CPT code 86780 – Treponema pallidum treponemal antibody test

Key takeaways

CPT code 86780 covers the treponemal antibody test for Treponema pallidum, run as an EIA, CIA, TPPA or FTA-ABS assay.

The RPR and VDRL non-treponemal tests belong to CPT 86592, and billing the wrong one is the most common denial trigger.

Medicare covers 86780 under NCD 210.10 for pregnant patients and high-risk adults, with Z11.3 as the preventive code that removes cost-sharing.

Billing 86780 and CPT 86592 on the same date triggers NCCI edit scrutiny, so check the current quarterly edit tables first.

Practice management software like Pabau links lab orders to the correct CPT codes, so miscoded claims get caught before submission.

CPT code 86780: Official descriptor and clinical overview

CPT code 86780 is the five-digit procedure code the American Medical Association publishes as “Antibody; Treponema pallidum”. It covers detection of antibodies specific to Treponema pallidum, the bacterium that causes syphilis, using treponemal immunoassays.

Many code lookups display “Qualitative or Semiquantitative Immunoassays” next to 86780. That is the title of the 86000-86804 category the code sits inside, not the descriptor for 86780 itself. The distinction matters on appeal, where a payer reads the official descriptor rather than the category heading.

Covered laboratory methodologies include enzyme immunoassay (EIA), chemiluminescent immunoassay (CIA), and Treponema pallidum particle agglutination (TPPA). The result is reported as reactive or non-reactive, so the code is billed once per test rather than once per titer value.

• Analyte: Treponema pallidum-specific IgG and/or IgM antibodies
• Methodologies covered: EIA, CIA, TPPA, fluorescent treponemal antibody absorption (FTA-ABS)
• Result type: Reactive / Non-reactive (qualitative) or semiquantitative titer
• Clinical uses: Confirmatory syphilis testing, reverse-sequence screening, prenatal panel, treatment monitoring when antibody status alone is needed
• Not covered: Non-treponemal tests (RPR, VDRL), culture, dark-field microscopy, titer quantification billed under separate codes

The code sits in the CPT Immunology subsection (80000 series) alongside related serology codes. It does not carry a global period and is billed per test occurrence, not per date-of-service interpretation.

CPT 86780 vs 86592: Treponemal vs non-treponemal tests

The most common coding error in syphilis serology is interchanging CPT code 86780 with 86592. They test different analytes with different clinical implications, and payers treat them as distinct services.

The CDC describes both a traditional algorithm (RPR first, treponemal confirmatory) and a reverse-sequence algorithm (treponemal EIA/CIA first, then RPR reflex). Which algorithm the laboratory runs decides which code is billed first, as the two pathways below show. Some payers still require the traditional sequence, so verify with each MAC or commercial plan before assuming reverse-sequence coverage.

Related STI screening codes billed alongside CPT code 86780

Syphilis serology rarely travels alone. Both prenatal panels and comprehensive STI panels routinely bundle CPT code 86780 with several other codes. Knowing the co-billing landscape prevents bundling denials and NCCI edit triggers.

The American College of Obstetricians and Gynecologists recommends syphilis screening at the first prenatal visit for every pregnant patient. Repeat testing in the third trimester applies in high-prevalence areas, or where risk factors continue.

Each test in the panel is separately reportable. NCCI edits do apply when 86780 and 86592 are billed together by the same provider on the same date. Check the current quarterly NCCI edit tables on the CMS coding and billing page before submitting both on one claim.

ICD-10 diagnosis codes that support CPT code 86780 claims

Payers require a supporting diagnosis code that justifies ordering the treponemal antibody test. The right ICD-10-CM code also decides whether the patient owes cost-sharing, or whether the visit qualifies for preventive coverage.

• Z11.3 (Encounter for screening for infections with a predominantly sexual mode of transmission): The primary preventive code. Use it when the test is ordered for screening in asymptomatic patients, routine prenatal screening included. It triggers Medicare and Medicaid preventive coverage with no patient cost-sharing.
• A53.9 (Syphilis, unspecified): Use when syphilis infection has been diagnosed but the stage is not specified. It signals a diagnostic rather than preventive encounter.
• A51.0 (Primary genital syphilis), A51.1 (Primary anal syphilis), A51.2 (Primary syphilis of other sites): Stage-specific codes for confirmed primary-stage syphilis.
• O98.11 (Syphilis complicating pregnancy, first trimester), O98.12 (second trimester), O98.13 (third trimester): Use for syphilis confirmed or suspected in a pregnant patient. Trimester specificity has to be right, because the wrong trimester is a leading denial trigger on obstetric claims.
• Z34.01 / Z34.11 / Z34.31 (Encounter for supervision of normal first/second/third trimester pregnancy): These are acceptable supporting codes. Use them when 86780 is part of a routine prenatal panel billed outside the global obstetric package.

Cross-check the CDC tool against your MAC’s local coverage determination before you finalize the claim. A code that satisfies one payer’s medical-necessity list can still fail another’s.

Documentation requirements for clean claims

Clean claim submission for CPT code 86780 requires five documentation elements to be in place before the claim leaves your billing system. Missing any one of them is enough for a CO-4 or CO-97 denial.

1. Clinical indication in the chart note: Document the reason for ordering the treponemal antibody test — prenatal visit, high-risk screening, reactive RPR reflex, or known exposure. The note must connect the order to the diagnosis code on the claim.
2. Methodology specified: The laboratory report or requisition should confirm EIA, CIA, TPPA, or FTA-ABS. If the report says “RPR” and you bill 86780, the claim will deny. Match the code to the methodology performed.
3. Laboratory NPI on the claim: CPT 86780 is a laboratory procedure code. The performing laboratory’s NPI must appear in Box 32 (CMS-1500) or the corresponding 837P loop (2420A). Billing under the ordering provider’s NPI alone is a common error in reference lab scenarios.
4. Place of service code: POS 81 (Independent Laboratory) for reference labs, or POS 11 (Office) if performed in-house with a CLIA-certified lab. Mismatched POS and modifier combinations trigger edits.
5. Modifier 90 for reference lab specimens: Append modifier 90 when a practice bills for a test performed at a reference lab. The performing lab also bills under its own NPI, and modifier 90 on the ordering provider’s claim distinguishes the two.

Build these five fields into the lab order template so a missing element surfaces at order entry rather than at billing. Practice management software like Pabau adds claims management that checks the code against the order before the claim goes out.

Medicare and Medicaid coverage for CPT code 86780

Medicare covers syphilis screening under National Coverage Determination (NCD) 210.10, titled Screening for Sexually Transmitted Infections (STIs) and High-Intensity Behavioral Counseling (HIBC). Two populations qualify: Pregnant beneficiaries in any trimester, and non-pregnant adults at increased risk for sexually transmitted infections.

Coverage databases list this policy as record 352, which is a database record ID rather than the NCD number. Quote 210.10 on an appeal. Coverage is also limited to the frequency the NCD specifies, and exceeding it without extra medical necessity documentation will deny the claim.

• Pregnant beneficiaries: Medicare covers syphilis screening at the first prenatal visit, and once in the third trimester for high-prevalence areas. Use Z11.3 as the primary diagnosis to trigger preventive benefit coverage with no patient cost-sharing.
• High-risk non-pregnant adults: Covered when the provider documents increased STI risk in the chart. The beneficiary must be a Medicare Part B enrollee. One screening per 12-month period is the standard frequency, and some MACs specify additional criteria.
• Noridian and MAC LCDs: Noridian Healthcare Solutions (Jurisdictions E and F) maintains a local coverage determination governing preventive STI screening that includes 86780. Check your MAC’s LCD for locally imposed frequency limits, or covered diagnoses beyond the NCD baseline.
• Medi-Cal Family PACT: California’s Family PACT program has issued billing policy updates affecting CPT code 86780. Verify the current DHCS policy directly before billing treponemal testing under Family PACT, because these notices are superseded often.

STI screening codes sit where federal NCD rules, MAC local coverage determinations, and state Medicaid policies all meet. Each of the three changes on its own schedule, so a coverage rule you verified last quarter may no longer hold.

2025-2026 fee schedule: Medicare reimbursement for CPT code 86780

Medicare reimbursement for CPT code 86780 is set by the Clinical Laboratory Fee Schedule (CLFS), not the Physician Fee Schedule. Laboratory codes in the 80000 series are priced under the CLFS, which CMS updates annually. Verify the current rate through the CMS fee schedule lookup for the applicable payment year.

Commercial contracted rates for CPT code 86780 usually sit above the Medicare CLFS allowable, though the spread varies by payer and region. Because 86780 is priced under the CLFS rather than the physician fee schedule, the usual conversion-factor math does not apply to it.

Common denial reasons for CPT code 86780 and how to fix them

The denial patterns below come from NCCI edit logic and standard payer audit criteria as they apply to syphilis serology. Each one has a specific corrective action, so match the remark code on the remittance to the row before you resubmit.

Every row above maps to a remark code. The full denial codes reference explains the CARC framework and the appeal workflow behind each one. Reading the remittance systematically, rather than only checking the dollar amount, catches a recurring 86780 pattern early. Otherwise the same error repeats across a whole billing period.

Prenatal panel billing: Using CPT code 86780 in obstetric care

ACOG recommends syphilis serology at the first prenatal visit for every patient. A repeat screen at 28 to 32 weeks applies in high-prevalence areas. The billing question that follows is whether 86780 sits inside the obstetric global package or outside it.

• Global package vs separately reportable: Whether CPT code 86780 falls inside a payer’s prenatal global package depends on that payer’s obstetric global definition. Medicare does not include laboratory codes in the global obstetric package, so the test is separately billable. Many commercial payers follow the same rule, but confirm each policy before unbundling lab codes.
• Diagnosis code selection by trimester: For a normal pregnancy without confirmed syphilis, use Z34.01 / Z34.11 / Z34.31. Add Z11.3 as the secondary code to capture the screening intent. If syphilis is confirmed, use the appropriate O98.1x code with correct trimester specificity.
• Billing for in-office vs reference lab specimens: The practice may bill 86780 with modifier 90 when it collects the specimen and sends it out. The reference lab bills separately under its own NPI. Both claims must carry matching specimen dates, or payers will query the discrepancy.
• Third-trimester repeat screen: A second screening in the same pregnancy requires documented clinical rationale, such as a high-prevalence area or ongoing risk factors. Use a new Z11.3 code with the correct trimester encounter code. Without that documentation, the repeat screen may be denied for exceeding the frequency limit.

Cross-referencing bundling notes against the AAPC CPT code lookup while you design the order set is a one-time step that prevents repeat denials. Do it once per panel, not once per claim.

How claims management software keeps 86780 matched to the test performed

Today the chain breaks in the handoff. The lab report names the methodology, the biller reads the requisition, and the CPT code is chosen from memory. When the requisition says syphilis screen and the report says RPR, 86780 goes out on a claim that 86592 should have carried.

Pabau closes that loop by holding the order, the result and the code on one patient record. The lab order carries its CPT code from the moment it is raised, so the biller is confirming a code rather than choosing one.

The same record carries the diagnosis code, so a prenatal panel leaves with Z11.3 attached rather than picked up later in a denial review. Claim status returns to the same screen, which means a CO-97 bundling edit on 86780 surfaces while the encounter is still fresh.

Manage lab orders and claims in one place

Pabau links your lab orders to CPT codes, tracks claim status, and flags common denial triggers before submission. See how practices billing STI and prenatal panels use Pabau to reduce rework.

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Conclusion

Two decisions carry almost all the denial risk on this code. The first is treponemal against non-treponemal: 86780 or 86592, read off the lab report rather than the requisition. The second is the diagnosis code, where Z11.3 buys preventive coverage and a vague A53.9 rarely does.

Settle both at order entry and the rest of the claim mostly looks after itself. Settle them at appeal and you are paying twice for the same test. Frequency limits and MAC variations matter, but they are second-order next to those two.

Book a demo to see how Pabau keeps the lab order, the result and the CPT code on one record.

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