Eosinophil Protein X (EPX) is a water-soluble protein that is found in eosinophils.

EPX levels in stool are a marker of eosinophil activity in the gastrointestinal system. Fecal EPX abnormality is suggestive of food allergy, eosinophil-driven inflammation (caused by parasites). The test has been shown to have higher specificity and positive predictive value for detecting disease activity in inflammatory bowel disease compared to fecal calprotectin.

When you eat fat, a small amount of the fat passes out the body through the colon. Some of the different types of fats in the feces include phospholipids, sterols, sphingolipids, cholesteryl esters, glycolipids, soaps and glycerides.  

A fecal fat test helps your doctor identify pancreatic or intestinal disorders. It can indicate your body isn’t creating enough enzymes or there is malabsorption.

The FIT test on the Gut Zoomer detects microscopic human blood in stool. It is used to identify hidden gastrointestinal bleeding, often before symptoms appear. FIT is specific to bleeding in the lower GI tract, making it useful for identifying issues in the colon or rectum.

A positive FIT may indicate inflammation, polyps, hemorrhoids, ulcers, or—less commonly—colorectal cancer. A negative FIT means no blood was detected but does not completely rule out digestive problems.

If your FIT result is positive, follow up with your healthcare provider. Further evaluation may include stool inflammatory markers, imaging, or colonoscopy, depending on your symptoms and medical history.

Lactoferrin is a glycoprotein released by a type of white blood cell called neutrophil.

Fecal lactoferrin levels are helpful in monitoring disease activity and efficacy of treatment for IBD.

Fecal lactoferrin is a valuable biomarker measured in GI tests to assess inflammation in the gastrointestinal tract. It is a protein released by neutrophils, a type of white blood cell, during inflammation, making its presence in stool indicative of inflammatory processes within the gut. Elevated levels of fecal lactoferrin are often associated with conditions such as inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, and can help differentiate these from non-inflammatory conditions like irritable bowel syndrome (IBS).

The fecal occult blood test (=FOBT) looks for blood in your feces. “Occult” (=hidden) means that the blood amount is so small that it cannot be seen with the naked eye. The bleeding does not change the color of the stool or result in visible bright red blood. Therefore, the blood is found only by testing the stool for blood in the laboratory.

Fecal occult blood testing (FOBT) checks stool samples for hidden (occult) blood loss from the mouth to the colon.

The fecal occult blood test (=FOBT) looks for blood in your feces. “Occult” (=hidden) means that the blood amount is so small that it cannot be seen with the naked eye. The bleeding does not change the color of the stool or result in visible bright red blood. Therefore, the blood is found only by testing the stool for blood in the laboratory.

Blood in the stool means there is likely some kind of bleeding in the digestive tract. It can be a sign of a problem in your digestive system, such as a growth, or polyp, or cancer in the colon or rectum.

– This test is a screening that may help find colorectal cancer early, when treatment is most effective.

– Occult blood means that you can’t see it with the naked eye.

– Identifies microscopic amounts of blood in the stool

A fecal pH test is one where a specimen of feces is tested for acidity in order to diagnose a medical condition.

- Human feces is normally acidic.

- The average pH for a healthy person is a pH of 6.6.

Fecal pH is dependent in part on fermentation of sugars. Colonic fermentation of normal amounts of carbohydrate sugars and production of fatty acids accounts for the normally slightly acidic pH.

Fecal Secretory IgA is a marker of gut secretory immunity and barrier function.

Fecal zonulin is a biomarker of intestinal permeability, often referred to as “leaky gut.” Zonulin is a protein that regulates the tight junctions between intestinal cells. When zonulin levels rise, these junctions loosen, allowing larger molecules — such as food proteins, toxins, or microbes — to pass into the bloodstream, which can trigger inflammation and immune responses.

Measuring zonulin in stool is considered more gut-specific than serum testing, since blood levels can also be influenced by production in other organs like the liver, heart, and brain. Elevated fecal zonulin has been associated with conditions such as celiac disease, non-celiac gluten sensitivity, Crohn’s disease, ulcerative colitis, IBS-D, metabolic syndrome, obesity, type 1 diabetes, and autoimmune disorders. Lifestyle factors like smoking, stress, and processed food intake can also affect zonulin release.

Fecal zonulin is most informative when used alongside other stool markers (such as calprotectin, secretory IgA, or anti-gliadin IgA) to help assess gut barrier integrity and distinguish between inflammatory bowel disease and other gastrointestinal disorders.

Protein that stores iron. Red blood cells need iron to carry oxygen around the body such as the liver, bone marrow, and muscles. An indirect marker of the total amount of iron stored in the body; hence, serum ferritin is used as a diagnostic test for iron- deficiency anemia.

Ferritin is a protein that serves as a storehouse for iron in the body. When iron supplies dwindle, ferritin releases some into the blood. Therefore, a blood ferritin test is an indication of how much iron is stored in the body. Iron is used primarily by red blood cells to carry oxygen to other cells, and as such Ferritin is vital to blood health. 

Ferritin is a protein that serves as a storehouse for iron in the body.

When iron supplies dwindle, ferritin releases some into the blood. Therefore, a blood ferritin test is an indication of how much iron is stored in the body. Iron is used primarily by red blood cells to carry oxygen to other cells, and as such Ferritin is vital to blood health. 

What is FGF-23?

FGF-23, or fibroblast growth factor 23, is a hormone-like protein that plays a critical role in phosphate and vitamin D metabolism. It is primarily produced by bone cells (osteocytes and osteoblasts) and acts mainly on the kidneys to regulate:

• Phosphate excretion in urine

• Vitamin D activation

• Calcium-phosphate balance

FGF-23 is part of a feedback system that helps maintain normal blood phosphate levels. When phosphate levels rise, FGF-23 secretion increases to help eliminate excess phosphate through the urine and reduce vitamin D activation.

The FIB-4 Index, a non-invasive and widely used clinical tool, is instrumental in the assessment of liver fibrosis, particularly in patients with chronic liver diseases such as Hepatitis C and Non-Alcoholic Fatty Liver Disease (NAFLD). This index, calculated using a simple formula that incorporates age, platelet count, and liver enzyme tests (AST and ALT levels), offers a cost-effective and easily accessible means of evaluating liver health.

If your FIB-4 Index result shows an Indeterminate risk for advanced liver fibrosis, it means that your score falls within a range where the risk of significant liver scarring (fibrosis) is uncertain. This does not confirm or rule out advanced liver fibrosis but suggests that further testing may be needed for a more definitive assessment.

Understanding FIB-4 Index

The FIB-4 Index is a non-invasive biomarker used to estimate liver fibrosis risk. It is calculated using age, AST (aspartate aminotransferase), ALT (alanine aminotransferase), and platelet count. The score is typically interpreted with the following cutoffs:

• Low Risk: FIB-4 < 1.3 (unlikely to have advanced fibrosis)
• Indeterminate Risk: FIB-4 between 1.3 and 2.67 (uncertain risk)
• High Risk: FIB-4 > 2.67 (higher likelihood of advanced fibrosis)

What an Indeterminate Result Means

• Your FIB-4 score is neither clearly low nor high, meaning that advanced liver fibrosis cannot be ruled out.
• This result may be due to age, mild liver enzyme abnormalities, or borderline platelet counts.
• It does not necessarily mean you have liver disease, but further evaluation is recommended.

Next Steps

If your FIB-4 result falls in the indeterminate range, your healthcare provider may:

• Order additional tests, such as the FibroScan (elastography), liver biopsy, or more advanced fibrosis markers (e.g., ELF test, APRI score).
• Monitor your liver health over time with repeat FIB-4 testing and blood work.
• Evaluate potential causes of liver injury, including fatty liver disease (NAFLD/NASH), viral hepatitis, alcohol use, metabolic conditions, or medication effects.

Key Takeaway

An indeterminate FIB-4 result means further evaluation is needed to clarify your liver fibrosis status. It does not confirm serious liver disease but suggests that monitoring and possibly additional testing are advisable.

U3-RNP antibodies target the U3 small nucleolar ribonucleoprotein (U3-RNP) complex, which consists of the protein fibrillarin and U3 RNA. These antibodies are found in about 4% to 10% of patients with SSc, and are especially common in African American SSc patients (approximately 30%). U3-RNP antibodies are rarely found in patients with other autoimmune disorders; thus, the presence of these antibodies supports a SSc diagnosis. 

These antibodies occur most often in dcSSc, but they can also occur in lcSSc.

U3-RNP antibodies are associated with multiorgan involvement, including the heart, kidneys, muscle, lungs, and gastrointestinal system. Their presence is an independent risk factor for the development of PAH, and PAH is the most common cause of death in U3-RNP–positive patients. Therefore, their presence indicates a poorer prognosis.

Fibrinogen is a key marker included in the Inflammation and Oxidation Test panel by Boston Heart Diagnostics, primarily due to its critical role in the body's clotting process and its association with inflammation. Essentially, fibrinogen is a blood plasma protein that's converted into fibrin by the action of the enzyme thrombin during blood clot formation. This process is crucial for stopping bleeding and initiating the healing process following an injury. However, elevated levels of fibrinogen can indicate an increased risk of clot formation within the blood vessels, which is a significant concern because it can lead to blockages, thereby increasing the risk of heart attacks and strokes.