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HelpMayo Test ID FATF Fat, Feces
Necessary Information
Length of collection period is required.
Specimen Required
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.
Supplies: Stool Containers - 24, 48, 72 Hour Kit (T291)
Container/Tube: Stool container complies with shipping requirements, do not use other containers.
Specimen Volume:
Preferred: Entire 48-hour or 72-hour collection
Acceptable: Entire 24-hour or a minimum of 5 g from a random collection
Collection Instructions:
1. All containers must be sent together.
2. The entire collection must contain at least 5 g of feces.
3. For a random collection, a minimum of 5 g (do not send entire collection) is required.
4. The number of containers sent should be indicated on the labels (1 of 4, for example).
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.
Useful For
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.
Method Name
Nuclear Magnetic Resonance (NMR) Spectroscopy
Reporting Name
Fat, FSpecimen Type
FecalSpecimen Minimum Volume
See Specimen Required
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Fecal | Frozen (preferred) | 180 days | |
| Refrigerated | 180 days |
Reject Due To
| Preservative, media, or charcoal | Reject |
Clinical Information
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.
Reference Values
TIMED COLLECTION
≥18 years: 2-7 g fat/24 h
Reference values have not been established for patients who are younger than 18 years of age.
RANDOM COLLECTION
All ages: 0-19% fat
Interpretation
Excretion of more than 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
Cautions
Proper patient preparation is critical (see Specimen Required). 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.
Clinical Reference
1. Hart PA, Conwell DL. Diagnosis of exocrine pancreatic insufficiency. Curr Treat Options Gastroenterol. 2015;13(3):347-353. doi:10.1007/s11938-015-0057-8
2. Sherwood RA, Walsham NE: Evaluation of fat absorption. In: Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023:764
3. Erchinger F, Engjom T, Jurmy P, Tjora E, Gilja OH, Dimcevski G. Fecal fat analyses in chronic pancreatitis importance of fat ingestion before stool collection. PLoS One. 2017;12(1):e0169993. Published 2017 Jan 17. doi:10.1371/journal.pone.0169993
Method Description
After the well-homogenized stool sample is weighed and dried, it is rolled in Teflon and placed in a nuclear magnetic resonance spectrometer (NMR). The NMR determines the percent of fat in the sample. The percent is then converted to grams fat/24 hours excretion or percent fat of random sample.(Korpi-Steiner NL, Ward JN, Kumar V, McConnell JP. Comparative analysis of fecal fat quantitation via nuclear magnetic resonance spectroscopy [1H NMR] and gravimetry. Clin Chim Acta. 2009;400[1-2]:33-36)
Specimen Retention Time
7 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82710
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| FATF | Fat, F | 16142-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| STWT | Total Weight | 30078-0 |
| DUR2 | Duration | 13363-7 |
| PFAT | Percent Fat | 35745-9 |
| TFAT | Total Fecal Fat/24 Hr | 16142-2 |
Day(s) Performed
Monday through Saturday