anyone ever had or know anything about the "fecal fat test" why must they use this?

DS had one in the hospital at about 2-3 weeks of age. Dietician had inisted, but his doctor said it was kind of silly because they already KNEW he had CF and NEEDED to have enzymes to digest his food. I think based on his comments that the fecal fat test is used to determine pancreatic insufficiency and whether or not enzymes are required. I believe that most cfers do require enzymes.