of a long diagnostic delay on the natural history of
CD is unknown. Aim: To compare the frequency and type of CD-related complications in
the patient groups with long diagnostic delay (>24 months) vs. the ones diagnosed within
24 months. Methods: Retrospective analysis of data from the SIBDCS, comprising a large
sample of CD patients followed in hospitals and private practices across Switzerland. The
proportions of the following outcomes were compared between groups of patients diagnosed
1, 2-5, 6-10, 11-15, and ≥ 16 years ago and stratified according to the length of diagnostic
delay: bowel stenoses, internal fistulas, perianal fistulas, CD-related surgical interventions,
and extraintestinal manifestations. Results: Two hundred CD patients (121 female, mean
age 44.9 ± 15.0 years, 38% smokers, 71% ever treated with immunomodulators and 35%
with anti-TNF) with long diagnostic delay were compared to 697 CD patients (358 female,
mean age 39.1 ± 14.9 years, 33% smokers, 74% ever treated with immunomodulators and
33% with anti-TNF) diagnosed within 24 months. No differences in the outcomes were
observed between the two patient groups within year one after CD diagnosis. Among those
diagnosed 2-5 years ago, CD patients with long diagnostic delay (n = 45) presented more
frequently with internal fistulas (11.1% vs. 3.1%, p = 0.03) and bowel stenoses (28.9% vs.
15.7%, p = 0.05), and they more frequently underwent CD-related operations (15.6% vs.
5.0%, p = 0.02) compared to the patients diagnosed within 24 months (n = 159). Among
those diagnosed 6-10 years ago, CD patients with long diagnostic delay (n = 48) presented
more frequently with extraintestinal manifestations (60.4% vs. 34.6%, p = 0.001) than those
diagnosed within 24 months (n = 182). For the patients diagnosed 11-15 years ago, no
differences in outcomes were found between the long diagnostic delay group (n = 106) and
the one diagnosed within 24 months (n = 32). Among those diagnosed ≥ 16 years ago,
the group with long diagnostic delay (n = 71) more frequently underwent CD-related
operations (63.4% vs. 46.5%, p = 0.01) compared to the group diagnosed with CD within
24 months (n = 241). Conclusions: A long diagnostic delay in CD patients is associated
with a more complicated disease course and higher number of CD-related operations in the
years following the diagnosis. Our results indicate that efforts should be undertaken to
shorten the diagnostic delay in CD patients in order to reduce the risk for progression
towards a complicated disease phenotype.