25443 Fat, Feces (FATF)

​Fat, Feces, Random, Fecal Fat, Fecal Fat, Quantitative, Fecal Fat, Random, Lipids, Stool, Stool, Fat, Coefficient of Fat Absorption (CFA), Fecal Fat, Timed, FATF

ST FATFSO

Diagnosing fat malabsorption due to pancreatic or intestinal disorders

Monitoring effectiveness of enzyme supplementation in certain malabsorption disorders

This test is not useful for differentiating among pancreatic diseases.

Patient Preparation:

1. For 3 days prior to and during the collection period:

a. Patient should be on a fat-controlled diet (100-150 g fat per day).

b. No laxatives (particularly mineral oil and castor oil).

c. No synthetic fat substitutes (eg, Olestra) or fat-blocking nutritional supplements.

2. The use of diaper rash ointments will falsely elevate test results. Discontinue use during collection period.

3. Barium interferes with test procedure; a waiting period of 48 hours before stool collection analysis is recommended.

Must use Mayo collection containers (supply T291) provided by Marshfield Labs.

Length of collection period is required.

Additional Information:

1. Patient can store sample at refrigerate temperature during collection period.

2. A separate order and collection should take place if stool bicarbonate, calcium, chloride, magnesium, osmolality, pH, potassium, sodium, or any microbiology testing is desired.

Preservative, media, or charcoal

​Proper patient preparation is critical. Failure to adhere to a fat-controlled diet or to exclude other oils or oil substitutes from the diet may make interpretation difficult.

Barium interferes with test procedure; a waiting period of 48 hours before fecal collection is recommended.

The use of charcoal as a marker is not recommended. If charcoal is used, please notify the laboratory.

​Total fecal lipids include glycerides, phospholipids, glycolipids, soaps, sterols, cholesteryl esters, and sphingolipids. Excess fecal fat in feces, (steatorrhea) is indicative of malabsorption disorders, such as pancreatic insufficiency or Whipple disease. Therefore, measurement of the fecal fats can be useful in establishing a diagnosis of such pancreatic diseases as cystic fibrosis, chronic pancreatitis, neoplasia, or stone obstruction, and such intestinal diseases as Whipple disease, regional enteritis, tuberculous enteritis, gluten-induced enteropathy (also called celiac disease or sprue), and the atrophy of malnutrition. 

Distinguishing free fatty acids from neutral fats, once thought to be helpful in the differential diagnosis of pancreatic disease, has fallen out of favor. Note that the composition of fats in the feces, normally predominately free fatty acids, can change significantly to predominately neutral fatty acids when the patient is on orlistat. This test does not distinguish between free and neutral fatty acids.

​Excretion of >7 grams fat/24 hours, when on a diet of 100 to 150 g of fat, is suggestive of a malabsorption defect.

Abnormal results from a random specimen should be confirmed by submission of a timed collection.

Test values for timed fecal fat collections will be reported in terms of g/24 hours; the duration of the collection may be 24, 48, 72, or 96 hours.  Test values for random fecal fat collections will be reported in terms of percent fat.

Coefficient of Fat Absorption (CFA) can be calculated as follows:

            (grams fat consumed – grams of fat excreted) x 100

   CFA = --------------------------------------------------------------

                        grams of fat consumed