Fecal globin is a protein component of hemoglobin, found within red blood cells. Its presence in stool indicates hidden bleeding within the digestive tract, often detected using the Fecal Immunochemical Test (FIT).
Understanding Fecal Globin
Globin is a protein that forms part of hemoglobin, the molecule responsible for carrying oxygen in red blood cells. When red blood cells enter the digestive system due to bleeding, globin can be present in the stool. Its detection serves as a specific indicator of blood loss within the gastrointestinal tract.
The significance of globin in stool lies in its origin from human red blood cells, which distinguishes it from blood that might be present in food. Unlike hemoglobin from the upper digestive tract, which is largely broken down by digestive enzymes, globin from the lower intestines remains intact. Therefore, its presence in feces points specifically to bleeding occurring in the colon or rectum.
The Purpose of Fecal Globin Testing
Healthcare providers use fecal globin testing primarily to screen for colorectal cancer, a condition that often causes hidden blood loss from precancerous polyps or early-stage tumors. This screening plays a role in early detection, allowing for timely intervention before symptoms become apparent. It offers a simple, non-invasive screening alternative.
Beyond colorectal cancer, fecal globin testing helps identify bleeding associated with various other gastrointestinal issues. These include diverticulitis, inflammatory bowel diseases like ulcerative colitis, polyps, or ulcers within the digestive lining.
How Fecal Globin is Detected
Fecal globin is detected using the Fecal Immunochemical Test (FIT). This test utilizes specific antibodies designed to bind exclusively to human hemoglobin, ensuring results are not influenced by dietary factors like red meat consumption.
The collection process is straightforward, involving a small stool sample collected at home, often with a special brush or stick into a provided container. The sample is then securely packaged for mailing to a laboratory for analysis. Because the FIT specifically targets human globin, no special dietary or medication restrictions are required before taking the test.
What Test Results Indicate
A positive fecal globin test result means blood was detected in the stool sample. This indicates bleeding somewhere in the lower digestive tract and suggests the need for further medical evaluation. It does not confirm a diagnosis of colorectal cancer, as many non-cancerous conditions can also cause blood in the stool. Common non-cancerous causes include hemorrhoids, anal fissures, diverticulosis, or inflammatory bowel diseases.
If a test is positive, healthcare providers recommend a follow-up colonoscopy to identify the source of the bleeding. This procedure allows for a direct visual examination of the colon and rectum, enabling the detection and removal of polyps or suspicious tissues. Delays in undergoing a colonoscopy after a positive FIT result can increase the risk of an advanced cancer diagnosis.
Conversely, a negative fecal globin test indicates no blood was detected in the sample. While this is considered a normal result, it does not completely rule out the presence of polyps or cancer, as these conditions may not bleed continuously. Regular, repeated screening with FIT is recommended to account for intermittent bleeding patterns.