Laboratory assessment of inflammatory bowel disease

Presently there are no specific laboratory tests to diagnose inflammatory bowel disease (IBD). Nonspecific tests to differentiate diarrhea due to mucosal injury from that occurring in patients with normal bowel mucosa (eg, fecal occult blood, leukocytes, etc) are not helpful. Tests to exclude infections agents are very important, since the clinical and radiological appearance of these may mimic IBD, and patients with IBD may suffer from superinfection. There are no laboratory tests which can differentiate Crohn's colitis from ulcerative colitis (UC). The tests used in the assessment and management of severely ill patients (Hgb, WBC, electrolytes, etc) are important, since abnormalities need to be corrected on an ongoing basis. The tests used to assess nutritional status are of little clinical value, since "clinical assessment" is as good as the laboratory assessment. Estimation of disease activity by tests is rarely better than the judgment of the clinician. Workup for malabsorption in Crohn's disease and the assessment of absorptive capacity of the terminal ileum are important for proper planning of management. Laboratory tests are also useful in clarifying the nature of some complications (eg, anemias and joint diseases).