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Onychomycosis Testing
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Policy governing laboratory testing methods for diagnosis and confirmation of onychomycosis (nail fungal infection) and coverage determinations for those tests for Blue Cross Blue Shield of Louisiana members.
No material clinical or coverage changes in this revision.
Coverage Criteria for Onychomycosis Testing
inv-01: Initial diagnostic testing — covered
Covered when criteria are met
inv-02: NAAT — covered only after failed therapy
Covered when criteria are met
NAAT examples include PCR, PCR-RFLP, and next-generation sequencing for organisms listed in Note 1 (eg, Candida spp., Aspergillus spp., Trichophyton spp., Fusarium spp.).
inv-03: Not covered — screening/diagnosis and specific modalities
Not covered for stated uses
inv-04: Laboratory confirmation recommended prior to treatment
Guidelines summarized from multiple professional societies recommend laboratory confirmation in most cases before initiating treatment. Key points from guideline sources:
Sources: British Association of Dermatologists (BAD), American Academy of Family Physicians (AAFP), Journal of Drugs in Dermatology (JDD)
Sources: BAD, AAFP, JDD
Sources: BAD, AAFP
inv-05: Referenced coverage criteria edits (revision-history summaries referencing coverage criteria changes)
Revision-history summaries referencing coverage criteria changes
Referenced in 09/01/2025 revision summary.
Referenced in 10/01/2024 and 06/01/2023 revision notes.
Per the policy's indications and limitations, nucleic acid amplification testing (NAAT) to screen for, diagnose, or confirm onychomycosis does not meet coverage criteria. NAAT is only supported under the policy when used after antifungal therapy has failed to resolve infection (separate coverage criterion).
The policy states that attenuated total-reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and testing for fungal-derived sterols (e.g., ergosterol) do not meet coverage criteria for screening, diagnosis, or confirmation of onychomycosis due to insufficient published evidence supporting clinical benefit.
The British Association of Dermatologists notes that while PCR/real-time PCR increases detection rates and shortens turnaround time, PCR may detect nonpathogenic or dead fungus, which can limit its utility for identifying the true pathogen and interpreting positive results in clinical context.
The revision history summarizes literature reviews and wording edits across multiple review dates; these notes document clarifications to coverage language and additions (for example, adding NAAT in a limited post‑treatment-failure indication) but do not themselves list additional explicit exclusions beyond those in the main coverage section.
Overall coverage determinations characterize NAAT for routine screening, diagnosis, or confirmation, ATR-FTIR spectroscopy, and fungal-derived sterol testing (eg, ergosterol) as not meeting coverage criteria for those indications under this policy.
The Journal of Drugs in Dermatology review recognizes that PCR techniques can be useful for confirming diagnosis and species identification but concluded they were not cost-effective enough for general use, supporting a limited role for PCR/NAAT outside routine first-line testing.
Revision-history entries indicate literature reviews and editorial wording changes were performed on multiple dates; those summaries state that reviews did not necessitate changes to coverage criteria in several updates and therefore do not present additional explicit 'not medically necessary' statements in the noted chunks.
Provider Actions, Documentation, and Denial Risk
NAAT covered only after treatment failure
NAAT (nucleic acid amplification testing) is covered only for individuals with onychomycosis when antifungal therapy has failed to resolve the infection; NAAT submitted to screen for, diagnose, or confirm onychomycosis does not meet coverage criteria and may be denied.
- NAAT is allowed after failed therapy for the listed organisms in Note 1 (e.g., Candida spp., Aspergillus spp., Trichophyton spp., Fusarium spp., etc.).
Procedure codes referenced (reference only)
Procedure codes potentially applicable to onychomycosis diagnostic testing are provided for reference; payer-specific prior authorization requirements are not specified in this policy section.
No prior authorization specified in policy text
This document does not state any payer-specific prior authorization requirement for onychomycosis testing; revision history and coverage criteria in the cited chunks do not specify prior authorization mechanics.
- Revision history notes coverage changes but does not list prior authorization requirements.
Preferred diagnostic sequence: traditional tests first
Use traditional diagnostic methods (KOH microscopy, fungal culture, PAS histology) as first-line diagnostics; NAAT is positioned as a subsequent test when antifungal therapy has failed or resistance is suspected.
- KOH preparation, fungal culture, and PAS-stained histology meet coverage criteria for individuals with signs of onychomycosis.
- PCR/NAAT can improve species detection and turnaround time but is reserved for post-treatment failure per coverage criteria.
Empiric terbinafine may be considered when testing not feasible
If diagnostic testing is not feasible or is cost-prohibitive, empiric oral terbinafine may be considered per AAFP guidance; however, testing is generally recommended prior to initiating systemic therapy.
- AAFP states diagnostic testing is generally recommended but that empiric terbinafine can be considered when testing is cost prohibitive.
No formal step therapy or sequencing specified
No step therapy requirements or mandated sequencing of tests/treatments are specified in these policy chunks.
- The document discusses preferred diagnostic approaches but does not impose formal step-therapy pathways.
Document KOH, culture, or PAS results for initial testing
For initial diagnostic testing, document signs of onychomycosis and results supporting one or more covered methods: direct microscopy with KOH, fungal culture of desquamated subungual material, or fungal stain (e.g., PAS) of nail clippings.
- Record clinical signs that prompted testing and the specific laboratory method used (KOH, culture, PAS).
- KOH, culture, or PAS results should be included in the medical record to meet coverage criteria for initial diagnostics.
Document prior treatment failure before NAAT
When NAAT is performed to meet coverage after antifungal treatment failure, document prior antifungal therapy and evidence that the infection persisted despite treatment.
- Include type(s) of antifungal therapy, duration, and documentation of treatment failure before NAAT is considered covered.
Specimen collection and documentation requirements
Collect and document nail specimens from discolored, dystrophic, or brittle areas; clean the nail with 70% isopropyl alcohol and obtain subungual debris and multiple nail clippings (typically 8–10) as recommended in guidelines.
- Specimens should be taken from the most proximal area of onycholysis when present; trimming the nail plate may be necessary to access this area.
- Document the collection method and specimen source in the medical record to support diagnostic testing results.
Supporting references and vendor links for documentation
Use the policy's evidence-based references and listed laboratory vendor/test URLs to support diagnostic methods and documentation; these sources may be cited when providing test rationale but the policy does not prescribe a specific documentation form.
- References include guideline statements (BAD, AAFP) and vendor/test resources (e.g., LabCorp, MicroGenDX, EuroImmun) that can corroborate chosen diagnostic methods.
NAAT excluded for screening/diagnosis/confirmation
NAAT submitted to screen for, diagnose, or confirm onychomycosis does not meet coverage criteria and may be denied when billed for those purposes.
- Note 1 lists the organisms for which NAAT is allowable only after treatment failure; NAAT for routine diagnosis/screening remains excluded.
ATR-FTIR testing excluded — denial risk
Attenuated total-reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to screen, diagnose, or confirm onychomycosis does not meet coverage criteria and may be denied.
- ATR-FTIR is listed among modalities that lack sufficient published literature to meet coverage criteria.
Ergosterol/sterol testing excluded
Testing for fungal-derived sterols (for example, ergosterol) does not meet coverage criteria and may be denied when submitted to screen, diagnose, or confirm onychomycosis.
- Mass spectrometry assays for ergosterol are referenced in the literature but are characterized in the policy as not meeting coverage criteria.
Government coverage takes precedence when applicable
If there is a conflict between this policy and an applicable government coverage determination (e.g., LCD/NCD or state Medicaid), the government policy takes precedence and will be used for the member's coverage determination.
- Providers should consult the Medicare Coverage Database or relevant state Medicaid resources for the most current government policies.
No explicit denial triggers specified in these sections
The policy's revision history and cited chunks do not list explicit authorization denial triggers or formal mechanics for denials; the document states exclusions and coverage criteria but does not enumerate specific denial workflows.
- Absence of explicit denial triggers in revision notes means providers should rely on stated coverage criteria and exclusions when anticipating claim outcomes.
Procedure and Billing Codes
| 82542 | Column chromatography, includes mass spectrometry, if performed (eg, HPLC, LC, LC/MS, LC/MS-MS, GC, GC/MS-MS, GC/MS, HPLC/MS), non-drug analyte(s) not elsewhere specified, qualitative or quantitative, each specimen |
| 87101 | Culture, fungi (mold or yeast) isolation, with presumptive identification of isolates; skin, hair, or nail |
| 87149 | Culture, typing; identification by nucleic acid (DNA or RNA) probe, direct probe technique, per culture or isolate, each organism probed |
| 87150 | Culture, typing; identification by nucleic acid (DNA or RNA) probe, amplified probe technique, per culture or isolate, each organism probed |
| 87153 | Culture, typing; identification by nucleic acid sequencing method, each isolate (eg, sequencing of the 16S rRNA gene) |
| 87205 | Smear, primary source with interpretation; Gram or Giemsa stain for bacteria, fungi, or cell types |
| 87206 | Smear, primary source with interpretation; fluorescent and/or acid fast stain for bacteria, fungi, parasites, viruses or cell types |
| 87220 | Tissue examination by KOH slide of samples from skin, hair, or nails for fungi or ectoparasite |
| 87480 | Infectious agent detection by nucleic acid (DNA or RNA); Candida species, direct probe technique |
| 87481 | Infectious agent detection by nucleic acid (DNA or RNA); Candida species, amplified probe technique |
Background on Onychomycosis and Diagnostic Methods
Onychomycosis is a fungal infection of the nail most commonly caused by dermatophytes (for example, Trichophyton species), but may also be due to yeasts and nondermatophyte molds. Toenails are affected more often than fingernails, and laboratory confirmation is recommended because clinical appearance alone is insufficient for definitive diagnosis.
Definitions and Abbreviations
Policy Revision History
Clinical Advisory Board meeting held; policy review and approval on 03/18/2026 documented in revision history.
Background, guidelines, and evidence references were updated; wording edit added 'signs of' to CC1 to clarify diagnostic criteria wording.
Added new CC2 to allow NAAT testing when treatment has been ineffective and antifungal resistance is suspected (coverage criteria updated to include NAAT in that circumstance).
Clarified that for individuals with onychomycosis whose antifungal therapy has failed, nucleic acid amplification testing (NAAT) meets coverage criteria and standardized the NAAT initialism in criteria text.
Initial policy implementation recorded.
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