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Test Code FATF Fat, Feces

Reporting Name

Fat, F

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.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Fecal


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.


Specimen Minimum Volume

See Specimen Required

Specimen Stability Information

Specimen Type Temperature Time Special Container
Fecal Frozen (preferred) 180 days
  Refrigerated  180 days

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

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

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

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 Name

Nuclear Magnetic Resonance (NMR) Spectroscopy

Forms

If not ordering electronically, complete, print, and send Gastroenterology and Hepatology Test Request (T728) with the specimen

Day(s) Performed

Monday through Saturday

Report Available

1 to 3 days