CurrentPremera BluecrossPolicy 15.01.022

15.01.022 Nerve Fiber Density Testing

Policy describing clinical background, indications, coding, guidelines, and evidence regarding skin biopsy-based nerve fiber density testing (PGP 9.5 IENFD/ENFD and sweat gland nerve fiber density) for evaluation of small fiber and autonomic neuropathies. Contains statement that measurement of sweat gland nerve fiber density is not reimbursable and lists CPT codes used for pathology staining/analysis.

Policy Summary

PayerPremera Bluecross

Policy15.01.022 Nerve Fiber Density Testing

Policy CodePolicy 15.01.022

Change TypeAdded; Coding revised

Effective DateFeb 6, 2026

Next Review DateN/A

Key ActionProviders should document clinical signs of small fiber dysfunction when ordering skin biopsy / IENFD testing to support medical necessity and follow updated coding (88342 removed).

SourceLink

POLICY UPDATE CHANGES

New policy approved October 14, 2025 and added to Routine Test Management, effective for dates of service on or after 2026-02-06 after 90-day notification.

Coding update on 2026-02-06 removed CPT code 88342 from the policy.

1Explicit Non-reimbursable Indication

2Society recommendations cited

1Coding changes

1Routine Test Management addition

Coverage Summary

This policy covers skin biopsy–based nerve fiber density testing (PGP 9.5 IENFD/ENFD and sweat gland nerve fiber density) for evaluation of small fiber and autonomic neuropathies, including clinical background, indications, coding, guideline summaries, and evidence. Coverage stance is mixed. Effective date and last review: 2026-02-06. The policy explicitly states that measurement of sweat gland nerve fiber density is not reimbursable (SGNFD). The policy was created and added to Routine Test Management (new policy approved October 14, 2025; added to Routine Test Management and effective for dates of service on or after February 6, 2026 following 90‑day provider notification).

Nerve Fiber Density Testing - Policy 15.01.022

15.01.022

Effective for dates of service on or after Feb. 6, 2026

Last Revised: Feb. 6, 2026

CURRENT

mixed (policy includes reimbursable guidance for IENFD/ENFD; explicit non-reimbursable statement for sweat gland nerve fiber density)

Medical-Necessity Criteria

Indications / Reimbursement Statement

Measurement of sweat gland nerve fiber density is not reimbursable.

Clinical utility and recommended uses

Guidance and recommendations from specialty societies and literature regarding skin biopsy / IENFD:

Skin biopsy with appropriate histological processing and image analysis should be performed in patients with clinical signs of small fiber dysfunction to determine intraepidermal nerve fiber density (NeuPSIG recommendation; level B).

Measurement of intraepidermal nerve fiber density may be used in follow up and to detect a treatment response in diabetic patients with small fiber neuropathy (NeuPSIG; level C).

IENFD has been used to diagnose peripheral neuropathies (painful or not), but additional research is needed to validate IENFD specifically as a diagnostic biomarker for pain conditions and for conditions such as fibromyalgia.

Coding

Pathology / Immunohistochemistry and Morphometric Analysis Codes listedCPT

88341	Immunohistochemistry or immunocytochemistry, per specimen; each additional single antibody stain procedure (List separately in addition to code for primary procedure).
88356	Morphometric analysis; nerve

Removed CPT codes (per history)CPT

88342

Removed from coding (policy history note: Removed CPT code 88342 on 02/06/26).

Operational coding update: CPT code 88342 was removed on 2026-02-06. Providers must not bill CPT 88342 under this policy and should use the current authorized CPT coding (e.g., 88341, 88356) consistent with the updated policy.

Provider Actions

Billing Rule

Sweat gland nerve fiber density measurement not reimbursable

Claims for measurement of sweat gland nerve fiber density (SGNFD/SGNF/SGII) are not reimbursable under this policy. Do not submit charges expecting reimbursement for SGNFD, SGNF, or SGII testing.

Do not bill for SGNFD/SGNF/SGII expecting reimbursement.

Documentation Required

Document clinical signs of small fiber dysfunction

When ordering skin biopsy/IENFD testing, document the patient’s clinical signs of small fiber dysfunction to support medical necessity in accordance with NeuPSIG and other specialty guidance.

Document objective clinical signs of small fiber dysfunction when ordering IENFD testing per NeuPSIG guidance.

Background

Background: Skin biopsy uses a 3 mm punch specimen stained with the PGP 9.5 antibody to visualize axons and measure epidermal / intraepidermal nerve fiber density (ENFD/IENFD) to assess small fiber neuropathy. Clinical contexts for which IENFD/ENFD testing has been applied include diabetes, hypothyroidism, Fabry disease, sarcoidosis, fibromyalgia, Parkinson disease, Charcot–Marie–Tooth disease type 1A (CMT1A), Ehlers–Danlos syndrome (EDS), Friedreich’s ataxia (FRDA), erythromelalgia, and familial amyloid polyneuropathy. Applications include assessment of both sensory small fiber neuropathy and autonomic (sudomotor) innervation. Proprietary commercial ENFD/ENFD test kits are available from vendors (e.g., Therapath, BakoDx, Corinthian) and many laboratories perform laboratory‑developed tests (LDTs) that are validated and performed under CLIA; these LDTs are not FDA‑cleared/approved.

Epidermal / Intraepidermal nerve fiber density measured on skin biopsy stained with PGP 9.5.

Sweat gland nerve fiber density / sweat gland innervation index - measures of sudomotor innervation from skin biopsy specimens. Measurement of sweat gland nerve fiber density is not reimbursable.

Protein gene product 9.5 (PGP 9.5), an antibody marker used to stain all axons in skin biopsy specimens.

Intraepidermal nerve fiber density (IENFD), measured via skin biopsy and histological analysis to assess small fiber neuropathy.

Evidence & Guidelines

Evidence and guidance: The policy cites guideline recommendations and selected studies, including NeuPSIG recommendations on skin biopsy (level B for diagnosis with clinical signs of small fiber dysfunction; level C for follow‑up in diabetic small fiber neuropathy) and representative diagnostic accuracy and normative studies referenced in the evidence review.

Citation / Label	Key finding or value
England et al., 2009b - sensitivity range	Sensitivity of decreased IENF density for polyneuropathy ranged from 45% to 90%; specificity 95% to 97%.
Collongues et al., 2018 - normative formula	5th percentile IENFD = 7.6156 - 0.0769 x age + 1.5506 x gender (woman=1; man=0).
Piscosquito et al., 2021 - interfiber distance	Interfiber distance >350 µm differentiates patients from controls (AUC=0.85; sensitivity 74%; specificity 94%).
NeuPSIG recommendation	Skin biopsy recommended for patients with clinical signs of small fiber dysfunction to determine IENFD (level B); measurement may be used for follow-up and to detect treatment response in diabetic small fiber neuropathy (level C).
Research gap	Additional research is needed to validate IENFD specifically as a diagnostic biomarker for pain conditions (e.g., fibromyalgia).

Revision History

2025-10-14policy_created

New policy approved October 14, 2025 and added to Routine Test Management; effective for dates of service on or after 2026-02-06 following 90-day provider notification.

2026-02-06coding_updateLatest

Coding update removed CPT code 88342 from the policy.