They examine cost of claims to determine whether it is a reasonable or necessary, according to diagnosis.

Coders assign standardized ICD and CPT codes to patient records and procedures - they do not evaluate whether the cost of a claim is reasonable or medically necessary.

Billers are responsible for submitting claims to insurance payers and pursuing reimbursement - their role is administrative and financial, not evaluative of medical necessity or cost appropriateness.

A Health Insurance Specialist evaluates submitted medical claims by comparing the cost of services against the patient's diagnosis to determine whether the care was medically necessary and whether charges fall within reasonable and customary rates. This role requires knowledge of both clinical guidelines and insurance coverage criteria to make accurate coverage determinations.