Check out These 7 Steps to Coding Colonoscopies After Positive Fecal Results
Here’s how to use Medicare modifier PT. Colorectal cancer screening has changed significantly over the past several years. More patients are beginning their screening journeys with noninvasive tests such as the fecal immunochemical test (FIT) or stool DNA testing (Cologuard®), meaning you’re likely seeing more claims for follow-up colonoscopies after a positive screening result. At first glance, these cases may seem straightforward. A patient has an abnormal FIT, undergoes a colonoscopy, and perhaps even has a polyp removed. But determining whether that colonoscopy is considered screening or diagnostic for coding purposes can become confusing, particularly when Medicare rules, commercial payer requirements, modifiers, and diagnosis sequencing all come into play. Use the following steps to understand how these distinctions can help prevent denials, protect patients from unnecessary cost sharing, and ensure accurate reimbursement. Step 1: Determine Why the Colonoscopy Was Performed Ask this question: “What was the intent of the colonoscopy?” The answer drives much of your coding. There are two types of colonoscopy: A positive FIT or Cologuard® result creates an important exception. Although the patient has an abnormal stool-based screening result, the Centers for Medicare & Medicaid Services (CMS) and many commercial payers now recognize the follow-up colonoscopy as part of the complete colorectal cancer screening process rather than a separate diagnostic service. This distinction affects both coding and patient cost sharing, according to the American Gastroenterological Association. Step 2: Know When a Positive Stool-Based Test Still Represents Screening Historically, many payers treated a colonoscopy performed after a positive FIT or Cologuard® as diagnostic because the physician was evaluating an abnormal finding, but that has changed. Beginning in 2023, Medicare expanded its complete colorectal cancer screening definition to include a follow-on screening colonoscopy after a covered positive stool-based screening test. This includes positive FIT, fecal occult blood testing (FOBT), and multitarget stool DNA testing (Cologuard®), as well as certain blood-based screening tests added later. This means the positive stool test doesn’t automatically convert the colonoscopy into a diagnostic procedure for Medicare screening purposes. Commercial insurance plans often follow the Affordable Care Act (ACA) preventive service requirements, although coding requirements can vary by payer. Step 3: Select the Correct Procedure Code Once you’ve determined the colonoscopy qualifies as a screening examination, choose the CPT® code based on the work the provider actually performed. Examples include: Procedure Performed CPT® Code Diagnostic colonoscopy with no intervention 45378 (Colonoscopy, flexible; diagnostic, including collection of specimen(s) by brushing or washing, when performed (separate procedure)) Colonoscopy with biopsy 45380 (… with biopsy, single or multiple) Colonoscopy with hot biopsy removal 45384 (…with removal of tumor(s), polyp(s), or other lesion(s) by hot biopsy forceps) Colonoscopy with snare polypectomy 45385 (… with removal of tumor(s), polyp(s), or other lesion(s) by snare technique) Remember, CPT® coding reflects the procedure performed, not simply the reason the patient underwent the examination. If a screening colonoscopy becomes therapeutic because the physician performs a biopsy or polypectomy, report the therapeutic CPT® code rather than the screening code. Step 4: Apply the Correct Modifier One of the most common mistakes involves modifier selection. The modifiers commonly associated with screening colonoscopies are as follows: Modifier PT tells Medicare the procedure began as a colorectal cancer screening but was converted to another procedure after pathology was identified. Example: A Medicare patient undergoes a screening colonoscopy. The physician removes a polyp by snare. For this service, you report 45385, but this answer is incomplete. Correct answer: You should report 45385 appended with modifier PT. Without modifier PT, Medicare may process the procedure as an ordinary diagnostic colonoscopy rather than recognizing its screening intent. Example: A 52-year-old asymptomatic patient with commercial insurance has a positive Cologuard® test and undergoes a follow-up colonoscopy. During the procedure, the physician obtains a biopsy, and you report 45380. While the CPT® code accurately reflects the procedure performed, your coding is not yet complete. Correct answer: For many commercial payers, you should report 45380 appended with modifier 33. Modifier 33 indicates that the colonoscopy was performed as part of a recommended preventive screening service, even though a biopsy became necessary during the examination. Reporting modifier 33, when required by the payer, helps identify the service as preventive and may allow the claim to be processed under the patient’s preventive screening benefit. Because commercial payer policies vary, always verify each payer’s specific modifier and billing requirements before submitting the claim. Step 5: Understand Medicare’s Modifier KX Requirement After Positive Stool Testing One of the newest Medicare requirements has caught many coding departments by surprise. When a Medicare beneficiary undergoes a follow-on screening colonoscopy after a positive, covered stool-based screening test, CMS instructs providers to append modifier KX (Requirements specified in the medical policy have been met) to the screening HCPCS Level II code, such as G0105 (Colorectal cancer screening; colonoscopy on individual at high risk) or G0121 (… colonoscopy on individual not meeting criteria for high risk), to indicate the requirements for a complete colorectal cancer screening have been met. Failure to report the required modifier can result in a claim that might be unable to be processed. Be sure your organization’s Medicare workflow reflects current CMS guidance. Step 6: Sequence Diagnosis Codes Correctly Diagnosis code sequencing often creates as much confusion as procedure coding. When the colonoscopy is performed as part of a screening examination, the screening diagnosis code generally remains the primary diagnosis, even if the physician discovers and removes a polyp. Example: An asymptomatic patient undergoes a screening colonoscopy after a positive FIT test. During the procedure, the physician removes a colon polyp. After reviewing the pathology report, you assign K63.5 (Polyp of colon) as the primary diagnosis and Z12.11 (Encounter for screening for malignant neoplasm of colon) as the secondary diagnosis. Although the diagnosis codes accurately reflect the patient’s condition, the sequencing is incorrect. Correct answer: You should report Z12.11 as the primary diagnosis because the colonoscopy was performed as a screening examination. Report K63.5, or the pathology-confirmed diagnosis if more specific, as a secondary diagnosis to capture the finding identified during the procedure. Sequencing the screening diagnosis code first helps reflect the original intent of the examination and supports processing under applicable preventive screening benefits consistent with CMS guidance and many payer policies. However, always verify diagnosis sequencing requirements for the individual payer, as policies may vary. Step 7: Know When the Colonoscopy Truly Is Diagnostic Not every colonoscopy after abnormal testing qualifies as screening. If the patient presents with symptoms, the colonoscopy is generally considered diagnostic, regardless of whether the patient previously had a positive stool-based screening test. Symptoms include: Likewise, if the physician documents the primary indication as evaluation of symptoms rather than completion of colorectal cancer screening, you generally should not report preventive modifiers. Examine These Common Coding Scenarios Scenario 1: A 58-year-old asymptomatic patient has a positive FIT and is referred for a follow-up colonoscopy. The colonoscopy is completed to the cecum, no abnormalities are identified, and no biopsies or other interventions are performed. Correct coding approach: Report 45378, as the procedure consisted of a diagnostic colonoscopy without biopsy or lesion removal. For a Medicare beneficiary, append modifier PT if required to indicate the service was furnished as part of a colorectal cancer screening. For many commercial payers, modifier 33 may be appropriate to identify the service as preventive, depending on the payer’s billing requirements. Report ICD-10-CM code Z12.11 as the primary diagnosis. Even though the colonoscopy was prompted by a positive FIT result, the absence of findings does not change the screening intent of the examination under current CMS colorectal cancer screening guidance. Always verify modifier and diagnosis sequencing requirements with the individual payer. Scenario 2: An asymptomatic patient has a positive multitarget stool DNA test (Cologuard®) and is referred for a follow-up colonoscopy. During the procedure, the physician identifies and removes a 12 mm adenomatous polyp using a snare technique. Correct coding approach: Report 45385, since the physician performed a snare polypectomy. For Medicare beneficiaries, append modifier PT to indicate the procedure began as a colorectal cancer screening but became therapeutic after the polyp was identified. For many commercial payers, modifier 33 may be appropriate to identify the service as a preventive screening, depending on the payer's billing requirements. Report ICD-10-CM code Z12.11 as the primary diagnosis, followed by the pathology-confirmed diagnosis, such as D12.6 (Benign neoplasm of colon, unspecified), or another more specific diagnosis code based on the pathology report. The discovery and removal of a polyp don’t retroactively change the original screening intent of the colonoscopy. As always, verify diagnosis sequencing and modifier requirements with the individual payer, as policies may vary. Pass This Documentation Checklist Before assigning codes, confirm the medical record clearly documents: Remember the Bottom Line Coding colonoscopies after positive FIT or Cologuard® results requires more than selecting the correct CPT® code. You must determine the intent of the procedure, understand when Medicare considers the examination part of a complete colorectal cancer screening, apply the appropriate modifiers, and sequence diagnosis codes correctly. By carefully reviewing the physician’s documentation and following CPT®, CMS, and payer-specific guidance, you can reduce denials, support accurate reimbursement, and help ensure patients receive the preventive benefits intended under current colorectal cancer screening policies. Suzanne Burmeister, BA, MPhil, Medical Writer and Editor
