1st order laboratory parameters – obligatory laboratory tests.
- Small blood count (Hb, platelets, leukocytes) [anemia (anemia), leukocytosis (increase in leukocytes/white blood cells), and thrombocytosis (increase in platelets/platelets) as signs of chronic inflammation are the most common changes in the blood count of patients with Crohn’s disease. MCV and MCH may provide evidence of deficiency]
- ESR (erythrocyte sedimentation rate) or CRP (C-reactive protein) [↑; Note: a negative CRP value does not rule out inflammatory bowel disease (IBD)/one in ten Crohn’s disease patients has no CRP elevation despite active disease (CRP nonresponder)]
- Procalcitonin (PCT) – sensitive biomarker for disease activity in Crohn’s disease; especially in patients with hs-CRP < 19 mg/L.
- Calprotectin (fecal inflammation parameter; activity parameter) – for initial diagnosis and progression assessment, the fecal parameter is superior to inflammatory markers in blood:
- Delineation of noninflammatory causes of gastrointestinal symptoms; normal fecal markers largely exclude active CED (inflammatory bowel disease).
- For Crohn’s recurrence monitoring of patients with intestinal resection (postoperative follow-up: 6 + 12 months after surgery):
- Calprotectin levels > 100 µg/g indicated recurrence with a sensitivity (percentage of diseased patients in whom the disease is detected by use of the test, i.e., a positive test result occurs) of 89% and a specificity (probability that actually healthy individuals who do not have the disease in question are also detected as healthy in the test) of 58% (negative predictive value: 90%)
- Calprotectin level < 51 µg/g predicts persistent revision (negative predictive value: 79%).
- Ferritin – to exclude iron deficiency anemia (anemia due to iron deficiency).
- Vitamin B12 serum level – in Crohn’s disease of the terminal ileum or Z.n. resection of the terminal ileum; determination at least annually.
- Albumin in serum
- Liver parameters – alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), glutamate dehydrogenase (GLDH), gamma-glutamyl transferase (γ-GT, gamma-GT; GGT), AP (alkaline phosphatase), bilirubin [In children, liver puncture (liver biopsy) should be performed if transaminases are unclearly elevated. ]Note: Elevated AP (alkaline phosphatase) (3- to 10-fold) is often suggestive of primary sclerosing cholangitis (PSC).
- Renal parameters – urea, creatinine, possibly cystatin C or creatinine clearance.
- Bacteriological stool examination (including examination for C. difficile) – in the initial diagnosis and in fulminant, that is, exceptionally violent relapse.
Laboratory parameters 2nd order – depending on the results of the history, physical examination, etc. – for differential diagnostic clarification.
- Molecular and serological markers of the disease, such as:
- NOD2, HLA-B27 or TNF (tumor necrosis factor) polymorphisms, or ANCA/ASCA – antibodies against neutrophil granulocytes – are of scientific interest but are not used in acute diagnostics due to lack of diagnostic or therapeutic consequences.
- Auto-Ak (IgA, IgG) against exocrine pancreas – occur in circa 39% of cases in Crohn’s disease.
- 25-OH vitamin D levels [frequently decreased]
- Microbiome analysis (so-called, “Whole Genome Shotgun Sequencing”) [foregrounding: Bacteroidetes].
