1st order laboratory parameters – obligatory laboratory tests.
- Small blood count [leukocytosis (increase in leukocytes/white blood cells), thrombocytosis (increase in platelets/platelets)]
- ESR (erythrocyte sedimentation rate) or CRP (C-reactive protein) ↑
- Calprotectin (fecal inflammation parameter; activity parameter; stool sample) – for initial diagnosis and progression of inflammatory bowel disease (IBD), the stool parameter is superior to inflammatory markers in the blood; delineation of non-inflammatory causes of gastrointestinal symptoms; normal fecal markers largely exclude active IBD.
- 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 [increase in liver and cholestasis parameters in hepatobiliary extraintestinal manifestations].
- Ferritin – to exclude iron deficiency anemia (anemia due to iron deficiency).
- Vitamin B12 and folic acid serum levels – for megaloblastic anemia (anemia (anemia) caused by a deficiency of vitamin B12 or, less commonly, folic acid deficiency).
- Infection diagnosis due totherapy planning, steroid refractory course and weakened immune system:
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- Tuberculosis diagnostics (see below Tb) due toTb risk under TNF antibodies.
- Epstein-Barr virus (EBV) serology due toEpstein-Barr virus (EBV)-negative patients, these have a risk of lymphoproliferative disorders or macrophage activation syndrome under azathioprine → waiver of azathioprine therapy in EBV negativity.
- Cytomegalovirus (CMV) serology in steroid-refractory course → cause may be CMV reactivation
- Stool sample (microbiological diagnostics) – to detect bacteria.
- Bacteriological stool examination must be performed in the initial diagnosis and fulminant relapse. Here, the bacterium Clostridium difficile and CMV (cytomegalovirus) are of particular importance.
- Exclusion of concomitant infections such as hepatitis and HIV infection → weakened immune system and thus a higher risk of infection.
Laboratory parameters 2nd order – depending on the results of the history, physical examination, etc. – for differential diagnostic clarification.
- AP (alkaline phosphatase), γ-GT (gamma-glutamyl transferase) – for the detection of primary sclerosing cholangitis (bile duct inflammation).
- Autoimmune serology: pANCA (perinuclear antineutrophil cytoplasmic antibody), ASCA (anti-Saccharomyces cerevisiae antibody).
- 25-OH vitamin D levels [frequently decreased].
- Microbiome analysis (so-called, “Whole Genome Shotgun Sequencing”) [foregrounding: Bacteroidetes].
