From the Guidelines
Blood tests for evaluating inflammatory bowel disease (IBD) should include a full blood count, serum C-reactive protein level, erythrocyte sedimentation rate, serum electrolytes, liver enzymes level, serum albumin, renal function, and fecal calprotectin level, as recommended by the most recent guidelines 1. When suspecting IBD based on symptoms like chronic diarrhea, abdominal pain, weight loss, or rectal bleeding, these tests should be ordered to assess inflammation and disease activity. Additional important tests include:
- Comprehensive metabolic panel to check liver and kidney function
- Albumin to assess nutritional status
- Fecal calprotectin, which is highly specific for intestinal inflammation
- Serologic markers such as anti-Saccharomyces cerevisiae antibodies (ASCA) and perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA) to help differentiate between Crohn's disease and ulcerative colitis
- Vitamin B12, folate, and iron studies to check for malabsorption and anemia These blood tests are valuable screening tools but cannot definitively diagnose IBD alone; endoscopy with biopsy remains the gold standard for diagnosis, as supported by previous studies 2, 3, 4. Regular monitoring of these markers is also important for assessing disease activity and treatment response in established IBD patients. It is also crucial to exclude any infectious diseases by performing blood, stool cultures, and toxin test for Clostridium difficile, as recommended by the guidelines 1.
From the Research
Blood Tests for Inflammatory Bowel Disease
- Blood tests are essential in evaluating inflammatory bowel disease (IBD) as they help identify anemia, which is a common extraintestinal manifestation of IBD 5, 6.
- Anemia in IBD can be caused by iron deficiency, anemia of chronic disease, vitamin B12 and folate deficiency, hemolytic anemia, and medications such as azathioprine and sulfasalazine 6.
- Diagnostic evaluation for anemia in IBD includes a complete blood count, iron indices, inflammatory markers, and vitamin B12 and folate levels 6, 7.
- Laboratory tests can also be used to monitor disease activity, medication response or toxicity, surveillance of infectious complications, and detection of nutritional deficiencies in IBD patients 8.
Types of Anemia in IBD
- Iron deficiency anemia is the most prevalent type of anemia in IBD patients, followed by anemia of chronic disease 5, 7.
- Anemia of chronic disease is mainly driven by the effects of inflammatory mediators on iron metabolism and erythropoiesis, and treatment requires control of disease activity 6.
- Vitamin B12 and folate deficiency can also cause anemia in IBD patients, and laboratory tests can help identify these deficiencies 6, 7.
Laboratory Tests in IBD
- Laboratory tests, including blood tests, are valuable adjuncts to clinical assessment with imaging, endoscopic, and histopathological examination in the management of IBD 8.
- Routine use of laboratory tests can help clinicians avoid reactivation of life-threatening infections, detect vitamin deficiencies, and monitor medication response or toxicity 8.
- Therapeutic drug monitoring (TDM) is an evolving topic in the era of biologics, and laboratory tests can help clinicians optimize treatment and minimize toxicity 8.