CPT code 86618 – Borrelia burgdorferi antibody immunoassay

Key takeaways

CPT code 86618 reports an enzyme immunoassay (EIA or ELISA) for Borrelia burgdorferi antibodies. It is the first-tier Lyme screening test, not the confirmatory immunoblot (CPT 86617).

Under the CDC two-tier protocol, 86617 is billed only after a reactive or equivocal 86618 result. Billing both without that documented result is a leading denial cause.

A69.20 (Lyme disease, unspecified) is the diagnosis most often paired with 86618. A pairing outside the MAC’s LCD covered-diagnosis list is denied at adjudication.

Pabau’s claims management software sends 837P claims through Claim.MD, runs eligibility checks, and posts ERA remittances against the patient record.

CPT code 86618: Description, category and clinical scope

CPT code 86618 reports an immunoassay for antibodies to Borrelia burgdorferi, the spirochete that causes Lyme disease. The American Medical Association places it in the Immunology subsection of the Pathology and Laboratory chapter (codes 86000-86849). The test detects IgG and IgM antibodies in a serum specimen, using an EIA or ELISA method.

The test is not CLIA-waived, so only a CLIA-certified laboratory may bill it. Medical billing compliance for lab services also requires the CLIA certificate details on file before any claim goes out.

Use the AAPC Codify CPT lookup to verify the current code descriptor and any annual updates before submitting claims.

Test procedure and specimen requirements

The test requires a serum specimen. A red-top or gold-top (serum separator) tube is collected by venipuncture and centrifuged, and the serum goes to the CLIA-certified laboratory. Some reference labs accept EDTA plasma, but serum is the standard. Confirm specimen requirements with the performing lab before collection.

• Preferred specimen: Serum (red-top or SST tube)
• Volume: Typically 0.5-1 mL of serum, confirmed with the performing lab
• Storage: Refrigerate at 2-8°C if transport is delayed, or freeze at -20°C for longer storage
• Transport: Ship refrigerated and avoid repeated freeze-thaw cycles
• CSF specimens: Cerebrospinal fluid testing for Lyme antibodies may require separate coding, because 86618 is primarily validated for serum. Check the MAC’s local coverage determination (LCD) and the reference lab before ordering

The EIA measures whether patient antibodies bind to Borrelia burgdorferi antigens. A reactive or equivocal result triggers the second tier of the CDC protocol. A negative EIA result, in a patient with low pretest probability, ends the workup without 86617 being ordered or billed.

CPT 86618 vs CPT 86617: When to use each code

CPT 86618 is the first-tier EIA screening test. CPT 86617 is the second-tier immunoblot (Western blot) confirmatory test. The two codes describe different procedures and are not interchangeable.

Ordering 86617 without a reactive or equivocal 86618 result, and billing both on the same claim, is a frequent denial trigger. Document the first-tier result in the chart note before the second tier is ordered.

The CDC two-tier testing protocol and its impact on billing

The Centers for Disease Control and Prevention recommends a sequential two-tier algorithm for laboratory confirmation of Lyme disease. The first-tier result decides which codes are billable on a given date of service, as the chart below sets out.

1. Tier 1: Order CPT 86618 (EIA). Document clinical signs (erythema migrans, joint symptoms, neurologic findings), tick exposure history, and geographic risk in the chart note.
2. Evaluate tier 1 result: If the EIA is negative and clinical suspicion is low, the workup ends. No 86617 is billed.
3. Tier 2 trigger: If the EIA is reactive or equivocal, order CPT 86617 (Western blot). The tier 1 result must be documented in the lab order and the chart note. Payers examine that record when they review a claim with both codes.
4. Billing both codes: When both 86618 and 86617 appear on the same claim, include the first-tier result status and the clinical indication in supporting documentation. Modifier 59 may be required, depending on the NCCI edit table in effect that quarter. Confirm it before billing.

ICD-10 codes to pair with CPT code 86618

The ICD-10-CM code on the claim must establish medical necessity for the Lyme antibody test. Using a code that falls outside the payer’s covered-indication list under the applicable LCD is the most common reason 86618 claims are denied at adjudication.

Verify the covered-diagnosis list in the applicable Medicare Administrative Contractor (MAC) LCD before billing. Z20.818 and R68.89 draw closer scrutiny.

Where the documentation supports it, leading with A69.20 through A69.29 gives the claim the strongest medical necessity case. Use the CDC/NCHS ICD-10-CM web tool to confirm current code descriptions and any exclusion notes.

Medicare and payer coverage rules for CPT 86618

Medicare Part B covers CPT 86618 as a clinical laboratory service when medical necessity is established under the applicable MAC’s LCD. Coverage varies by jurisdiction.

Noridian, Palmetto GBA, and Wellpoint Federal (formerly National Government Services) each maintain their own Lyme serology LCDs, and covered ICD-10 pairings may differ between them.

• No NCD exists for CPT 86618, so coverage is entirely LCD-driven at the MAC level
• CLIA compliance: The laboratory billing 86618 must hold an active CLIA certificate covering the complexity level of this test. Practices billing 86618 under a physician number must confirm the CLIA status is documented
• Advance Beneficiary Notice (ABN): Issue an ABN before the test when the indication may not meet the MAC’s covered-diagnosis criteria. Z20.818 and symptom-only codes are the usual cases
• Private payers: Most major commercial plans follow the CDC two-tier protocol and cover 86618 when it carries a covered ICD-10 code. Medicare rarely requires prior authorization, but select commercial plans may

Run an eligibility check when the test is ordered, so an inactive policy surfaces before the specimen is drawn. Our Claim.MD clearinghouse guide explains how 837P electronic claims move from practice to payer.

Medical necessity documentation requirements

Medical necessity for CPT 86618 rests on what the ordering provider documents before the test is drawn. Payers audit these elements on post-payment review and pre-payment edits for high-volume Lyme jurisdictions.

• Clinical signs and symptoms: Document specific findings, such as erythema migrans rash, arthritis, facial palsy, palpitations, or other objective signs. “Rule out Lyme disease” alone is insufficient under most LCDs
• Exposure history: Record tick exposure, the geographic location of potential exposure, and the time of year. Endemic regions (the northeastern and upper midwestern US) carry more weight with MAC reviewers
• Differential diagnosis: Note other conditions in the differential that the test will help exclude
• Lab order: The requisition must include the ICD-10 code(s) supporting the order. Without one, an audited claim has no documented reason for the test

Weak documentation sits behind most 86618 medical necessity denials. Build these four elements into the visit note template, and a missing one is caught while the patient is still in the room.

Common denial reasons for CPT code 86618 and how to fix them

Five denial patterns recur on 86618 claims. Each has a specific fix that can be built into the pre-submission workflow.

A structured denial management workflow catches these patterns before they become write-offs. Track denial reason codes from remittance advice by CPT code to see which of the five issues hits your practice most.

Corrective action can then target the highest-volume cause first. Our denial codes reference explains how to read the CARC and RARC codes on an EOB or ERA.

Applicable modifiers for CPT code 86618

Four modifiers come up on 86618 claims. Three can apply in common billing scenarios, and the fourth (QW) is a frequent coding error.

Appending QW to CPT 86618 is a compliance error, because the test runs in a CLIA-certified lab rather than a CLIA-waived point-of-care setting. Submitting a clean claim for Lyme serology means verifying that the modifier field is populated correctly (or left blank) before each batch is released.

Reimbursement rates for CPT 86618

The CMS Clinical Laboratory Fee Schedule (CLFS) sets the Medicare Part B allowable for CPT 86618. The national limitation amount is published annually in the CLFS update and applies to independently billing laboratories.

Physician fee schedule rates and geographic adjustments apply in some billing contexts. Check the current rate with CMS each year rather than relying on prior-year figures.

• Rate source: CMS Clinical Laboratory Fee Schedule (Part B, independent labs), updated every January
• Geographic variation: CLFS rates are national limitation amounts, with no geographic adjustment for Part B lab services. Some PFS billing contexts do apply geographic multipliers
• 86618 vs 86617: CPT 86618 (EIA screening) typically reimburses at a lower rate than CPT 86617 (immunoblot), which is a more complex analytical procedure
• Private payer rates: Commercial rates are negotiated and vary significantly from CLFS, so check individual payer contracts

A grounding in medical billing fundamentals helps billing staff see how CLFS and PFS allowables differ. It also makes a short payment easier to spot against the contracted rate.

How claims management software prevents CPT 86618 denials

Most 86618 denials start before anyone opens the billing queue. A wrong ICD-10 pairing, a missing tier-1 result, or an absent modifier is set in motion when the test is ordered and documented.

Pabau, the practice software we build, keeps the visit note, the lab order, and the claim in one patient record. Practices with Labs switched on order Quest tests from that record, and the results import automatically. Billing staff then build the claim from the documented findings, with no re-keyed summary in between.

Pabau’s medical claims management software sends 837P claims through Claim.MD, runs eligibility checks, and posts ERA remittances against the same record. A denied 86618 claim then sits beside the chart note that explains it, so the fix starts from the documentation.

Reduce CPT 86618 denials before they happen

Pabau keeps the chart note, the lab order, and the claim in one patient record. Claims go out through Claim.MD with eligibility checks and ERA remittances, so billing staff work from the documented findings.

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Conclusion

Two facts decide whether an 86618 claim pays on the first pass. The diagnosis code must sit on the MAC’s covered list, and the chart must show why Lyme disease was suspected. If 86617 follows, the tier-1 result has to be on record before the second test is ordered.

Put both checks into the ordering workflow, where they cost a minute, instead of the appeals queue, where they cost weeks. Book a demo to see how Pabau keeps Lyme serology orders, documentation, and claims in one record.

Continue your research

Unfamiliar with the 837P electronic claims process? How 837 files work in medical billing explains the EDI transaction format that carries your CPT and ICD-10 codes to the payer.

New to clearinghouse submission? Medical claims clearinghouse guide walks through how claims are validated, scrubbed, and forwarded before reaching the MAC.

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