Sounds like the doctor chose an ICD-9 code(diagnosis code) for the cholesterol panel that was considered diagnostic, and not preventative/screening. Therefore your insurance is not paying. Please, don't believe doctors/office staff when they tell you: "You've got insurance, they'll cover them." "Them" being tests, blood work, etc,.
how you can ask them to code it for a re-submission that will cover the cholesterol screening.