From the Guidelines
Blood tests recommended for patients suspected of having inflammatory bowel disease (IBD) include complete blood count (CBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), comprehensive metabolic panel, albumin, and fecal calprotectin, as stated in the most recent guidelines 1. These tests are essential for assessing disease activity, nutritional status, and potential complications. A CBC can detect anemia, which is common in IBD due to chronic blood loss or malabsorption of iron and vitamins, while also showing elevated white blood cell counts during inflammation. CRP and ESR are inflammatory markers that rise during active disease, helping to assess inflammation severity. Liver function tests and albumin levels are important as IBD can affect liver function and cause protein loss. Fecal calprotectin, though technically not a blood test, is highly sensitive for intestinal inflammation and helps differentiate IBD from irritable bowel syndrome.
Some key points to consider when ordering blood tests for IBD include:
- Monitoring for vitamin D and iron deficiency, as recommended by the AGA 1 and ESPEN 1
- Checking for micronutrient deficiencies, such as zinc and folate, which are common in IBD patients 1
- Using serum proteins, such as albumin, with caution, as they can be affected by inflammation 1
- Considering the use of multivitamin supplements to correct deficiencies, but also being aware of the potential for poor compliance and the need for specific replacement regimens 1
Additional tests may include:
- Vitamin B12, folate, and iron studies to evaluate nutritional status
- Perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA) and anti-Saccharomyces cerevisiae antibodies (ASCA), which can help distinguish between ulcerative colitis and Crohn's disease
- Blood cultures and stool tests to rule out infectious causes, such as Clostridium difficile 1
It is essential to perform these tests before initiating treatment to establish baseline values and monitor disease activity over time, as recommended by the guidelines 1.
From the Research
Blood Tests for Inflammatory Bowel Disease (IBD)
The following blood tests are recommended for patients suspected of having inflammatory bowel disease (IBD):
- C-reactive protein (CRP) 2, 3, 4, 5
- Erythrocyte sedimentation rate (ESR) 2, 3, 6, 4, 5
- Albumin 2, 3
- Platelet count (PLT) 2, 3
- Hemoglobin 2, 3
- Mean corpuscular volume (MCV) 4
- White blood cell count 4
- Serum albumin 4
- Total serum protein 4
- Estimated serum globulin 4
- Neutrophil to lymphocyte ratio (NLR) 3
- Platelet to lymphocyte ratio (PLR) 3
- Lymphocyte to monocyte ratio (LMR) 3
- Red blood cell distribution width (RDW) 3
Rationale for Each Test
- CRP and ESR are markers of inflammation and can be elevated in patients with active IBD 2, 3, 5
- Albumin and hemoglobin can be decreased in patients with active IBD due to malabsorption and chronic inflammation 2, 3
- PLT can be elevated in patients with active IBD due to inflammation 2, 3
- MCV, white blood cell count, serum albumin, total serum protein, and estimated serum globulin can be abnormal in patients with IBD due to malabsorption and chronic inflammation 4
- NLR, PLR, LMR, and RDW can be elevated in patients with active IBD due to inflammation 3
Combination of Blood Tests
- The combined use of fecal biomarkers and blood indexes is superior to the use of fecal biomarkers alone in identifying endoscopically active disease 2
- The combination of CRP and albumin (CRP/ALB ratio) can be used to differentiate between active and inactive IBD 3
- The combination of ESR and hemoglobin can be used as a screening strategy for IBD, with a higher positive predictive value and sensitivity than commercial serologic testing 6