Modifier AS- Assistant at Surgery

Modifier AS is used to identify eligible assistant-at-surgery services furnished by a physician assistant, nurse practitioner, or clinical nurse specialist.

Home > All Categories > Surgical Modifiers > Modifier AS

What is Modifier AS?

Modifier AS identifies assistant-at-surgery services furnished by a physician assistant (PA), nurse practitioner (NP), or clinical nurse specialist (CNS) when the underlying surgical procedure qualifies for assistant-at-surgery reimbursement.

The modifier communicates both the role performed and the type of qualified nonphysician practitioner providing the assistance. It is appended to the applicable surgical procedure code when payer requirements for assistant-at-surgery services are satisfied.

Modifier AS does not make every surgical procedure eligible for assistant-at-surgery payment. The underlying procedure must permit an assistant at surgery, the assistance must be medically necessary when required by the payer, and documentation must support the practitioner's participation.

When to Use Modifier AS

PA Provides Surgical Assistance: Modifier AS may be reported when a physician assistant serves as an assistant at surgery for an eligible procedure.

NP Provides Surgical Assistance: A nurse practitioner performing qualifying assistant-at-surgery services may use Modifier AS when applicable payer requirements are met.

CNS Provides Surgical Assistance: Modifier AS can also identify qualifying assistant-at-surgery services furnished by a clinical nurse specialist.

Procedure Allows an Assistant at Surgery: The underlying surgical procedure must be eligible for assistant-at-surgery reimbursement under the applicable payer's rules.

Practitioner Actively Assists the Surgeon: Documentation should establish that the PA, NP, or CNS performed substantive assistant-at-surgery duties rather than simply being present during the procedure.

When NOT to Use Modifier AS

Physician Assistant Surgeon: Modifier AS specifically identifies PA, NP, or CNS assistant-at-surgery services. Physician assistant surgeons generally use the applicable physician assistant-at-surgery modifier instead.

Procedure Does Not Permit an Assistant: Do not append AS when the underlying surgical procedure is not eligible for assistant-at-surgery reimbursement.

Practitioner Is Only Observing: Presence in the operating room without performing qualifying surgical assistance does not support Modifier AS.

Routine Staff Assistance: Services normally performed by operating-room staff do not automatically qualify as separately reportable assistant-at-surgery services.

Documentation Does Not Support Assistance: The modifier should not be reported when the operative record fails to establish the practitioner's active role in the surgery.

Billing Example

A surgeon performs an eligible complex surgical procedure with a physician assistant serving as the assistant at surgery. The PA actively assists with exposure of the operative field, tissue handling, and other qualifying surgical tasks.

The physician assistant reports the applicable surgical procedure code with Modifier AS to identify the service as assistant-at-surgery care furnished by a qualified nonphysician practitioner.

The operative report should identify the PA and describe the assistant's participation sufficiently to support the reported service.

Documentation Requirements

Assistant Identification: Clearly identify the PA, NP, or CNS who served as the assistant at surgery.

Assistant Role: The operative report should establish that the practitioner actively participated as an assistant rather than merely being present.

Services Performed: Document relevant surgical assistance, such as exposure, retraction, tissue handling, hemostasis, closure, or other substantive activities when applicable.

Primary Surgeon: Identify the surgeon responsible for performing the primary surgical procedure.

Medical Necessity: When required, documentation should support why an assistant at surgery was necessary for the procedure.

Operative Report: Maintain a complete operative report supporting the underlying surgery and the assistant's participation.

Billing and Claim Considerations

Modifier AS should be appended to the eligible surgical procedure code reported by the PA, NP, or CNS furnishing the assistant-at-surgery service.

Not every procedure permits separate payment for an assistant at surgery. Providers should verify the assistant-at-surgery payment indicator or applicable payer policy for the specific procedure before submitting the claim.

Payment for assistant-at-surgery services is generally different from reimbursement for the primary surgeon's service. The modifier identifies the practitioner's role but does not guarantee reimbursement.

Providers should also ensure that the claim accurately reflects the practitioner who furnished the service and that the operative documentation corresponds with the reported assistant-at-surgery arrangement.

Common Billing Mistakes

Using AS for a Physician Assistant Surgeon: Modifier AS is intended for PA, NP, and CNS assistant-at-surgery services. Physician assistant surgeons have different modifier reporting requirements.

Ignoring Procedure Eligibility: Reporting AS on a procedure that does not permit assistant-at-surgery reimbursement can result in denial.

Reporting Routine Operating-Room Assistance: Tasks performed as part of ordinary operating-room staffing should not automatically be billed as a separate assistant-at-surgery service.

Failing to Identify the Assistant: The operative report should clearly identify the practitioner who assisted with the procedure.

Insufficient Description of Participation: Simply documenting "assistant present" may not adequately establish that qualifying assistant-at-surgery services were furnished.

Assuming AS Guarantees Payment: The modifier identifies the practitioner's role. Coverage and reimbursement still depend on the procedure and payer requirements.

Common Denial Reasons

Procedure Is Not Eligible for an Assistant: The payer determines that assistant-at-surgery services are not separately payable for the reported procedure.

Practitioner Type Is Incorrect: The provider reporting AS does not meet the payer's requirements for a PA, NP, or CNS assistant at surgery.

Medical Necessity Is Not Supported: When justification is required, the documentation does not demonstrate why an assistant was necessary.

Operative Documentation Is Insufficient: The operative report fails to identify the assistant or adequately describe the practitioner's involvement.

Incorrect Modifier Reporting: The claim uses AS when another assistant-at-surgery modifier more accurately describes the provider or circumstances.

Underlying Procedure Is Denied: A denial of the primary surgical procedure may also affect payment for the associated assistant-at-surgery service.

Modifier AS vs. Modifier 80

Both modifiers identify assistant-at-surgery services, but the type of provider is different.

Modifier AS identifies qualifying assistant-at-surgery services furnished by a physician assistant, nurse practitioner, or clinical nurse specialist.

Modifier 80 identifies an assistant surgeon and is generally associated with physician assistant-at-surgery reporting.

Selecting the appropriate modifier requires identifying who actually assisted with the procedure and applying the payer's assistant-at-surgery rules.

Related Modifiers

Modifier 80

Modifier 81

Modifier 82