The American Cancer Society predicted the diagnosis of over 2 million new cancer cases in 2025. Cancer remains one of the most complex and challenging conditions in modern medicine, and oncologists worldwide are fighting it.
Before treatment, the patient undergoes scanning to determine the areas affected by cancer. Among these methods, positron emission tomography (PET) scanning is used for cancer staging, and it is one of the most expensive imaging services billed by practices.
Moreover, Medicare claims are highly sensitive to coding accuracy, and errors may result in denials or unprocessable claims. Therefore, medical billing teams use the PI modifier to indicate that the scan was performed to guide the patient’s initial treatment strategy for cancer.
However, using it incorrectly triggers claim rejection. Thus, professionals must learn this modifier’s usage guidelines and applicable scenarios.
PI Modifier – Description
The PI modifier is an HCPCS Level II modifier defined by the Centers for Medicare & Medicaid Services (CMS) as:
“Positron Emission Tomography (PET) or PET/Computed Tomography (CT) that informs initial treatment for a biopsy-proven or strongly suspected cancerous tumor based on other diagnostic testing.”
CMS created the modifier in the Transmittal R1833, and it has been active for insurance billing since April 3, 2009. Many times, the PS modifier (used for subsequent anti-tumor treatment strategy after a patient’s initial therapy) is considered a companion for modifier PI.
What does the PI modifier’s coverage involve?
Understanding CMS Coverage for Modifier PI
According to the CMS National Coverage Determination (NCD) 220.6.17, Medicare covers one fluorodeoxyglucose (FDG) PET study when it is used to plan the patient’s initial treatment strategy. However, this applies when a beneficiary’s physician in charge requires the scan to:
- Determine whether a patient can go through an invasive diagnostic or therapeutic procedure.
- Identify the optimal anatomic location for the invasive procedure.
- Determine the extent of the tumor in cases where the anti-tumor treatment may be altered based on the current condition.
Appropriate Use Cases for PI Modifier
Now that we have discussed the basics of this modifier, let’s move on to its usage. Modifier PI is used for oncologic conditions. However, its accurate usage may confuse new medical billers.
Therefore, it is imperative to review a few appropriate use cases for this modifier to develop a deeper understanding.
Newly Diagnosed Multiple Myeloma
Say a 71-year-old male Medicare beneficiary presents with progressive bone pain and fatigue. The patient also suffers from anemia.
Laboratory results reveal a serum monoclonal protein elevation, and multiple myeloma is confirmed with a bone marrow biopsy.
The oncologist suggests systemic therapy, but before it, the hematologist orders an FDG PET/CT to determine focal skeletal lesions or extramedullary disease. It will also help assess the overall anatomic burden of disease, guiding the induction regimen.
Since Medicare provides coverage for FDG PET imaging when used for the initial treatment strategy in cases of myeloma, the imaging facility and interpreting physician append the PI modifier to the claim to indicate this.
Newly Diagnosed Lung Cancer
Consider the case of a 68-year-old Medicare beneficiary who presents with a right upper lobe lung mass on CT.
The oncologist orders an FDG PET/CT to determine the anatomic extent of disease and scan for distant metastases for initial staging. Based on PET/CT findings, a CT-guided biopsy is performed on the lung mass, and pathology confirms lung cancer.
The oncologist must then choose between surgery, systemic therapy, or radiation based on the staging results.
Since the patient has a biopsy-proven cancer and the PET/CT is used to select the patient’s first treatment decision, the modifier PI applies. Hence, the imaging facility and the interpreting physician append the PI modifier to the claim to bill the payer.
Biopsy-Proven Lymphoma
Consider the case of a 54-year-old patient who appears at the oncologist’s clinic with painless cervical lymphadenopathy. The specialist evaluates the patient and reviews prior diagnostic findings.
The patient’s CT imaging and laboratory findings strongly indicate lymphoma. Thus, the physician orders an FDG PET/CT scan to determine the nodal involvement. This allows the experts to devise an eventual treatment plan based on the cancer progression.
Since the patient has a biopsy-proven malignancy and the procedure is used to select the patient’s first treatment decision, the team uses the PI modifier.
Note: Sometimes, medical billing teams confuse modifiers PI and PS, but they are distinct. The PI modifier indicates scans for the initial treatment plan. On the other hand, modifier PS indicates a later treatment plan for a cancerous tumor.
Accurate Usage Guidelines for PI Modifier
Accurately using the PI modifier may sound simple, but it is not. The following is a list of accurate usage guidelines to consider:
1. Append with Appropriate CPT Codes Only
According to the CMS Transmittal R1833CP, modifier PI can be appended to FDG PET CPT codes. However, it can rightfully be appended to the following codes only:
- 78608
- 78811
- 78812
- 78813
- 78814
- 78815
- 78816
If the medical billing team uses PI on other CPT codes, the claim will be denied and considered non-processible.
2. Review the Scan and Coverage
Medicare and some other commercial payers cover FDG PET for the initial treatment strategy. The staging procedure applies to solid tumors and myeloma.
It may also apply to breast cancer for axillary nodal staging and the early stages of cervical cancer. Therefore, it is necessary to check the NCD’s synopsis table before billing the payer to avoid errors.
3. Append PI to Technical & Professional Claims
According to Radiology Today, the PI modifier must be reported in either the second, third, or fourth modifier position to the facility claim (technical component – modifier TC) and professional claim (physician interpretation – modifier 26) when both components are being billed separately.
- Stay Inside the Per-Cancer Scan Limit
According to the CMS Transmittal R3162CP, the PI modifier can only be appended when coverage is applicable and limited to the PET scan for initial staging. Moreover, CMS allows limited follow-up PET scans (reported with modifier PS) per cancer diagnosis, subject to specific coverage rules and medical necessity.
More importantly, if a provider tries to bill a second “initial” PET scan for that exact same cancer site, the insurance system will flag it as an exception, and human reviewers at the local Medicare contractor, or MAC, must manually decide whether to pay it.
- Justify Medical Necessity
The PI modifier can only be used if the services or procedures rendered are medically necessary. Therefore, the provider must document the patient’s diagnosis and condition before ordering the initial PET scan and submitting a claim for it.
Generally, it applies to the initial anti-tumor treatment plan or the biopsy result. In other cases, it may be appended to a “strongly suspected” malignancy in the documents.
- Do Not Use PI and PS Modifiers Simultaneously
As stated earlier, PI and PS modifiers are unique and should be used according to their requirement. They are both exclusive at a claim line level, and PI particularly applies to an initial strategy, never later.
Streamline Your PI Modifier Claims with NeuraBill
The PI modifier is a two-letter HCPCS Level II code that plays a critical role in PET scan reimbursement. It indicates to the payer that the oncologist performed an initial FDG PET or PET/CT for the patient’s treatment planning of a strongly suspected or biopsy-proven cancer.
Getting it wrong means a denied claim, a re-billing cycle, and most likely revenue loss for your practice.
If your team is spending too much time reworking modifier-related claim rejections, NeuraBill’s medical billing and coding services can take the work off your plate. They have a team of certified professionals who have mastered modifier usage, including modifier PI.
