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Fecal Fat Qualitative

The qualitative fecal fat test is a screening test for steatorrhea.Steatorrhea is the clinical syndrome caused by malabsorption of dietary fat. Causes of steatorrhea include Zollinger-Ellison syndrome, increased duodenal acid, abnormal bile output, pancreatic insufficiency, intestinal mucosal impairment, Whipple's disease, and various forms of enteritis, celiac disease and sprue.

Small fat droplets are observed in stools from healthy persons because there is always a small amount of fat from endogenous sources such as exfoliated epithelial cells. In patients with steatorrhea, the size and number of fat droplets are increased. The severity of steatorrhea can be graded only in broad terms because this is a qualitative test. Abnormal results should be confirmed with a timed-collection specimen and quantitative analysis.

False positive results may follow ingestion of nonabsorbable fat such as castor or mineral oil. False negative results are associated with inadequate intake of dietary fat or dilution of intestinal contents with barium.

Olestra is a fat substitute that consists of 6 to 8 fatty acids esterified to a sucrose molecule. It is not hydrolyzed by lipolytic enzymes in the GI tract and may produce symptoms of malabsorption. A recent study investigated the effect of olestra consumption on fecal fat excretion (Ann Int Med 2000; 132:279-82). One ounce of olestra potato chips contains 8 g of olestra and can persist in stool for up to seven days after ingestion. The results of this study indicate that false positive fecal fat tests may occur in individuals consuming olestra chips, which could lead to unnecessary additional testing for malabsorption.

Reference value is <20% fat.

Specimen requirement is 5 gm of frozen random stool collected in a container.

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