Under the Affordable Care Act, insured patients pay nothing for a list of preventive services, including screening colonoscopies, screening mammograms, cholesterol tests and the annual physical. The same test, ordered because of a symptom, a finding, or a personal history, is diagnostic, and it is billed against your deductible like anything else. The procedure is identical. The code is different. The bill can differ by thousands of dollars.
What makes a service screening
A screening is done on a person with no symptoms, at the interval a guideline recommends, to look for disease early. A diagnostic service is done because there is a reason: a symptom, an abnormal earlier test, a personal history of the disease, or a follow-up interval shorter than the guideline. The order, the code and the diagnosis attached to the claim decide which it is, and the clinician sets them.
Colonoscopy
- Screening colonoscopy (usually coded with the HCPCS code G0121 or 45378 with a screening diagnosis): every 10 years from age 45 for average-risk adults. Free with insurance.
- If a polyp is found and removed during a screening, federal guidance says it remains a screening and must still be covered without cost-sharing under ACA plans. Medicare treats it slightly differently and may charge coinsurance. Billing errors here are common; if you are charged, appeal.
- Diagnostic colonoscopy (45378, 45380, 45385 with a symptom diagnosis): for symptoms, a positive stool test, or surveillance after prior polyps. Billed against your deductible. A positive at-home stool test converting the follow-up colonoscopy to "diagnostic" was a known loophole; from 2023 federal guidance requires the follow-up to be covered as screening too, but not every plan complies.
Mammogram
- Screening mammogram (77067): yearly or every two years from 40, no symptoms. Free with insurance.
- Diagnostic mammogram (77065, 77066): a lump, pain, discharge, or a call-back after a screening found something. Billed. Nearly one in ten screening mammograms leads to a call-back, and the diagnostic follow-up is where the bill arrives. Some states now require insurers to cover diagnostic breast imaging at no cost; most do not yet.
Laboratory tests and physicals
A lipid panel at an annual physical is preventive; the same test ordered to monitor a statin is diagnostic. The annual physical itself (99385 to 99397) is free, but if you raise a new problem during it, many practices bill a separate problem-focused visit (99213 or 99214) on top, and that one is not free. It is legal, and it is one of the most common complaints about preventive visits.
How to protect yourself
- Before the appointment, ask: "Will this be billed as screening or diagnostic, and with what diagnosis code?" The answer determines your cost.
- If you are asymptomatic and due for a screening, say so, and make sure the order says screening.
- After the service, check the EOB. If a screening was billed as diagnostic, ask the practice to correct the claim; if a polyp removal during a screening was charged, cite the federal guidance and appeal to the insurer.
- If you are self-pay, the distinction does not change the hospital's cash price, but the follow-up codes (biopsy, polyp removal) do. Ask for the price of each.
Why it matters for price comparison
The price files list diagnostic codes, because that is what hospitals bill. A published cash price for 45378 is what a self-pay patient pays for the procedure regardless of why it was ordered. For insured patients, the same number is irrelevant if the service is a covered screening, and very relevant if it is not. Know which side of the line you are on before you go.