Objective measures of disease activity: Alternatives to symptom indices

Advances in fecal and serum inflammatory biomarkers, endoscopy, and radiology have led to a rapid expansion of modalities for diagnosis and disease activity assessment of Crohn's disease. Although no test is recognized as the most accurate for assessing disease activity, ileocolonoscopy remains the single test that may approach the gold standard for clinical diagnosis. Serum C-reactive protein concentrations have been shown to correlate reasonably well with clinical, endoscopic, and radiologic measures of disease activity, and they appear to have prognostic value in certain settings. Fecal markers of inflammation, such as lactoferrin and calprotectin, are relatively noninvasive ways to determine disease activity and predict clinical relapse. Capsule endoscopy allows visual inspection of previously inaccessible areas of the small intestine and may serve as a useful tool for patients with suspected small bowel involvement but negative results on conventional testing. Computed tomographic (CT) enterography, which entails ingestion of a large volume of a neutral or negative contrast agent and scanning protocols that take advantage of the differences in contrast between the lumen and the bowel wall, appears to be more sensitive than small bowel follow-through for detecting small bowel Crohn's disease and provides extraluminal information. Magnetic resonance enterography employs principles similar to those of CT enterography without exposure to ionizing radiation, and early results are encouraging. We are beginning to accumulate evidence that treatment based on objective measures such as mucosal healing might affect long-term outcomes, but prospective trials of objective marker-directed therapy are required to confirm this hypothesis.