The presence of lactoferrin in a stool sample is a significant finding used by healthcare providers to investigate various digestive symptoms, such as chronic diarrhea, abdominal pain, and unexplained weight loss. The fecal lactoferrin test is a non-invasive screening tool designed to determine if inflammation is occurring within the gastrointestinal (GI) tract. A positive result strongly indicates that the lining of the intestines is actively inflamed, suggesting that the symptoms are likely due to an underlying inflammatory disease process. This test helps differentiate between conditions characterized by true inflammation and non-inflammatory or functional disorders.
What Lactoferrin Is and Its Role in Inflammation
Lactoferrin is a protein naturally present in several bodily fluids, including tears, saliva, and human milk, where it aids immunity and iron binding. This protein is stored in high concentrations inside neutrophils, a type of white blood cell. Neutrophils are the immune system’s first responders, rapidly migrating to sites of tissue injury or infection to initiate a defense response.
When the gut lining becomes inflamed, large numbers of neutrophils are recruited from the bloodstream into the intestinal tissue. As these immune cells fight inflammation, they break down, releasing lactoferrin directly into the intestinal lumen. The released lactoferrin passes through the GI tract and is excreted in the stool. Detecting elevated levels of lactoferrin in a fecal sample thus serves as a direct marker for active neutrophils and inflammation within the intestinal wall.
Interpreting Fecal Lactoferrin Test Results
Fecal lactoferrin test results are typically reported in micrograms of lactoferrin per gram of stool (\(\mu\)g/g), and the measurement helps assess the severity or presence of mucosal inflammation. A result below a certain cutoff, often cited as less than 7.25 \(\mu\)g/g, generally indicates that significant intestinal inflammation is absent. This negative result suggests that a patient’s symptoms may be due to a functional disorder, such as Irritable Bowel Syndrome (IBS), which does not involve inflammation.
Conversely, a result exceeding this cutoff is considered positive and confirms the presence of active inflammation in the GI tract. The higher the measured level, the greater the number of neutrophils present and the more severe the inflammation is likely to be. As a screening tool, lactoferrin helps physicians determine the necessity for more involved diagnostic procedures, potentially reducing the number of patients requiring an immediate, invasive procedure like a colonoscopy.
Specific Conditions That Elevate Stool Lactoferrin
The presence of elevated lactoferrin confirms gut inflammation but does not specify the underlying cause, which can be grouped into chronic or acute conditions. Persistently high levels are often associated with chronic Inflammatory Bowel Disease (IBD). This category includes Crohn’s Disease and Ulcerative Colitis, where the immune system mistakenly attacks the GI tract, leading to long-term inflammation and damage.
The test is useful for distinguishing IBD from non-inflammatory conditions that share similar symptoms, such as IBS. However, temporary or acute conditions can also cause a spike in lactoferrin levels. Acute bacterial gastroenteritis, often caused by pathogens like Clostridium difficile or Salmonella, results in a powerful inflammatory response that recruits neutrophils.
Other causes of elevated lactoferrin include severe infectious diarrhea and enteritis linked to certain medications. Nonsteroidal anti-inflammatory drugs (NSAIDs) can irritate the bowel lining, causing inflammation and a subsequent rise in the protein marker. Since the test cannot differentiate between chronic IBD and these temporary inflammatory events, a physician must consider the patient’s entire clinical picture, including the duration of symptoms and other test results, to determine the exact diagnosis.
Next Steps After Receiving a Positive Result
A positive fecal lactoferrin result requires a follow-up consultation with a healthcare provider, typically a gastroenterologist, for further evaluation. The immediate next steps involve determining the specific cause of the inflammation indicated by the marker. This process usually begins by ruling out infectious etiologies, such as bacterial infections, through additional stool panel testing.
Once acute infection is excluded, a physician may recommend an endoscopic evaluation, such as a colonoscopy, to visually inspect the intestinal lining. This procedure allows for the collection of tissue samples, known as biopsies, which are necessary to establish a definitive diagnosis, particularly for chronic conditions like IBD. The lactoferrin test serves as a valuable initial screen, guiding the need for these more comprehensive diagnostic measures.