The use of proliferating cell nuclear antigen (PCNA) expression and intraepithelial lymphocyte count in the differential diagnosis of inflammatory bowel disease.

Colonic biopsies of 283 patients with Crohn's disease (CD), ulcerative colitis (UC), infectious colitis (IC) lymphocytic colitis (LC) and controls for patients with either CD or UC, matched for age and sex, were evaluated with respect to the number of intraepithelial lymphocytes (IEL) and PCNA (cyclin) positive crypt epithelia. The IEL count of patients with LC differed significantly from all other patient groups, indicating that this condition bears no relation to the other diseases. Our patients with histologic diagnosis of LC had no uniform clinical presentation and the significance of this characteristic increase in IEL is unclear. The mean value of PCNA positive crypt epithelia in the lower crypt half was significantly higher in UC patients than in CD patients. PCNA counts in patients with IC or LC were not different from values in UC patients. PCNA counts in CD patients overlapped frequently with those in UC patients. This parameter thus fails to distinguish between CD and UC in individual patients and, though not investigated by us, is unlikely to be effective in the differential diagnosis in patients with a provisional diagnosis of indeterminate colitis.