The stool occult blood test (FOBT) is a widely used screening tool for detecting hidden blood in stool, which can be an indicator of colorectal cancer or other gastrointestinal disorders. The accuracy of the FOBT is a critical factor in its effectiveness as a screening tool. In this article, we will delve into the accuracy of the FOBT, its reliability, and the factors that can influence its results.
What is the Stool Occult Blood Test?
The FOBT is a non-invasive test that detects the presence of occult blood in stool. Occult blood refers to blood that is not visible to the naked eye. The test involves collecting a stool sample, which is then tested for the presence of hemoglobin or other blood components. There are two main types of FOBT: the guaiac-based test and the immunochemical test (FIT).
Guaiac-Based Test
The guaiac-based test, also known as the gFOBT, uses a chemical called guaiac to detect the presence of hemoglobin in stool. The test involves collecting a stool sample, which is then applied to a test card or strip. The guaiac reacts with the hemoglobin to produce a blue color, indicating the presence of blood. However, this test can be affected by certain foods, such as red meat, horseradish, and turnips, which can cause false-positive results.
Immunochemical Test (FIT)
The FIT is a more sensitive and specific test than the gFOBT. It uses antibodies to detect the presence of human hemoglobin in stool. The FIT is less affected by dietary factors and is more accurate than the gFOBT. However, it is also more expensive.
Accuracy of the Stool Occult Blood Test
The accuracy of the FOBT depends on several factors, including the type of test used, the quality of the stool sample, and the presence of other medical conditions. Studies have shown that the FIT is more accurate than the gFOBT, with a sensitivity of 79-92% and a specificity of 90-95%. The gFOBT has a sensitivity of 50-70% and a specificity of 90-95%.
Reliability of Results
The reliability of the FOBT results depends on several factors, including the quality of the stool sample, the testing methodology, and the interpretation of the results. False-positive results can occur due to dietary factors, certain medications, or other medical conditions. False-negative results can occur if the stool sample is not collected or stored properly.
Factors That Can Influence Results
Several factors can influence the results of the FOBT, including:
- Diet: Certain foods, such as red meat, horseradish, and turnips, can cause false-positive results.
- Medications: Certain medications, such as aspirin and non-steroidal anti-inflammatory drugs (NSAIDs), can cause false-positive results.
- Medical conditions: Certain medical conditions, such as gastrointestinal bleeding, can cause false-positive results.
- Stool sample quality: The quality of the stool sample can affect the accuracy of the results.
- Testing methodology: The testing methodology can affect the accuracy of the results.
Improving Accuracy and Reliability
To improve the accuracy and reliability of the FOBT, several steps can be taken, including:
- Using the FIT: The FIT is more accurate and specific than the gFOBT.
- Following dietary restrictions: Avoiding certain foods and medications can reduce the risk of false-positive results.
- Collecting and storing stool samples properly: Proper collection and storage of stool samples can improve the accuracy of the results.
- Using quality testing methodologies: Using quality testing methodologies can improve the accuracy of the results.
What is the difference between the guaiac-based test and the immunochemical test (FIT)?
+The guaiac-based test uses a chemical called guaiac to detect the presence of hemoglobin in stool, while the FIT uses antibodies to detect the presence of human hemoglobin in stool. The FIT is more sensitive and specific than the guaiac-based test.
What can cause false-positive results in the FOBT?
+Certain foods, such as red meat, horseradish, and turnips, can cause false-positive results. Certain medications, such as aspirin and NSAIDs, can also cause false-positive results.
How can I improve the accuracy and reliability of the FOBT?
+To improve the accuracy and reliability of the FOBT, use the FIT, follow dietary restrictions, collect and store stool samples properly, and use quality testing methodologies.
In conclusion, the stool occult blood test is a widely used screening tool for detecting hidden blood in stool. While it is not 100% accurate, it can be a useful tool for detecting colorectal cancer and other gastrointestinal disorders. By understanding the factors that can influence the results and taking steps to improve accuracy and reliability, individuals can make informed decisions about their health.
