Elevated lipase while fasting, normal when non-fasting

Two years in a row now during my yearly physical my lipase levels were elevated during my fasting blood test (202 in 2009 & 282 this year).  Last year they had me do a CAT scan which revealed nothing so we redid the lipase blood test, but did it non fasting. Same thing this year, except no CAT scan.  In 2009 the non-fasting lipase came back at 29 and this year the non-fasting came back at 31.

What would cause lipase levels to be elevated during a fasting blood test but normal during a non-fasting blood test?