What It Is
A stool occult blood test checks for the presence of blood in the stool that isn't visible to the naked eye, which can be an early sign of a problem somewhere along the digestive tract.
What It Checks
The test detects small amounts of blood mixed into a stool sample that wouldn't otherwise be noticeable through simple visual inspection. Depending on the specific type of test used, it may detect blood through a chemical reaction or through detecting a specific protein found in blood.
Why It's Used
A stool occult blood test is commonly used as a screening tool for colorectal health, given that certain conditions affecting the colon can cause small, otherwise unnoticed amounts of bleeding, and is also used to investigate symptoms such as unexplained anemia that might relate to ongoing digestive tract blood loss.
How It's Done
A stool occult blood test requires a small stool sample, which the person typically collects at home using a kit provided by their healthcare provider or laboratory, following the specific collection instructions included. The sample is then returned to a laboratory for testing.
Background
Chemical methods for detecting hidden blood in stool were developed in the late 19th and early 20th centuries, and the test became more widely used as a general screening tool over the following decades. More specific, protein-based versions of the test were developed later in the 20th century, offering improved accuracy compared to earlier chemical-based methods, and stool occult blood testing remains a widely used, accessible screening tool today.