<<Disclaimer: Verify this information before applying it to your situation.>>
 
The fecal fat test is a non-specific test to tell how badly (or how
well) your small intestine is functioning.  There will be a lot of fat
in your stool if you have active celiac disease as well as other small
intestine diseases such as giardiasis (an intestinal parasite).
In other words, the Fecal Fat Test will not tell you the underlying
cause of malabsorption, just the degree of it!
It seems to me an unnecessary but harmless test.....