Abnormal Fecal Fat Results

My four year old has Asperger's, joint pain, abdominal pain, and mild asthma symptoms.  He has already been seen by a rheumatologist who saw no sign of arthitis and suggested he be seen by a gastroenterologist.  We took him to the GI in July.  He ordered two fecal fat labs.  Both came back abnormal.  He is now testing for cystic fibrosis and celiac disease.  I am a carrier of the cystic fibrosis mutation delta F508.  My husband's carrier screen came back negative five years ago.  My son is on a GFCF diet except for once in awhile when we go out to eat.  He hadn't had gluten for quite some time before the fecal fat tests were done.
He doesn't really have diarrhea or fever.
Are we wasting our time with the CF genetics test and the celiac labs?  What else could cause these abnormal results given that he doesn't have diarrhea or fever?