TROPONIN LEVEL TESTING - detection from blood

A troponin test measures the level of troponin in the blood, a type of protein found in the muscles of the heart. Troponin isn't normally found in the blood, but when heart muscles are damaged, troponin is send into the bloodstream. As heart damage increases, greater amounts of troponin are released into the blood.

High levels of troponin in the blood may indicate having/having had a heart attack (recently). Cardiac troponin (cTn) is composed of three different subunits: 

- Troponin C (cTnC): binds to calcium ions to produce a conformational change in TnI

- Troponin T(cTnT): binds to tropomyosin, interlocking them to form a troponin-tropomyosin complex

- Troponin I (cTnI): binds to actin in thin myofilaments to hold the actin-tropomyosin complex in place

cTn is present in myocardial cells in the form of the cTnI-C-T complex and free cTnI, which is released into blood circulation when an acute myocardial infarction (AMI) occurs. Then, cTnI-C-T can be further decomposed into the cTnI-C complex and free cTnT, where the cTnI-C complex is the main form in the blood. 

Most quick immunochemical Troponin Tests are lateral flow chromatographic immunoassays used for the qualitative detection of cardiac Troponin I (cTnI) in human serum, plasma or whole blood at a level ≥1ng/mL. This test is very useful in the diagnosis of AMI. 

Normally, the level of cTnI in the blood is very low. cTnI is released into the blood stream in forms of free cTnI and cTnI-C-T complex at 4-6 hours after myocardial cell damage. The elevated level of cTnI could be as high as 50ng/mL during 60-80 hours after AMI and remains detectable for up to 10-14 days post AMI. Therefore, cTnI is a specific and sensitive marker for AMI. 

Work procedure for the troponin tests differ from one test device manufacturer to another. Some tests use the: 2 drops of serum/plasma plus 1 drop of buffer or 5 microliters serum plus 2 drops of buffer (it may also be the case that the test cassette already contains what it needs so no buffer is added, only the sample from the patient). Below is an example of a work procedure for the troponin test:

HELICOBACTER PYLORI ANTIBODY TEST - detection from blood

HELICOBACTER PYLORI ANTIBODY DETECTION - from the serum mainly

Helicobacter Pylori is a gram-negative bacterium that causes inflammation of the stomach lining. The results of affection by this bacterium may lead to the chronic gastritis and is strongly linked to the development of duodenal and gastric ulcers and stomach cancer. 

Helicobacter pylori antibody detection from serum/plasma/whole blood is a rapid qualitative test usually based on the immunochromatographic principle. In this test procedure, anti-human IgG is immobilized in the test line region; after specimen addition, it reacts with the H. pylori antigen coated particles in the test. This mixture migrates chromatographically along the length of the test and interacts with immobilized anti-human IgG. 

If the specimen contains H. pylori antibodies, a coloured line will appear in the test line region indicating a positive result. If the specimen does not contain H. pylori antibodies, a coloured line will not appear in this region indicating a negative result. To serve as a procedural control, a coloured line will always appear in the control line region, indicating that proper volume of specimen has been added and membrane wicking has occurred. 

The serological approaches (such as the quick immunochemical test described above) detect the reaction of patient's immunologic system against the disease however these approaches prevent the specialist to distinguish an active infection or the passed infection. In addition, the antibody titre does not change in the course of treatment.

HELICOBACTER PYLORI ANTIGEN TEST - detection from stool

    Helicobacter pylori antigen quick tests from the stool (faecal material) - see image on the left - are usually based on the immunochromatographic principle. Helicobacter Pylori Antigen Cassette Test is used as a diagnostic tool to qualitatively detect  helicobacter pylori antigens in stool. The antigen detection of helicobacter pylori infection in stool can determine all isotypes of existing organism in the stool sample. 

    

    There are several other improved techniques of helicobacter pylori bacterium detection, besides the quick immunochemical tests; urea breath test is one of these techniques. Giemsa staining procedures specific to Helicobacter pylori should also be mentioned; these are performed through the antral endoscopic biopsy, biopsy culture methods and rapid urea tests. The culturing method requires longer time until obtaining the results. 

FECAL OCCULT BLOOD (FOB) TEST - detection from stool

A faecal occult blood test looks at a sample of the stool (faeces) to check for blood. Occult blood means that you cannot see it with the naked eye. 

When there is blood in the stool, it means there is likely some bleeding in the digestive tract. It may be caused by: polyps, haemorrhoids, diverticulosis, ulcers, colitis. Blood in the stool may also be a sign of colorectal cancer, a type of cancer that starts in the colon or rectum. 

The FOB Rapid Test Kits most commonly involve the immunochromatographic method of detection; is intended for the qualitative detection of faecal occult blood. 

The immunochemical rapid test devices are designed to specifically detect low levels of faecal occult blood (it may be as low as 50ng/mL; hHB ≥ 50 ng/mL).