4
Diagnosing Fat Malabsorption
Table 3. Tests for Fat Malabsorption
Test Procedure
Qualitative Fecal Fat
("spot or random check")
Single stool specimen is assessed for fat content.
Quantitative Fecal Fat
Fat malabsorption
confirmed if there is >7 g
stool fat on 100 g fat/day
diet or >7% of fat intake
of the recorded diet
Complete a diet record of all oral and enteral nutrition
beginning the day before the stool collection and continue
throughout the testing period to assess grams of fat ingested
in order to compare with that lost in stool.
Collect and keep in a cool place all stool over a 72-hour
period for assessment of fat content. Shorter 24- and
48-hour studies are less ideal but may still be useful if fat
malabsorption is documented and may be more easily
performed in the inpatient setting for patients who cannot
stay 3 days.
Fecal Elastase (FE-1)
Mild to moderate EPI =
<200 μg/g
Severe EPI = <100 μg/g
Elastase is secreted by pancreas and is stable in the GI tract.
If present, it will not be degraded so its presence in the stool
reflects general pancreas enzyme secretion.
Measurement is from a single stool sample using an enzyme-
linked immunosorbent assay (ELISA) and does NOT
require dietary fat intake.
Bile Salt Deficiency There is limited testing specific to bile salt deficiency. Most
commonly, this is a clinical diagnosis in the context of fat
malabsorption and related diagnoses (see Table 2).
KEY POINT: Suboptimal studies can sometimes be interpreted. A high % of fat lost in
the stool could still be considered positive if <50g of fat consumed if there is an accurate
record of grams of fat ingested.
• While malabsorption may contribute to diarrhea, inflammatory, and
secretory causes of diarrhea should also be considered and excluded. If there
is a question of secretory or inflammatory diarrhea, an NPO trial is a valuable
test. If diarrhea persists in a patient who is NPO, further evaluation should
be dedicated to secretory and inflammatory causes of diarrhea.
