From the Guidelines
For an acute ulcerative colitis (UC) flare, I recommend obtaining a complete blood count (CBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), comprehensive metabolic panel (CMP), and stool studies including Clostridioides difficile testing, stool culture, and fecal calprotectin. These tests help assess disease severity, identify complications, rule out infections that can mimic or trigger flares, and establish a baseline for treatment monitoring 1. The CBC can reveal anemia from chronic blood loss or inflammation, leukocytosis suggesting inflammation or infection, and thrombocytosis indicating active disease. CRP and ESR provide objective measures of inflammation, with CRP being more sensitive to acute changes. The CMP evaluates electrolyte imbalances, kidney function, and albumin levels, which may be decreased in severe disease. Stool studies are crucial to exclude infectious causes that would require different management approaches, such as Clostridium difficile and Cytomegalovirus 1. Fecal calprotectin specifically correlates with intestinal inflammation and helps distinguish between active UC and irritable bowel syndrome.
Key Laboratory Tests
- Complete blood count (CBC) to assess anemia, leukocytosis, and thrombocytosis
- C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) to measure inflammation
- Comprehensive metabolic panel (CMP) to evaluate electrolyte imbalances, kidney function, and albumin levels
- Stool studies, including:
- Clostridioides difficile testing
- Stool culture
- Fecal calprotectin to assess intestinal inflammation
These laboratory tests should be obtained promptly to guide appropriate treatment decisions and monitor response to therapy, as recommended by the WSES-AAST guidelines for the management of inflammatory bowel disease in the emergency setting 1.
From the Research
Laboratory Tests for Acute Ulcerative Colitis (UC) Flare
- The following laboratory tests are recommended for assessing acute UC flare:
- C-reactive protein (CRP) levels 2, 3, 4, 5
- Erythrocyte sedimentation rate (ESR) 2, 3, 4
- Complete blood count (CBC) parameters, including platelet count, leukocyte count, and neutrophil-lymphocyte ratio (NLR) 3, 4, 5
- Serum albumin levels 3, 4
- C-reactive protein-albumin ratio (CRP/ALB) 4
- Platelet-lymphocyte ratio (PLR) 4
- Mean platelet volume (MPV) 5
- Lymphocyte to monocyte ratio 5
Interpretation of Laboratory Results
- A CRP cut-off of ≥12 mg/L is proposed as an alternative to ESR for defining UC presentation severity 2
- The CRP/ALB ratio is a useful independent predictive biomarker for disease activity in UC 4
- High sensitivity C-reactive protein (hs-CRP), CAR, NLR, and PLR are significantly higher in patients with active UC than in those with mucosal healing 5
- Decreased MPV reflects inflammatory activity in the UC mucosa 5
Clinical Application
- These laboratory tests can be used to assess disease activity, predict disease activation, and monitor response to treatment in patients with acute UC flare 6, 2, 3, 4, 5
- The results of these tests can help guide clinical decision-making, including the need for hospitalization, intravenous corticosteroids, and other treatments 6