HCPCS code S0145 – Pegylated interferon alfa-2a injection

Key takeaways

HCPCS code S0145 reports pegylated interferon alfa-2a (Pegasys), 180 mcg per mL, given by subcutaneous injection for chronic hepatitis C and B.

S0145 is a non-Medicare S-series code, so traditional Medicare Part B does not accept it and Part B claims use J3490 instead.

Bill one unit per 180 mcg dose, and add the 11-digit NDC when the payer requires it.

Pegylated interferon alfa-2b is a different drug with its own code, S0148, billed per 10 mcg.

Pabau, practice software with built-in claims management, submits S0145 claims and tracks each one through to payment or denial.

HCPCS code S0145: official descriptor, code set, and status

HCPCS code S0145 reports the drug Pegasys (pegylated interferon alfa-2a), billed at one unit per 180 mcg dose. Its official descriptor is Injection, pegylated interferon alfa-2a, 180 mcg per mL. CMS HCPCS documentation, AAPC Codify, and the NCI CanMED ontology all confirm this wording. The code belongs to the S-series of HCPCS Level II codes, temporary codes maintained by the Blue Cross Blue Shield Association rather than CMS.

That ownership has a direct billing consequence. CMS leaves S-series codes out of the Medicare Physician Fee Schedule and sets no national payment rate for them. As a result, S0145 is accepted mainly by commercial payers and by state Medicaid programs that have added BCBSA codes to their own fee schedules.

What S0145 covers: clinical indications and drug profile

Pegylated interferon alfa-2a (Pegasys) is an antiviral immunomodulator. The FDA approved it for chronic hepatitis C virus (HCV) infection in adults (and certain pediatric patients per label) with compensated liver disease. It is also approved for chronic hepatitis B virus (HBV) infection in adults (and certain pediatric patients per label). It is given as a once-weekly subcutaneous injection, often combined with ribavirin in HCV regimens.

For billing purposes, S0145 covers the drug itself, not the administration service. When the practice gives the injection, the administration is reported separately, usually with CPT 96372. Payers reject a claim that bundles the drug and the administration on one line, so they must appear as separate claim lines.

• Primary indication (HCV): Chronic hepatitis C in adults (and certain pediatric patients per label) with compensated liver disease
• Secondary indication (HBV): Chronic hepatitis B, HBeAg-positive or HBeAg-negative, in adults (and certain pediatric patients per label)
• Combination therapy: Often co-administered with ribavirin for HCV; ribavirin is billed separately under its own HCPCS or NDC-based code
• Route: Subcutaneous injection only; this code does not apply to intravenous administration
• Excluded from this code: Other interferon formulations (alfa-2b, beta-1a, gamma) and non-pegylated interferon alfa-2a products

How to bill S0145: units, dosage, and claim line reporting

Bill one unit of HCPCS code S0145 per 180 mcg dose administered. The descriptor’s “per mL” wording matches the standard Pegasys vial, which holds 180 mcg in 1 mL. At the most common dose, one vial equals one billing unit. Some patients receive a different dose, such as 135 mcg after a dose reduction. In that case, check the payer’s billing guidelines for unit calculation, because conventions vary by plan.

An accurate S0145 claim line needs the elements below before submission. Missing any one of them triggers an automated edit at the clearinghouse. If you are newer to the claim cycle, how medical billing works shows where each element enters it.

1. Code: S0145 in the procedure code field
2. Units: Number of 180 mcg doses administered on the date of service
3. NDC number: 11-digit National Drug Code for the specific Pegasys lot dispensed (required by many payers; format: 5-4-2 with leading zeros)
4. NDC unit: Report in milliliters (ML) with quantity equal to the volume administered
5. Diagnosis code(s): ICD-10-CM code(s) supporting medical necessity (see the ICD-10 section below)
6. Prior auth number: Insert in the authorization reference field if the payer required PA for this dispensing
7. Place of service: Typically 11 (office) or 22 (outpatient hospital); confirm with payer

A clean S0145 claim line also includes the prescribing clinician’s NPI in the ordering/referring field. Some commercial payers and Medicaid programs require the supervising physician’s NPI separately from the rendering provider’s. Review the payer-specific billing guide for that distinction before submitting a batch. Keeping these values on the patient record in claims software for practices means the biller checks each one instead of retyping it.

ICD-10-CM diagnosis codes to report with HCPCS code S0145

Pairing S0145 with the correct ICD-10-CM code is the single fastest way to avoid a medical-necessity denial. The diagnosis must reflect the documented, active clinical condition being treated, not a historical or resolved diagnosis. Use the most specific code available for the patient’s documented genotype and disease status.

Codes that will trigger automatic denial: unspecified viral hepatitis (B19.9), resolved hepatitis (Z86.19), or acute hepatitis without chronic documentation. Also avoid pairing S0145 with a diagnosis for a different interferon indication, such as multiple sclerosis. Payers cross-check the diagnosis against the drug class.

S0145 vs. J codes: choosing the correct code for interferon billing

S0145 is an S-series code, not a J-code, and that distinction determines which payers will process the claim. J-codes are CMS-maintained HCPCS Level II codes used primarily for Medicare Part B drug billing. S-codes are BCBSA-maintained temporary codes used by commercial and some Medicaid payers. The two series coexist in the HCPCS Level II system but serve different payer populations.

Traditional Medicare does not accept S0145 as a valid billing option for its beneficiaries. The standard workaround is J3490, the unclassified drug code, with the drug name and dose in the claim’s remarks field. Some Medicare Advantage plans follow commercial coding conventions and may accept S0145 directly. Always verify with the specific MA plan before submitting, and use the chart below to match each payer type to its code.

Payer coverage and S0145 fee schedule reimbursement

There is no single national fee schedule for HCPCS code S0145 because CMS does not set a rate for S-series codes. Each payer establishes its own allowed amount. Reimbursement rates vary substantially across commercial plans, state Medicaid programs, and managed care organizations. Any specific dollar figure cited elsewhere without a payer name and effective date is likely outdated or inapplicable to your contract.

Medicare coverage status

Traditional Medicare Part B does not cover S0145. CMS does not maintain S-series codes in the Medicare Physician Fee Schedule. Claims sent to traditional Medicare with S0145 come back as invalid procedure codes. For these patients, bill J3490 with a written drug description. Your Medicare Administrative Contractor (MAC) can give jurisdiction-specific guidance on outpatient billing for this drug.

• Medicare Part B: Not covered; submit J3490 with drug description instead
• Medicare Part D: Pegasys may be covered as a pharmacy benefit under some Part D plans; check the plan formulary
• Medicare Advantage: Coverage varies by plan; confirm directly before billing S0145

Commercial and Medicaid payer acceptance

Most BCBSA-affiliated commercial plans recognize S0145 and apply their own contracted fee schedule rates. According to the CMS Healthcare Common Procedure Coding System documentation, S-codes are temporary codes for payers that choose to adopt them. Acceptance is decided payer by payer rather than mandated nationally.

Indiana Medicaid issued bulletin BT202579 specifically referencing S0145, which provides documented evidence of at least one state Medicaid program accepting this code. Other state Medicaid programs have varying policies. Check your state’s Medicaid provider manual or fee schedule before assuming S0145 is accepted.

To look up reimbursement rates: use the AAPC Codify HCPCS lookup for code descriptor reference, then query the specific payer’s drug fee schedule or portal. Many commercial payers publish S-code rates on their provider portals. Look under the pharmacy or specialty drug fee schedule, which is separate from the medical fee schedule.

Prior authorization requirements for S0145

Prior authorization is required by most payers for S0145. Pegylated interferon alfa-2a is a specialty biologic, and payers routinely apply medical-necessity review before approving reimbursement. A claim without a required PA number will be denied. Retrospective PA approval is rarely granted for this drug class.

Confirming coverage and PA requirements before dispensing is the single most impactful step a billing team can take. An insurance eligibility verification workflow records whether a PA is required during the pre-service check. That avoids a last-minute scramble when the patient arrives for the injection.

• Genotype report: The HCV genotype result must be on file, and some payers require it in the PA submission
• Viral load: Baseline HCV RNA or HBV DNA quantification result
• Liver fibrosis stage: FibroScan, liver biopsy, or validated non-invasive scoring where available
• Treatment history: Prior treatment courses, response, and any treatment failures or contraindications to alternative agents
• Prescriber attestation: Statement of medical necessity from the ordering physician
• Diagnosis code: ICD-10-CM code matching the approved clinical indication

Aetna Clinical Policy Bulletin 0404 sets out the medical-necessity criteria for interferons, including pegylated interferon alfa-2a. It is public, so it works as a reference for what commercial payers commonly require. Reviewing a payer’s active clinical policy bulletin before submitting a PA reduces the back-and-forth that extends approval timelines.

Documentation requirements for S0145 claims

Thorough documentation is the foundation of a defensible S0145 claim. This drug is high-cost and subject to payer audit. The patient’s chart must support every element of the claim line at the time of submission. Adding documentation after a denial audit creates compliance risk, so complete the records before the claim is sent.

Consistent documentation practices across all injectable drug administrations support both clean-claim rates and post-payment audit defense. Medical billing compliance frameworks recommend treating drug-claim documentation as a standing checklist rather than a case-by-case judgment call.

• Prescriber order with drug name (Pegasys or peginterferon alfa-2a), dose (mcg), route (subcutaneous), and frequency
• Active ICD-10-CM diagnosis code matching the approved indication
• Most recent viral load or HBV DNA result and date drawn
• Genotype result (HCV patients)
• NDC number for the specific lot dispensed, with expiration date
• Dose administered on the date of service and any dose modification rationale
• Prior authorization number and effective date range if PA is required
• Administering clinician’s credentials and supervising physician NPI if required by payer

Common claim denial reasons for S0145 and how to resolve them

S0145 denials follow predictable patterns. Most result from a code-payer mismatch, a missing PA, or incomplete documentation rather than from coverage exclusions. Reviewing the explanation of benefits (EOB) remark codes and mapping them to the specific fix below resolves most denials at the first appeal level.

A structured approach to denial management in healthcare sorts denials by root cause. Billers can then batch similar appeals and fix the recurring cause instead of treating each denial as a one-off.

Codes commonly confused with S0145

Several HCPCS codes describe interferon products or adjacent drug classes, and selecting the wrong one is easy when working from a drug name alone. The table below identifies the codes billers most frequently confuse with S0145 and the deciding factor for each.

The S0145 vs. S0148 confusion is the most clinically consequential. Both are pegylated interferons, but alfa-2a (S0145, Pegasys) is billed per 180 mcg and alfa-2b (S0148) per 10 mcg. The two differ in pegylation structure, dosing schedule, and payer coverage policy. Verify the prescribing order specifies “alfa-2a” or “Pegasys” before coding. Use the PGM Billing HCPCS lookup tool or the NLM HCPCS Level II API to cross-reference the descriptor against the drug dispensed.

How claims management software supports S0145 claims

Many billing teams key each S0145 claim by hand, then check payer portals to see whether it was paid. A J3490 claim sent as S0145, or a missing PA number, often goes unnoticed until the denial arrives.

Pabau’s claims management submits the claim from the visit’s billing record and tracks its status afterward. Accepted, paid, and denied claims sit in one list, so nobody has to log in to each payer to find out.

The result is faster follow-up. A denied S0145 line shows up while the PA letter and NDC record are still easy to find, so the corrected claim goes out sooner.

Keep every S0145 claim tracked to payment

Pabau’s claims management submits HCPCS drug claims and tracks each one to payment or denial. Your billing team sees which S0145 claims need follow-up without checking payer portals one by one.

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Conclusion

HCPCS code S0145 has a simple descriptor, but the claim only pays when the payer, diagnosis, documentation, and unit count line up. Check the payer first, because that one step decides whether the claim carries S0145 or J3490.

Then build the claim from the chart before it goes out. Rebuilding records after a denial takes longer and carries more audit risk than getting them right at submission.

Pabau’s claims management helps your team submit S0145 claims and track each one through to payment or denial. Book a demo to see how it keeps your drug claims visible after submission.

Continue your research

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