general information about the study
Colorectal cancer is one of the most common types of tumors, both in terms of incidence and fatalities. It ranks second in mortality among malignant neoplasms in men and women. Every year there are more than 1 million new cases of the disease worldwide, and the annual death rate exceeds 500,000. The risk of developing the disease increases with age, 90% of those affected are over 55 years of age. According to epidemiological data, heredity is the cause of the development of colorectal cancer in 5-30% of patients. TO hereditary syndromes, in which the risk of developing it significantly increases, include familial adenomatous polyposis, Lynch syndrome, juvenile polyposis and some rarer conditions. A patient's 5-year survival rate depends on the stage of the cancer at the time of diagnosis.
Colorectal cancer develops slowly over several years. The tumor often occurs as a result of the transformation of a polyp of the intestinal mucosa. This process can take from 8 to 12 years. Not all types of polyps can turn into tumors, but their presence, especially in large quantities, significantly increases the risk of developing colorectal cancer. Other precancerous conditions include dysplasia, which is typical for people with ulcerative colitis and Crohn's disease.
In colorectal cancer, blood with feces can be released long before the first symptoms of the disease. Screening examination of feces for occult blood among people at risk helps to diagnose the disease in a timely manner and reduce mortality from colorectal cancer by 15-33%. The effectiveness of such screening has been confirmed by several studies.
To detect hidden blood in stool, guaiac or benzidine tests are most often used, but they require strict adherence to certain rules, in particular following a diet several days before the test. In addition, unlike the guaiac test, modern immunochemical methods are highly sensitive and specific.
The fecal occult blood (FOB) immunoassay test has been proven to be the most convenient test method due to its ease and effectiveness in patient management. It allows you to accurately determine the amount of hemoglobin (Hb) in the stool, without requiring patients to follow a diet or change their lifestyle. The method is based on an antigen-antibody agglutination reaction between the human hemoglobin present in the sample and the anti-hemoglobin antibody on latex particles. Agglutination is measured as an increase at absorbance of 570 nm, the unit of which is proportional to the amount of human hemoglobin in the sample. The study determines hidden blood that has entered the intestinal lumen in the lower parts of the gastrointestinal tract, since hemoglobin from upper sections destroyed when passing through the digestive tract.
A positive test result requires further examination to clarify the reasons, since the source of minor blood loss may be a benign polyp, diverticulum, hemorrhoids or inflammatory bowel disease. On average, 1-5% of people test positive for occult blood, of which 2-10% are diagnosed with cancer, and 20-30% are diagnosed with adenomatous polyps of the colon. At positive reaction carried out for occult blood additional examination to detect cancer, polyp, or other cause of bleeding. To confirm the diagnosis, patients in the absence of contraindications are prescribed colonoscopy, sigmoidoscopy or double contrast radiography. The absence of blood in the stool does not completely exclude the possibility of colorectal cancer, therefore endoscopy is recommended for people at high risk (with a family history) even if negative result analysis.
What is the research used for?
- For screening for colon and rectal cancer.
- For the diagnosis of bleeding from the lower gastrointestinal tract in certain benign and inflammatory diseases (colon polyps, Crohn's disease, ulcerative colitis, haemorrhoids).
When is the study scheduled?
- With preventive annual examination persons aged 50-75 years.
- If you suspect hidden intestinal bleeding.
A rapid test for occult blood in feces can detect the presence of occult bleeding, with a sensitivity of 2 mg of hemoglobin per 100 ml of water. This allows you to determine at home the presence of bleeding into the intestinal lumen that is not detectable by the eye.
The most effective and reliable test issues American company"Biomerica" "EZ Detect". The chromophilic dye tetramethylbenzidine is applied to the test strip; when it comes in contact with hemoglobin, its color changes. At the same time, the cross-shaped window changes color to blue or green. This test can only be ordered through online stores.
There is a domestic budget analogue, which is not as accurate, but it can be purchased at almost all pharmacies. This test is produced by the Med-Express Diagnostics company under the name "Rest assured".
You can also purchase on domestic markets Cito Test FOB to detect hidden blood in stool. The company specializes in express diagnostics of oncological pathology, so the test can be trusted.
Table 1. List of rapid tests for the presence of occult blood in potassium
What diseases can it detect?
- – most common reason the appearance of occult blood;
- – a benign disease, which can also cause hidden bleeding when the polyp is microtraumatized by chyme;
- – bleeding is often obvious;
- – often clinically manifested by the presence of blood streaks in the stool.
The test only determines the presence of blood; a specific disease can only be identified through examination - and others.
- over 40 years of age, especially those with bad habits(alcoholism, smoking);
- with a family history of colon cancer;
- with metabolic syndrome (abdominal obesity);
- with a sedentary lifestyle ( office workers, drivers Vehicle etc.);
- with impaired stool with a tendency to constipation;
- with precancerous intestinal diseases (polyposis, autoimmune inflammatory diseases and so on).
Preparing and conducting the test
The following points should be kept in mind before taking the test:
The test is carried out as follows:
- Unscrew the collection cap.
- Remove the applicator.
- Make sure that the reagent inside the collection does not spill.
- Immerse the applicator in 3-5 areas of the stool being analyzed.
- Remove excess feces from the surface of the applicator with a dry cloth.
- Place the applicator into the collection containing the reagent.
- Shake the collection vigorously to evenly mix the stool with the reagent.
- Open the tablet along the slot.
- Place on a flat, dry surface with the test area facing up.
- Turn the collection over.
- Unscrew the cap (pin-plug).
- Place 2 drops of reagent onto the window of the test plate.
- Wait 5 minutes before assessing the result.
Decoding
Test positive
The appearance of two colored stripes in the test system window. Any intensity of color indicates that there is hidden blood in the stool; the intensity of the color depends on the amount of hemoglobin.
After receiving a positive result, you must urgently consult a doctor for further examination: blood tests, irrigography, colonoscopy and other studies at the discretion of the doctor. The sooner cancer is tested and treated, the greater the likelihood of a successful outcome and increased survival.
Test negative
Only one line in control area C is colored, test strip T remains clear.
If the test was carried out as a screening diagnosis in the presence of clinical manifestations, it is better to contact a specialist and undergo more precise research (see) to determine the causes of complaints. If the test was carried out as an annual screening examination (like fluorography) after 40 years, then the test can be repeated a year later.
conclusions
World practice states that the effectiveness of this test is undeniable. Errors may occur; a more accurate test for diagnosing colon cancer is initial stages is .
If there are clinical manifestations and complaints, you should consult a doctor. The specialist himself may recommend a rapid test for occult blood as a screening. The earlier the diagnosis is made, the more likely it is to receive timely and effective treatment.
Catalog number: 4091-3L Packaging: 20 tests/pack
Reference
There are more than 600,000 cases of colorectal cancer worldwide each year, which is the third most common cancer (1). As with any other variety cancer diseases, detection of foci on early stage significantly increases the survival rate of patients (2). Among people over 45 years of age, 10% have colorectal polyps, of which 1% become cancerous (3). Based on the fact that many polyps larger than 0.5 cm may bleed, fecal occult blood testing appears to be a simple and inexpensive screening method for diagnosing colon cancer compared with colonoscopy. For many years, chemical techniques based on the pseudoperoxidase activity of hemoglobin have been used, the disadvantages of which are low sensitivity and lack of specificity (4). Immunological methods with improved sensitivity and specificity for human blood are now beginning to be used, despite their greater technical complexity compared to other tests (5). Recently, a direct association between fecal hemoglobin concentration and colorectal cancer has been confirmed (6).
Purpose and principle of the method
Quantitative immunochromatographic rapid test for the detection of occult blood in feces. The determination method is based on the use of a specific complex of dye-conjugated mouse monoclonal antibodies to human hemoglobin and immobilized in the test zone of the cassette of monoclonal mouse antibodies to human hemoglobin for its selective identification with a high degree of sensitivity and specificity. After taking a sample with a special syringe containing an extraction solution, a few drops of the resulting fecal extract are placed into the sample well of the test cassette. When the test sample passes through the adsorbent layer, the labeled antibody-dye conjugate binds to human hemoglobin, forming an antigen-antibody complex. This complex binds to antibodies to hemoglobin in the reaction zone, forming a pink band. In the absence of hemoglobin, the line does not form. Continuing to move along the adsorbent layer, the unbound conjugate binds to the reagents in the control zone to form a control band indicating the reactivity of the test. Depending on the blood concentration, lines of varying intensity appear in the test window, which allows you to quantitatively measure hemoglobin using the “Easy Reader” immunochromatographic express analyzer (VEDALAB).
Compound
Test cassettes 20
Sample collection devices (syringe with 2 ml extraction solution) 20
Instruction 1
Stability and storage
1. Store at a temperature of 4 to 30°C in sealed original packaging.
2. Do not freeze!
3. The test is stable until the expiration date stated on the label.
Precautionary measures
This test is for diagnostic purposes only. in vitro and professional use.
When working with samples, wear protective clothing and disposable gloves.
Do not eat, drink or smoke in the area where samples are being handled.
When taking and testing samples, do not touch the mucous membrane of the eyes and nose with your hands.
Do not use the test cassette if its protective packaging is damaged.
Do not use a test cassette that has expired.
The extraction solution may cause irritation to the skin, eyes and mucous membranes. If the solution gets on your skin, wash it off immediately with water.
Waste disposal
All samples should be considered potentially infectious. After completion of the testing procedure, samples should be disposed of with caution and only after sterilization in an autoclave or treatment with 0.5–1% sodium hypochlorite solution for at least 1 hour.
Reagent Preparation
All reagents are ready for use.
Test samples
Feces extract.
Sample collection and preparation
1.Write the patient's name, age, address, and date of sample collection on the sample collection device label.
2.Open the top of the sample collection device, where the sample collection probe is located.
3.Collect a stool sample using the top of the sample collection device by dipping it in 3 different locations of the same stool sample and place it into the device.
4.Place the sample collection probe loaded with sample back into its place in the sample collection device and screw the plug tightly.
5.Store the sample collection device at a temperature of 2-8°C.
Testing procedure
1. Bring all samples and test cassettes to room temperature.
2. Remove the test cassette from its protective packaging.
3. Break off the tip of the sample collection device, dispense 6 full drops of extracted sample (150 µl) into the sample well on the test cassette, allowing the previous drop to be absorbed.
4. Test results in ng/ml are read on the “Easy Reader” device 10 minutes after adding the sample.
A detailed description of the operation of the reader is given in the instructions for the device.
Test characteristics
a) Measuring range
The quantitative result of the test is expressed in ng of hemoglobin per ml of extraction solution. The linear range of results is from 10 to 500 ng/ml, the range is given in the table:
b) Accuracy
The study was conducted on a panel of 24 faecal samples submitted by Bradford Hospital (UK) to the Yorkshire External Quality Assurance System (YEQAS). These samples, containing a known concentration of hemoglobin (in mg/g faeces), were tested by a qualitative visual rapid test and this quantitative test. The results obtained indicate a complete correlation between the results. In addition, the quantitative results correlate well with the amount of hemoglobin (YEQAS data in mg/g feces). In all cases, samples were clearly identified as negative (<10 нг/мл), пограничные (10-25 нг/мл) и позитивные (500-5,000 нг/мл).
c) Sensitivity
Concentrations close to 5 ng/ml are determined by the device. In this case the result is shown as "<10 ng/ml». Результаты выше 100 нг/мл рассматриваются как патологические.
d) High dose effect (hook effect)
No hook effect was observed up to 2 mg/ml thanks to the proprietary VEDALAB method.
e) Cross-reactivity:
The test showed no cross-reactions with bovine, porcine, rabbit, horse and sheep hemoglobin.
e) Reproducibility:
When two commercial samples were tested with occult blood concentrations of 3.35 and 26.67 ng/ml in 25 replicates, the coefficient of variation of the results was 8.5% and 11.4%, respectively.
g) Diagnostic significance
As discussed below (see Limitations of the Method), there are many reasons for the presence of blood in feces, and the doctor should confirm the results of this test with other clinical methods, such as colonoscopy.
When testing 54 fecal samples, it was determined that results below 100 ng/ml should be interpreted as negative, from 100 to 200 ng/ml as borderline and above 200 ng/ml as positive. However, if other symptoms are present, additional examination is necessary, even if the detected concentration is below 100 ng/ml.
Limitations of the method
1. The test is designed to quantify human blood (hemoglobin) in feces.
2. Blood in the stool can be caused by several reasons other than bowel cancer, such as hemorrhoids, blood in the urine, or stomach irritation. Bleeding from the upper digestive tract (eg, in the case of gastric or duodenal ulcers) may not be consistently detected due to the digestion of proteins and the difficulty of antibody recognition of the hemoglobin antigen after proteolysis.
3. Not all intestinal bleeding can be caused by precancerous or cancerous polyps.
4. As with any diagnostic procedure, the physician must confirm the findings using this test with other clinical methods, such as a barium enema, sigmoidoscopy, or colonoscopy.
5. Negative results do not exclude bleeding, since bleeding may not be constant.
6. Colorectal polyps at a very early stage of the disease may not bleed. For this reason, to be on the safe side, it is recommended to periodically (once a year) check people over 45 years of age.
7. The test is intended only for reading on the “Easy Reader” device. The test is not intended to be read visually.
8. If the reading time (10 minutes) is not observed, false results may be observed.
9. As is observed in other methods of analysis, there is some variability in the measurement results. Therefore, for clinical data, it is recommended to enter a coefficient of variation of +/- 25% relative to the result obtained.
- I. STAGE. COLLECTION OF FECAL SPECIMENS AND HANDLING RULES
- II. STAGE. DIRECT TESTING PROCEDURE
I. STAGE COLLECTION OF FECAL SAMPLES AND RULES FOR THEIR HANDLING
Collection of the stool sample is done using the Stool Collection Paper included in the test kit, or the stool can be collected in a clean, dry container. Instructions for using stool collection paper are included in the kit. The paper is straightened out, the protective layer of self-adhesive tape on the sides is removed and glued to the walls of the toilet, then defecation is performed on the paper to collect stool samples.
If you are unsure about performing the test yourself, you can collect stool in a container and store stool samples in the refrigerator (2-8 °C) for no more than 11 days or at room temperature (no higher than 25 °C) for no more than 5 days. You can perform testing with your doctor directly during your consultation.
II. STAGE. THE TESTING PROCEDURE DIRECTLY.
1. The test cassette and tube containing the stool sample must be kept at room temperature (20–30°C) for at least 10 minutes before testing.
2. Gently shake the tube in the picture (2) for collecting stool, unscrew the top blue cap, take it out along with the applicator stick and use it to take stool samples from those different areas (3). Then put the applicator stick back into the test tube, screw it tightly, and thoroughly mix the contents of the test tube by shaking it several times. Stool samples should be dissolved in saline solution (4).
RICE. 1
3. Remove the foil test cassette immediately before testing. Write the patient's last name and initials on the test cassette.
RICE. 2
4. Open the white cap of the stool sample collection tube RICE. 2.1. To avoid splashing of the solution, use a piece of napkin. Holding the tube upright and pressing the tube with your fingers, add three drops of the solution into both round sample windows (S) of the test cassette.
III. STAGE. EVALUATION OF TEST RESULTS
FIG.3
5. After 5 – 15 minutes, you can visually evaluate the test results. The test plate contains two test zones - Hb - for determining free hemoglobin and Hb/Hp - for determining hemoglobin / haptoglobin complexes (FIG. 4). On the test plate on one side and the other, if the test is performed correctly, pale pink lines should appear in the “C” zone ( FIG.3, FIG.4), if the lines do not appear, it means that the test was performed incorrectly and the test is invalid. If the testing is performed correctly, then we then evaluate the color changes in the “T” zone.
If there is no color change in the “T” zone, then testing is considered negative, i.e. No occult blood was detected in the stool. In this case, to obtain more reliable results, we advise you to undergo re-testing after 3 days. And, in the future, perform a stool test for occult blood once a year. We also advise you to discuss the test results with your doctor. ( FIG.3)
If color changes occur in the “T” zone, in any of the test zones, then the test results are considered positive, i.e. occult blood was detected in the stool. In this case, you need to contact a specialist - a proctologist or gastroenterologist; most likely, you will need an endoscopic examination of the colon ( FIGURE 3, 5, 6).
(FIG.5) Evaluation of the test result for stool occult blood test ColonView Hb and Hb/Hp.
6.1 6.2 6.3 - 6.4
(FIG.6) Interpretation of test results.
6.1 Positive
6.2 Negative
6.3 - 6.4 Invalid
SENSITIVITY AND SPECIFICITY OF THE ColonView Hb and Hb/Hp TEST
When used three times, the sensitivity of the test reaches 100%
Test sensitivity –the accuracy of the test in patients with existing colon pathology, i.e. Carrying out the test three times gives almost 100% detection of pathology. (when the test is performed twice, the sensitivity is 89% (i.e., in 89 out of 100 patients with pathology, the test will be positive and only 11% will be false negative). Studies have shown that the sensitivity of the test for colon cancer reaches 97%. For large colon polyps intestines – 95%.
Specificity of the test -This is the proportion of those who test negative among all people who do not have the disease (condition). This is a measure of the likelihood that a test will correctly identify people who do not have the disease. In the clinic, a test with high specificity is useful to include a diagnosis in the event of a positive result. The specificity of the test reaches 96%.
