From the Guidelines
The most appropriate serum blood tests to identify Crohn's disease or ulcerative colitis include a full blood count, C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR) level, serum electrolytes, liver enzymes level, serum albumin, and renal function, as recommended by the WSES-AAST guidelines 1. These tests are essential in assessing the disease activity and ruling out other conditions. The following blood tests are commonly used:
- Complete blood count (CBC) to check for anemia, elevated white blood cell count, and platelet count
- Comprehensive metabolic panel to assess liver function, kidney function, and nutritional status
- CRP and ESR to measure general inflammation in the body
- Albumin levels to assess nutritional status and degree of inflammation
- Specific antibody tests like anti-Saccharomyces cerevisiae antibodies (ASCA) and perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA) can provide additional diagnostic clues. It is also important to note that fecal calprotectin, a stool test, is highly sensitive for intestinal inflammation and often used alongside blood tests 1. These tests should be interpreted together with clinical symptoms, endoscopic findings, and imaging studies, as no single test can definitively diagnose IBD. In clinical practice, the diagnosis of Crohn's Disease and Ulcerative Colitis is based on a set of modalities including clinical, biochemical, endoscopic, radiological, and histological diagnostics rather than a single reference standard 1. In assessing an acute abdomen in patients with IBD, laboratory tests including full blood count, electrolytes, liver enzymes, inflammatory biomarkers such as CRP and ESR, serum albumin, and pre-albumin are mandatory 1. It is also crucial to exclude any infectious diseases by performing blood-, stool cultures, and toxin test for Clostridium difficile 1.
From the Research
Serum Blood Tests for Inflammatory Bowel Disease
The following serum blood tests can be used to identify Crohn's disease, ulcerative colitis, or other inflammatory bowel disease:
- C-reactive protein (CRP) levels: Elevated CRP levels are associated with both Crohn's disease and ulcerative colitis, but are significantly higher in Crohn's disease 2
- Erythrocyte sedimentation rate (ESR): ESR is also higher in Crohn's disease, but does not closely reflect disease activity in individual patients 2
- Serum markers of acute phase response: Other biomarkers of inflammation in UC include platelet count, leukocyte count, and serum albumin and serum orosomucoid concentrations 3
Specific Markers for Ulcerative Colitis and Crohn's Disease
- Perinuclear antineutrophil cytoplasmic antibodies (pANCA): Sensitivity and specificity of the pANCA test for the diagnosis of ulcerative colitis were 61 and 79%, respectively 4
- Serum agglutinating antibodies to anaerobic coccoid rods: Had a sensitivity of 42% and a specificity of 89% for a diagnosis of Crohn's disease 4
- Specific IgG antibodies against a Kd-45/48 immunological crossreactive mycobacterial antigen complex (ImCrAC): Sensitivity of specific IgG antibodies against Kd-45/48 ImCrAC in diagnosing Crohn's disease was 70% and specificity 60% 4
Correlation with Disease Activity
- CRP levels corresponded closely with clinical and pathological indices of relapse, remission, and response to therapy in patients with Crohn's disease 2
- Correlation of ESR and CRP with Crohn's disease clinical, endoscopic, and histologic activity during follow-up depended on their value at diagnosis and mode of analysis 5
- A CRP cut-off of ≥12 mg/L generated an 85% positive predictive value with a sensitivity of 95% and an accuracy of 82% for having a paired ESR of >30 mm/h in patients with acute severe UC 6