CPT code 86334 – Serum immunofixation electrophoresis

Key takeaways

CPT code 86334 covers immunofixation electrophoresis on serum only. Urine, CSF and other fluids take 86335, and mixing the two up is the most frequent coding error on this code.

Medical necessity must be documented on every claim, including reflex orders triggered by an abnormal SPEP result. The automatic reflex workflow does not waive the ICD-10 requirement.

Medicare pays 86334 under the Clinical Laboratory Fee Schedule (CLFS), at the lesser of the lab’s charge or the CLFS rate. CMS updates that rate every year.

Pabau’s claims management software validates each claim for missing or invalid details before submission and flags any rejected claim for a quick fix.

CPT code 86334: Official descriptor and quick-reference summary

CPT code 86334 is classified under the Pathology and Laboratory section of the American Medical Association’s CPT code set, specifically within the Immunology subsection (86000-86849). The official descriptor reads: Immunofixation electrophoresis; serum. The code covers the lab test that identifies the heavy-chain class and light-chain type of a monoclonal protein in serum.

The specimen qualifier, serum, is the word that separates 86334 from its neighbor 86335. Get it wrong and the claim denies. The table below captures the key reference fields coders need at a glance.

What does CPT 86334 cover? Procedure overview

CPT 86334 covers immunofixation electrophoresis on a serum sample. The test separates blood proteins with an electrical current, then overlays antisera specific to each immunoglobulin class to characterize any abnormal band.

It confirms whether an M-protein (a monoclonal immunoglobulin, also called a paraprotein or M-spike) is present. It also determines that protein’s heavy-chain class and light-chain type.

What the test identifies specifically:

• Heavy-chain class: IgG, IgA, IgM, IgD or IgE
• Light-chain type: Kappa or lambda
• Presence of a monoclonal versus polyclonal protein pattern
• Free light chains are quantified separately (CPT 83521), not by 86334

What 86334 does not cover: Immunofixation performed on urine or any body fluid other than serum. That work is billed under CPT 86335. A urine specimen on an 86334 claim is a specimen-mismatch denial waiting to happen.

Clinical indications: When is 86334 ordered?

Medical necessity for CPT code 86334 requires a documented clinical indication in the ordering provider’s record. Payers, especially Medicare, check the indication against their applicable LCD before approving payment.

Accepted indications include:

• Suspected multiple myeloma (C90.00): Bone pain, hypercalcemia, renal insufficiency, or anemia in the context of an elevated total protein or abnormal SPEP band
• MGUS monitoring (D47.2): Periodic surveillance of monoclonal gammopathy of undetermined significance to detect progression to myeloma
• Waldenström macroglobulinemia (C88.0): Workup for IgM-secreting lymphoplasmacytic lymphoma
• Amyloidosis workup (E85.x): Characterizing the immunoglobulin light chain responsible for amyloid deposition
• Abnormal SPEP result: Reflex or follow-up IFE after protein electrophoresis identifies a suspicious band (84165)
• Unexplained neuropathy or renal disease: Clinical suspicion for a plasma cell dyscrasia driving the symptom

Each indication must map to a covered ICD-10-CM code on the claim. Ordering 86334 for routine screening without a specific indication is not covered under Medicare or most commercial LCDs.

Covered ICD-10 diagnosis codes for CPT 86334

The ICD-10-CM codes below are the ones MAC LCDs cite most often as supporting medical necessity for serum immunofixation electrophoresis. Coverage lists change periodically, so confirm the current list in the LCD for your billing jurisdiction before submitting.

Select the ICD-10 code that reflects the ordering provider’s documented clinical finding at the time of the order. A code more specific than the clinical evidence supports creates audit risk. An overly vague code may not satisfy the LCD’s covered-indication requirements.

CPT 86334 vs CPT 86335: Choosing the code by specimen type

The specimen source is the only distinction between these two codes. A coder who misses it submits the wrong code and triggers a denial, which means a corrected claim, delayed payment and staff rework. The table below makes the split explicit.

A myeloma workup often includes both codes on the same date of service: 86334 for the serum IFE and 86335 for the urine IFE. When billing both, document each specimen type clearly in the lab report and on the requisition.

The flow below shows where each code sits in a typical M-protein workup, and what the claim needs before it goes out.

CPT 86334 vs CPT 84165: Immunofixation vs protein electrophoresis

These two codes describe sequential steps in an M-protein workup, not alternatives. Serum protein electrophoresis (SPEP, billed as CPT 84165) detects whether an abnormal protein band exists. Immunofixation electrophoresis (IFE, billed as CPT 86334) then identifies the band’s immunoglobulin class and light-chain type.

Billing 84165 and 86334 together on the same claim is standard practice in a comprehensive myeloma workup. The key documentation requirement: The ordering note must justify both tests, whether ordered simultaneously or as a reflex sequence.

Reflex testing: Billing 86334 when it follows an abnormal SPEP

Reflex ordering is one of the most common workflows for CPT code 86334, and one of the most common causes of incomplete documentation. When an SPEP result shows an abnormal band, many labs automatically add IFE to the same accession. The billing implication: The reflex does not waive the medical necessity requirement.

How to bill a reflex IFE correctly:

1. Same date of service, separate line items: Bill 84165 and 86334 as separate CPT codes on the same claim with the same date of service.
2. Document the reflex trigger: The lab report or ordering note must show the abnormal SPEP finding that triggered the IFE. “Abnormal band noted on SPEP; IFE added per reflex protocol” is sufficient language.
3. Include a covered ICD-10 code: The diagnosis code must appear on both line items. R77.9 (abnormal plasma protein) or the specific clinical diagnosis (C90.00, D47.2) supports the reflex workflow.
4. Payer pre-authorization: Most Medicare and commercial LCDs do not require prior authorization for reflex immunofixation. Still, verify your payer’s policy, because some plans require authorization even for reflex add-ons.
5. Issue an ABN when indicated: Check whether the ordering diagnosis appears in the applicable LCD’s covered-indication list. If it does not, present an Advance Beneficiary Notice (ABN, form CMS-R-131) to the patient before the test is performed. Without a signed ABN, the lab cannot bill the patient if Medicare denies the test.

Medicare reimbursement for CPT 86334: CLFS rate and payer policies

Medicare reimburses CPT 86334 under the Clinical Laboratory Fee Schedule (CLFS), not the Physician Fee Schedule. The Centers for Medicare & Medicaid Services (CMS) publishes the national limitation amount every year. Verify the current calendar-year rate in the CMS CLFS files before quoting a figure to a patient or payer.

How Medicare pays for lab codes:

• The lab bills its standard charge for 86334
• Medicare pays the lesser of the billed charge or the CLFS national limitation amount
• There is no Medicare Part B deductible or coinsurance for most clinical lab tests billed directly by the lab
• Medicaid rates are set by each state and vary widely, so confirm the current rate with your state Medicaid agency
• Commercial payer rates are negotiated and may be above or below the CLFS rate

Local coverage determinations (LCDs) that govern CPT 86334

Medicare Administrative Contractors (MACs) issue LCDs that define the covered indications, covered ICD-10 codes and documentation requirements for immunofixation electrophoresis in their jurisdiction. No single national coverage determination (NCD) governs 86334, so coverage is MAC-specific.

Key MACs with relevant LCDs include Novitas Solutions, CGS Administrators, Palmetto GBA, and Noridian Healthcare Solutions. Each publishes its LCD through the CMS LCD search database. To locate the applicable LCD for a specific claim:

1. Go to the CMS LCD database at cms.gov and search for “immunofixation electrophoresis”
2. Filter by your MAC jurisdiction (the MAC serving the state where the lab performed the test)
3. Confirm the covered-diagnosis list, frequency limitations, and documentation requirements
4. Check the LCD’s “Indications and Limitations of Coverage” section for any non-covered diagnoses that would require an ABN

Good medical billing compliance means reviewing the applicable LCDs when you onboard a new test code, and whenever a MAC issues a proposed revision notice. A policy change applies from its effective date, not from the date you notice it.

Documentation requirements to support CPT 86334

Every CPT 86334 claim needs a documentation trail that connects the ordered test to a specific clinical indication. A lab report alone is not enough, because the ordering provider’s record carries the weight of the medical necessity determination.

Required documentation checklist:

• Clinical indication in the progress note: The ordering provider’s note must document the symptom, finding or diagnosis that prompted the test. Examples include bone pain, anemia, hypercalcemia, an abnormal band on a prior SPEP or a known MGUS diagnosis.
• ICD-10-CM code on the requisition: The diagnosis code on the claim must match the clinical finding documented in the record. It cannot be a code the lab selected independently.
• Specimen source clearly noted as serum: Lab documentation must confirm the specimen was serum, not urine or another fluid. This is what justifies 86334 over 86335.
• ABN if the indication is non-covered: When the ordering indication falls outside the LCD’s covered-diagnosis list, the patient must sign an ABN before the test. Append modifier GA when the ABN is on file, or GZ when none was obtained.
• Reflex authorization language (if applicable): For automatic reflex orders, document the trigger (the abnormal SPEP result) in the lab report or the provider’s notation.
• Ordering provider information: Name, NPI and contact information for the ordering provider. The lab needs them for the claim, and Medicare may request them during an audit.

Strong medical billing documentation habits reduce audit exposure and are the fastest path to first-pass claim acceptance. Generating a complete superbill with every required field before the claim leaves the lab costs far less than working a denial.

Common denial reasons for CPT 86334 and how to avoid them

Most 86334 denials fall into a small number of categories. The table below maps each denial type to its root cause and the steps that prevent or correct it.

A structured denial management workflow categorizes each denial by root cause and tracks resolution time. It is the most reliable way to cut the recurring denials that drain lab billing revenue.

Tracking denial codes by frequency shows which coding or documentation error costs the most, so you can fix it at the source. A clean claim on the first pass carries the correct code, a covered ICD-10 code and complete documentation. It is always cheaper than working the denial queue.

Bundling rules and CCI edits affecting CPT 86334

The Correct Coding Initiative (CCI) edits from CMS define which CPT codes cannot be billed together without a modifier. They also define which codes are bundled into a primary code. For CPT code 86334, the most relevant bundling questions involve adjacent immunology codes.

Key bundling guidance:

• 84165 and 86334 (same DOS): No CCI column I/II edit is expected to prohibit same-day billing of SPEP and serum IFE. They measure different things. Verify against the current quarterly AAPC CPT code reference or the official CCI table, which CMS updates quarterly.
• Immunoglobulin quantification codes (82784, 82785): These codes measure immunoglobulin levels by nephelometry or turbidimetry, a different method from IFE. They are generally separately billable alongside 86334, but confirm this against the current CCI table.
• 86335 and 86334 (same DOS, same specimen): Billing both for a single specimen type is a bundling error. Both are payable only when serum and urine specimens are each independently tested and documented.
• Interpretation codes: The lab technical component and physician interpretation are generally included in 86334 as billed by the performing lab. If a different provider writes a separate physician review and report, modifier 26 may apply, so consult your payer’s policy.

CCI edits change quarterly. Always check the current version before assuming a code pair is or is not separately payable.

How Pabau keeps CPT 86334 claims clean before they go out

When billing runs on spreadsheets and a separate clearinghouse portal, staff check the specimen code, diagnosis and ABN status by hand. Every rekeyed field is another chance for an 86335 to land on a serum claim.

Pabau’s claims management software raises each claim from the patient’s invoice and validates it for missing or invalid details before it leaves. In the US, Pabau submits CMS-1500 claims through Claim.MD to thousands of payers and checks eligibility before the visit.

If a claim comes back rejected, Pabau flags it as Needs action and links straight to the field that needs correcting. Payments then settle from electronic remittance advice (ERA) files, so your team spends its time on the few claims that need judgment.

Get CPT 86334 claims paid on the first pass

Pabau validates each claim for missing or invalid details before it leaves, submits it through your clearinghouse and tracks it from Pending to Paid. Your billing team only works the claims that need a fix.

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Conclusion

Serum IFE is rarely a hard code to choose. The denials come from the paperwork around it. A urine specimen gets billed as serum, a reflex order has no recorded trigger, or a non-covered diagnosis goes out without an ABN.

Fix those three at the requisition, before the test runs, and 86334 becomes one of the more predictable codes in a myeloma workup. Leave them to the denial queue, and each denied claim costs a second round of work.

Book a demo to see how Pabau checks each lab claim before it goes out, so serum IFE claims get paid the first time.

Continue your research

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Want to understand how clearinghouse submission works for CPT codes? Medical claims clearinghouse guide explains the 837P transmission path and how payer responses are handled.

Looking to build a structured denial prevention process? Revenue cycle management for labs and practices outlines the end-to-end workflow from order through remittance.

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