How often are 72-hour fecal fat studies ordered?

From the Guidelines

Three-day fecal fat studies are rarely ordered in modern clinical practice, as stated in the most recent guidelines 1. These tests are typically reserved for cases where malabsorption is strongly suspected but cannot be confirmed through more common, less cumbersome diagnostic methods. The test is usually ordered only after initial evaluations with blood tests, imaging studies, and specific disease markers have been inconclusive. When ordered, the protocol requires patients to consume a high-fat diet (typically 100g of fat daily) for 3-5 days, with stool collection occurring during the final 72 hours. Some key points to consider when ordering a 72-hour fecal fat study include:

• The test's practical challenges, including patient compliance with diet restrictions, complete stool collection, and laboratory handling difficulties, have further limited its routine use 1.
• Most gastroenterologists now prefer targeted testing based on specific clinical suspicions rather than this general screening approach 1.
• The development of more specific diagnostic tools for conditions like celiac disease, pancreatic insufficiency, and inflammatory bowel diseases has reduced the need for three-day fecal fat studies 1.
• Fecal elastase testing is often preferred over fecal fat testing due to its ease of use and availability 1. In general, the use of 72-hour fecal fat studies should be discouraged in favor of more targeted and less burdensome diagnostic approaches 1.

From the Research

Frequency of 72-hour Fecal Fat Studies

• The frequency of ordering 72-hour fecal fat studies is not directly stated in the provided studies 2, 3, 4, 5, 6.
• However, the studies suggest that 72-hour fecal fat studies are used as a gold standard for diagnosing fat malabsorption 5 and are recommended for determining fecal fat output 2.
• Some studies propose alternative methods for screening malabsorption, such as near-infrared analysis of spot samples of feces 2 or a novel assay using fecal lauric/behenic acid 5, which may reduce the need for 72-hour fecal fat studies.
• The use of 3-day stool collection is considered necessary for accurate diagnosis of malabsorption in some cases 3, but other studies suggest that 1-day or 24-hour stool collection may be sufficient for screening purposes 4, 6.

Alternative Methods and Diagnostic Efficiency

• Near-infrared analysis of stool samples has been proposed as a useful test for diagnosing fat malabsorption, with a diagnostic efficiency of 72% for pancreatic steatorrhea and 61% for nonpancreatic steatorrhea 2.
• The behenate test, a novel assay using fecal lauric/behenic acid, has been compared to the gold standard 72-hour fat balance study, but the correlation between the two tests was not robust enough to justify replacement of the gold standard 5.
• Estimating the 3-day faecal fat excretion and fat concentration has been shown to have a diagnostic sensitivity of 90% and can be used to distinguish between malabsorption and maldigestion 6.