Portal:Laboratory tests and methods in Gastroenterology
Overview[✎ edit | edit source]
Laboratory diagnostics in Gastroenterology includes specific screening programs, using modern methods to detect the analytes in stool, function tests and also the non-invasive breath tests to detect hydrogen - H2 or stable isotope of carbon - 13C.
Urea breathing test with 13C marking urea – UBT is a gold standard in diagnosis Helicobacter pylori. Reliable way how to diagnose Helicobacter is non-invasive stool antigen test. Laboratory diagnostics in stomach patology includes also serological tests of stomac mucosa – gastrin-17 level, pepsinogen I and II ratio (pepsinogens A anc C), or H. pylori antigen level, CagA and VacA antigens, funktion test of stomach acidity and test of stomach motility – 13C- octanoic acid breath test (OABT).
Chapter acute pancreatitis contains routine tests and methods for detecting serum levels of amylase and lipase, detecting of macroenzymes such as – makroamylase - macroamylasemia and makrolipase - macrolipasemia, determination of amylase isoensymes in faeces, serum levels of elastase 1 or detecting of trypsin levels. Using of urinary trypsinogen test – human trypsinogen activation peptide – (TAP) and carboxypeptidase B - – (CAPAP-B) in early diagnosis of acute pancreatitis. For severity prediction - especially infectious complications - is prokalcitonin a suitable marker.
Diagnosis of chronic pancreatits is still based on tests on pancreatic exocrine function – secretin-pancreozymin test (SCCK/PZS) as a gold standard. The indirect tests are non-invasive but on the other side they have lower sensitivity – PABA or PLT/pankreolauryl test. Other common tests are elastase1 and chymotrypsin measurement in stool. Modern non-invasive indirect test is 13C-labeled mixed triglyceride breath test (13C MTG-BT).
Differential diagnosis of malabsorption syndrom includes intestinal absorption activity examination – measuring β-carotene levels, β-carotene absorption test or vitamine A absorption test. Routine tolerance test is also urinary D-xylose test or laktose tolerance test. Measurement of intestinal permeability represents one of the potential methods of noninvasive laboratory assessment of gastrointestinal toxicity – laktulose/mannitol test (La/Ma test). Non-invasive breath tests is 13C-laktose breath test or 13C-xylose breath test suitable for small-intestinal stomach bacteria overgrowth detection.
Primary malabsorption syndrome is celiac disease, gluten entheropaty. Laboratory methods offers wide spectrum of screening tests - Endomysial antibodies EmA/IgA, gliadin IgA and IgG antibodies. Determination of antitissue transglutaminase antibodies (AtTGA) is basic and most reliable test. Anti-gliadin a anti-tTG can be also measured in stool.
Laboratory diagnosis of colorectal pathology is focused on colorectal cancer screening. Fecal occult blood tests (FOBT) – guaiac Haemocult test, more sensitive immunochemical blood test – iFOBT and quantitative fecal occult blood test – qi-FOBT. Fecal calprotectin can be useful in determination of inflammatory diseases and tumor activity. Using molecular biology methods allow determination of DNA in stool probe.