What Is Modifier PT?
Modifier PT is a Medicare billing modifier that flags a colorectal cancer screening test that converted to a diagnostic or therapeutic procedure during the same visit, most often a screening colonoscopy where a polyp was found and removed. It is appended to the diagnostic or therapeutic CPT code, not the screening code, and it tells Medicare to waive the deductible and apply the reduced screening coinsurance so the patient is not billed as if the visit were fully diagnostic.
Medicare only. Modifier PT is a Medicare modifier. Commercial and Medicaid plans use modifier 33 for the same screening-conversion scenario, and the two are never interchangeable.
Goes on the therapeutic code. Append PT to the procedure that was actually performed, such as 45385 for a snare polypectomy, not to the screening G-code.
It protects the patient. With PT, Medicare waives the deductible and charges only the phased-down screening coinsurance: 15% in 2026, dropping to 10% for 2027 through 2029 and 0% in 2030.
How Modifier PT Works in 2026
Modifier PT is a small string of characters with an outsized effect on the patient’s bill. A screening colonoscopy that finds a polyp converts to a therapeutic procedure, which happens in roughly 35% to 40% of screenings, and without PT the claim processes as fully diagnostic: full deductible, full coinsurance, and a patient who was promised a free screening opening a surprise bill. With PT, Medicare waives the deductible and applies the reduced screening coinsurance.
The most common issue we see GI practices run into is not understanding that PT goes on the therapeutic code, not the screening code. Append it to the CPT code for the procedure actually performed, such as 45385 for snare polypectomy. Never attach it to the screening G-code (G0105 or G0121). The proposed 2027 Medicare GI payment changes will further reduce endoscopy reimbursement, making correct modifier application even more critical to protecting revenue.
| Modifier | Payer | Use it when | Effect |
| PT | Medicare | Screening colonoscopy converts to diagnostic/therapeutic (polyp removed) | Waives deductible; reduced coinsurance (15% in 2026) |
| 33 | Commercial and Medicaid | Screening service is delivered or converts under a commercial plan | Triggers ACA preventive coverage, typically zero cost-sharing |
| KX | Medicare | Screening colonoscopy follows a positive stool test (Cologuard, FIT) | Marks a complete CRC screening; patient pays nothing |
Which Codes Take Modifier PT?
Modifier PT attaches to the diagnostic or therapeutic procedure performed during a converted screening, not to the screening code. The codes that commonly carry PT include:
1. 45380, colonoscopy with biopsy, when tissue is sampled during a converted screening.
2. 45384, colonoscopy with removal by hot biopsy forceps, when a polyp is removed by hot forceps.
3. 45385, colonoscopy with removal by snare, the most common converted-screening code.
4. 45388, colonoscopy with ablation, when a lesion is destroyed rather than removed.
5. 00811, anesthesia for a lower GI endoscopy that became diagnostic, reported with PT; screening anesthesia uses 00812.
Where Does Modifier PT Go on the Claim?
Append modifier PT to the diagnostic or therapeutic CPT code that was performed, once per affected line, not to the screening G-code and not to lab or pathology services. Sequence the screening diagnosis, Z12.11, first and the finding second. When stacking modifiers, place the payment-affecting modifier before the informational ones.
The anesthesia line has its own rule that trips people up. When a screening colonoscopy stays a screening, the anesthesia code is 00812 with no PT. When it converts, anesthesia is reported with 00811 and modifier PT. Do not append PT to unrelated anesthesia codes such as 00730, 00740, or 00813. Because some of these edits vary by Medicare Administrative Contractor, confirm your MAC’s specific guidance before building the claim, especially for the anesthesia and moderate-sedation lines.
Modifier PT, modifier 33, and KX each protect a different screening scenario, and one wrong or missing character turns a free screening into a patient’s surprise bill and a denied claim. If converted screenings are costing you denials or patient complaints, get matched with a billing partner that codes colorectal screening correctly. Comparing quotes is free, and matches typically come back within 30 minutes.
Why Do Modifier PT Claims Get Denied?
Most modifier PT problems fall into a short, preventable list:
1. Missing PT entirely. The converted screening processes as fully diagnostic, the deductible and full coinsurance apply, and the patient gets a surprise bill. Fix it by appending PT to every therapeutic line on a converted screening.
2. PT on the wrong code. Appending PT to the screening G-code instead of the therapeutic CPT. Fix it by placing PT on the procedure actually performed.
3. Crossed modifiers. Using PT on a commercial claim or modifier 33 on a Medicare colonoscopy. Fix it by matching PT to Medicare and 33 to commercial.
4. Missing KX after a positive stool test. A follow-on Medicare screening colonoscopy without KX returns as unprocessable, which carries no appeal rights. Fix it by appending KX to the screening colonoscopy code.
5. PT on lab or pathology. Applying PT or 33 to a pathology line. Fix it by keeping those modifiers on the procedure only.
6. Diagnosis sequencing error. Listing the finding before the screening code. Fix it by sequencing Z12.11 first so the screening intent is clear.
What Does Miscoding a Converted Screening Actually Cost?
Consider a 68-year-old Medicare patient scheduled for a routine average-risk screening colonoscopy (G0121), expecting to owe nothing. The endoscopist removes a polyp by snare. The correct billing is 45385 with modifier PT. Coded that way, Medicare waives the deductible and the patient owes only the 2026 reduced coinsurance of 15%. Leave PT off, and the exact same claim processes as a standard therapeutic colonoscopy: the full Part B deductible and 20% coinsurance apply, and the patient receives a bill for hundreds of dollars on a screening they were told was free. Nothing about the procedure changed. One modifier is the entire difference between a protected patient and an angry call to your billing office. In our experience matching GI practices with billing partners through Gastroenterology Billing, the practices that struggle most with converted screenings are the ones where the billing team does not have a modifier checklist built into the charge capture workflow.
Medicare Coinsurance Phase-Out
The Consolidated Appropriations Act of 2021 established a gradual reduction of patient cost-sharing on converted screening colonoscopies. Under this schedule, the patient’s coinsurance drops over time until it reaches zero:
| Year | Medicare coinsurance on converted screening | Deductible |
| 2023 to 2026 | 15% | Waived |
| 2027 to 2029 | 10% | Waived |
| 2030 and beyond | 0% | Waived |
Across the billing companies we vet, the practices that set patient expectations correctly at the front desk, telling the patient before the procedure that they may owe up to 15% if a polyp is found and removed, see far fewer billing complaints and write-offs than the ones that promise a free screening without the caveat.
Frequently Asked Questions
You should not lose revenue or a patient’s trust to a missing modifier on a screening that converted. Billing Service Quotes matches gastroenterology practices and endoscopy centers with vetted medical billing companies that handle modifier PT, screening conversions, and the full colonoscopy family correctly, across all 50 states. Comparing quotes is 100% free for providers, with rates starting as low as 2.95% and matches typically returned within 30 minutes.
Is modifier PT only for Medicare?
Yes. Modifier PT is a Medicare modifier for a colorectal screening that converts to diagnostic or therapeutic. Commercial and Medicaid plans use modifier 33 for the same scenario. Medicare does not recognize 33 on colonoscopy codes, so the two cannot be substituted for each other.
Do you put modifier PT on the screening code or the diagnostic code?
The diagnostic or therapeutic code. Append PT to the procedure actually performed, such as 45385 for snare polypectomy. Never attach it to the screening G-code, G0105 or G0121, or to lab and pathology lines. PT belongs on the procedure that converted the screening.
What is the difference between modifier PT and KX for colonoscopy?
PT marks a screening that converted to diagnostic or therapeutic during the visit. KX marks a Medicare screening colonoscopy performed after a positive non-invasive stool test such as Cologuard or FIT. If polyps are removed during that follow-on colonoscopy, the therapeutic code also takes modifier PT.
Does modifier PT waive the patient’s entire cost?
Not entirely, yet. PT waives the Part B deductible, but a reduced coinsurance still applies: 15% in 2026, dropping to 10% for 2027 through 2029 and 0% in 2030. Front-desk staff should set that expectation with the patient before the procedure to avoid surprises.
Is modifier PT still used in 2026?
Yes. Modifier PT remains current, and the reduced-coinsurance phase-in runs through 2029 before reaching zero in 2030, per the CMS Claims Processing Manual and the Consolidated Appropriations Act of 2021. It stays essential for any practice billing Medicare screening colonoscopies.
