Although they are not, by themselves, diagnostic, laboratory tests are recommended to aid in the diagnosis, assessment, and monitoring of disease activity in patients with IBD and those suspected of having IBD. Laboratory findings vary widely in IBD patients, but commonly include anemia, leukocytosis, thrombocytosis, transaminitis, hypoalbuminemia, and elevated inflammatory markers. In addition, IBD patients may be taking medications that increase their infection risk and may produce renal or hepatic injury.21,31,32 Therefore, for most ED patients with IBD, screening laboratory tests should include complete blood cell (CBC) count with differential, comprehensive metabolic panel (CMP), liver function tests, and lipase level. Testing for the inflammatory markers, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), and fecal calprotectin, if available in your institution, may also be useful.
Depending on clinical presentation, consider adding additional laboratory tests to the workup. For example, consider a type and screen or type and cross, stool cultures (bacterial, viral, ova, and parasite) and C difficile toxin assay in the patient presenting with bloody diarrhea, or blood cultures and a lactic acid level in the critically ill patient.
C-Reactive Protein and Erythrocyte Sedimentation Rate Testing
CRP and ESR are acute-phase reactants that rise in the presence of active inflammation (as well as with infection, necrosis, neoplasia, trauma, physiologic stress, and other conditions). CRP has been shown to be more sensitive than ESR and other inflammatory markers in evaluating IBD patients.32-35 However, both CRP and ESR testing seem to be more sensitive for CD than for UC. In the studies examined, 70% to 100% of patients with CD presenting with gastrointestinal symptoms had an elevated CRP compared with 50% to 60% of patients with UC.36 CRP also outperforms other markers with respect to correlation with clinical disease activity.37 Normal CRP and ESR levels do not, by themselves, rule out disease flares or complications. Neither CRP nor ESR are recommended on a routine basis in the ED. They may be useful for long-term management and should be ordered in consultation with the patient's physician.
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