Laboratory methods in gastroenterology

Laboratory diagnostics in gastroenterology includes specific screening programs, non-invasive examination programs using modern methods of detection of analytes in stool, functional diagnostics, also in non-invasive form, using breath tests with detection of hydrogen – H₂ or stable carbon – ¹³C isotope.

Diagnosis of Helicobacter pylori infection[edit | edit source]

Carbon ¹³C-labeled urea breath test – UBT is the gold standard for diagnosis of Helicobacter pylori infection. A reliable variant is a non-invasive stool antigen detection test H. pylori. Laboratory diagnosis of gastric pathology includes serological tests of the condition of the gastric mucosa - the level of gastrin-17, the ratio of pepsinogens I and II (pepsinogens A a C), or the level of antibodies against H. pylori, CagA and VacA antigens, gastric acidity functional test and gastric motility test – sodium ¹³C-oktanoate breath test (OABT).

The issue of acute pancreatitis includes routine methods for the determination of amylase and lipase in serum, detection of macroenzymes – makroamylase and makrolipase, detection of amylase in stool, determination of pancreatic elastase 1 in serum, or trypsin levels. Early diagnosis of acute pancreatitis is offered by the determination of trypsinogen in urine, resp. trypsinogen activating peptides - TAP and carboxypeptidase – CAPAP. The level of procalcitonin is a suitable marker for assessing the severity of acute pancreatitis, especially infection.

The gold standard for the diagnosis of chronic pancreatitis is still a direct test of exocrine pancreatic function – the secretin-pancreasymin test (SCCK/PZS). Indirect tests are non-invasive, but have significantly lower reliability – PABA or PLT / pancreolauryl test, determination of pancreatic enzymes in stool – chymotrypsin a elastase 1. A modern, non-invasive and indirect test is the ¹³C-MTG breath test.

Differential diagnosis of malabsorption syndrome includes assessment of the absorption activity of the intestinal mucosa by detecting the level of β-carotene, případně zátěžovým testem s β-karotenem or vitamin A. A routine tolerance test is the detection of D-xylose in urine or lactose tolerance test. There are several test variants to assess intestinal permeability, such as the lactulose / mannitol test (La/Ma test). Non-invasive breath tests are the ¹³C-laktose breath test or the ¹³C-xylose breath test suitable for the detection of bacterial overgrowth in the small intestine.

The primary malabsorption syndrome is celiac disease, gluten enteropathy. Laboratory diagnostics offers a wide range of screening tests with the detection of antibodies to endomysium EmA/IgA, gliadin IgA and IgG. The basic, most reliable test is the detection of antibodies to tissue transglutaminase atTG IgA and IgG class. Anti-gliadin and anti-tTG can also be determined in a stool sample..

Laboratory diagnostics of colon pathology is focused mainly on colorectal tumor screening, faecal occult blood tests, screening - guaiac Haemoccult test – gFOBT, more sensitive immunochemical test – iFOBT, and quantitative determination of hemoglobin in stool – qi-FOBT. The activity of inflammatory diseases and tumors can also be monitored by detecting calprotectin in the stool. The development of molecular biology makes it possible to isolate DNA from a stool sample and to determine a number of genetic markers.

with permission of the author taken from KOCNA, Petr. GastroLab : MiniEncyclopedia of laboratory methods in gastroenterology [online]. ©2002. The last revision 2011-01-08, [cit. 2011-03-04]. <http://www1.lf1.cuni.cz/~kocna/glab/glency1.htm>.