CurrentAetnaPolicy 0774

Nerve Fiber Density Measurement

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This policy governs when measurement of intra-epidermal nerve fiber density (IENFD) by skin biopsy and related sweat-gland nerve fiber assessments are considered medically necessary, experimental/investigational, and which codes/diagnoses relate to coverage for Aetna members.

Policy Summary

PayerAetna

PolicyNerve Fiber Density Measurement

Policy CodePolicy 0774

Change TypeNo material change

Effective DateJan 9, 2009

Last ReviewOct 11, 2023

Next Review DateAug 22, 2024

Key ActionObtain and document prior noninvasive or electrodiagnostic testing (NCVS, QST, EMG/nerve conduction) and ensure biopsy site and standardized technique are specified when requesting coverage for IENFD testing.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

1Medically necessary criteria groups

9+Experimental/investigational indications (examples)

~20Document chunks

88%reduced IENFD in Scherens et al.

Coverage and Medical Necessity Criteria

Evidence summaries (no formal criteria provided here)

Evidence summaries (no formal criteria provided here). The following summarizes clinical studies, guidelines, and systematic reviews relevant to nerve fiber density measurement (intra-epidermal and sweat gland) and its diagnostic or research applications.

Small studies and comparative research have generally shown that reduced intra-epidermal nerve fiber density (IENFD) correlates with clinical and functional measures of small‑fiber neuropathy (SFN) and may be more sensitive than nerve conduction studies for detecting SFN (Teoh et al. 2008; Scherens et al. 2009; Lauria et al. 2005).

Skin biopsy with quantification of IENFD (3‑mm punch biopsy at distal leg, immunohistochemistry with anti‑PGP9.5, analysis of multiple sections) is supported by guideline-level recommendations as a validated technique for diagnosis of distal small‑fiber sensory polyneuropathy (EFNS/PNS, Lauria et al. 2005; England et al. 2009).

Skin biopsy techniques and reporting vary across studies; standardized methods (specific fixatives, sectioning, staining, and stereologic or validated morphometric analysis) improve reproducibility and diagnostic performance (Lauria et al. 2005; Gibbons et al. 2009, 2010; EFNS/PNS 2010).

Noninvasive functional tests (quantitative sensory testing [QST], stimulated skin wrinkling, autonomic testing) have variable sensitivity and specificity relative to IENFD; some modalities (e.g., stimulated skin wrinkling) may be nearly as sensitive as IENFD in certain settings and are useful when biopsy is unavailable (Teoh et al. 2008; Scherens et al. 2009).

Commercial (standard) biopsy processing that lacks stereologic quantitative analysis may miss subtle or localized denervation and may not correlate well with functional testing in some conditions (Kharkar et al. 2012).

Stereologic and automated morphometric approaches to measuring sweat gland (sudomotor) innervation show promise and may be more sensitive than descriptive semi‑quantitative methods; however, methods are not standardized and descriptive/semi‑quantitative approaches have poor reliability (Gibbons et al. 2009, 2010; EFNS/PNS 2010; Provitera et al. 2014; Liu et al. 2015).

Evidence is heterogeneous across disease states: studies report reduced IENFD or altered sudomotor innervation in conditions including fibromyalgia, POTS, REM sleep behavior disorder, hereditary and iatrogenic transthyretin (TTR) amyloidosis, Fabry disease, Ehlers‑Danlos syndromes, multiple system atrophy, CRPS‑I, and idiopathic small‑fiber neuropathy, but clinical implications vary and diagnostic utility is not established for many indications (multiple studies cited: Caro & Winter 2014; Kosmidis et al. 2014; Haensch et al. 2014; Schrempf et al. 2016; Masuda et al. 2017; Chao et al. 2014; Provitera et al. 2014; Kharkar et al. 2012; Cazzato et al. 2016; Haroutounian et al. 2021; Vecchio et al. 2020).

Use as a research endpoint and potential biomarker: IENFD and stereologic sweat gland measures have been used as outcomes in small clinical studies and may detect change over time or with intervention in research settings, but routine clinical use for monitoring disease progression or treatment response is not established (Jacobs & Cheng 2011; Liu et al. 2015; Masuda et al. 2017).

Limitations and diagnostic performance: sensitivity and specificity vary by condition and study; for example, in uncertain Fabry disease cohorts, IENFD and QST could not reliably distinguish affected from unaffected individuals (van der Tol et al. 2016). In endometrial assessment, PGP9.5‑positive nerve fibers in eutopic endometrium did not reliably distinguish endometriosis (Liutkeviciene et al. 2019).

Systematic reviews and guideline authors note heterogeneity in diagnostic criteria for idiopathic SFN and call for standardized, evidence‑based diagnostic criteria and further studies to validate methods and clinical utility (Haroutounian et al. 2021; EFNS/PNS 2010).

Procedure and Diagnosis Codes

Procedure and related CPT codesCPT

10004	Fine needle aspiration biopsy, without imaging guidance; each additional lesion
11104	Punch biopsy of skin (including simple closure, when performed); single lesion
11105	Punch biopsy of skin (including simple closure, when performed); each separate/additional lesion
88305	Level IV Surgical pathology, gross and microscopic examination, nerve, biopsy
88314	Special stain including intrepretation and report; histochemical stain on frozen tissue block
88341	Immunohistochemistry or immunocytochemistry, per specimen
88342	Immunohistochemistry or immunocytochemistry, per specimen
88343	Immunohistochemistry or immunocytochemistry, per specimen
88344	Immunohistochemistry or immunocytochemistry, per specimen
88356	Morphometric analysis; nerve

1–10 of 34

1/4

ICD-10 codes (covered if selection criteria met; many listed as not covered for listed indications)ICD-10

G60.8	Other hereditary and idiopathic neuropathies
E00.0 - E00.9	Congenital iodine-deficiency syndrome
E03.0 - E03.1	Other hypothyroidism
E08.40 - E08.49	Diabetes mellitus due to underlying condition with neurological complications
E09.40 - E09.49	Drug or chemical induced diabetes mellitus with neurological complications
E10.40 - E10.49	Type 1 diabetes mellitus with neurological complications
E11.40 - E11.49	Type 2 diabetes mellitus with neurological complications
E13.40 - E13.49	Other specified diabetes mellitus with neurological complications
E75.21	Fabry (-Anderson) disease
E85.0 - E85.9	Amyloidosis [hereditary transthyretin (TTR) amyloidosis]

1–10 of 29

1/3

Procedure codes referenced implicitlymixed

not listed

No explicit CPT/ICD codes provided in this document segment

inv-16: Ankle IENFD threshold for early diabetic neuropathy — < 10 mm (sensitivity 72.4%, specificity 76.2%)

Ankle IENFD threshold< 10 mm

Sensitivity72.4%

Specificity76.2%

ContextThreshold derived from comparison of diabetic subjects vs controls for early diabetic neuropathy (Umapathi et al., ankle IENFD)

Prior Authorization, Documentation, and Billing Guidance

Denial Risk

Denial Triggers for IENFD Testing

Denial triggers for IENFD testing: Failure to meet all listed medical necessity criteria — e.g., absence of painful sensory neuropathy, presence of a disorder known to predispose to painful neuropathy (such as diabetic neuropathy, toxic neuropathy, HIV neuropathy, celiac neuropathy, or inherited neuropathy), clinical or exam findings consistent with large‑fiber neuropathy (reduced/absent reflexes, impaired proprioception/vibration), or abnormal needle EMG/nerve conduction studies — may lead to claim denial for IENFD testing.

Denial trigger: Missing documentation of painful sensory neuropathy
Denial trigger: History of a predisposing disorder (diabetes, toxic exposure, HIV, celiac disease, inherited neuropathy)
Denial trigger: Clinical or exam evidence of large‑fiber neuropathy (reduced reflexes, impaired proprioception/vibration)
Denial trigger: Abnormal EMG or nerve conduction studies indicating large‑fiber involvement

Note

Risk from Non‑Specialized Processing and Method Limitations

Risk from non‑specialized processing: Standard commercial processing without stereologic quantitative analysis may miss focal or partial denervation and subtle ultramicroscopic changes; descriptive or semi‑quantitative approaches for sweat gland innervation have poor inter‑ and intra‑observer reliability and are discouraged. Specimen handling and use of validated quantitative methods (eg, stereologic unbiased techniques, appropriate fixation and anti‑PGP9.5 staining, and morphometric analysis) should be documented to support test validity.

Risk: Commercial processing may not use stereologic quantitative analysis and can miss localized denervation
Risk: Descriptive semi‑quantitative sweat gland innervation methods show poor reliability — avoid for diagnostic quantification
Suggested documentation: biopsy site, fixation method, stains/markers used (eg, PGP 9.5), number of sections quantified, and whether stereologic/morphometric analysis was performed

Documentation Required

Provider Actions / Operational Note

Provider actions: None explicit in this section beyond usual documentation and prior‑authorization guidance elsewhere in the policy. Providers should follow the policy’s medical necessity criteria, include required clinical and technical documentation when submitting claims (clinical presentation, prior noninvasive test results, biopsy site and processing details), and be aware that prior authorization requirements, if applicable, are addressed separately.

Action: Ensure all medical necessity criteria are documented in the record
Action: Include results of noninvasive testing (NCVS, QST, stimulated skin wrinkling) when available to support indication
Action: Specify biopsy site(s) and laboratory methods (fixation, stains, number of sections, morphometric techniques) in the pathology report
Note: Prior authorization requirements are not specified in this section; check payer prior authorization rules

Definitions and Terminology

inv-34: Intra-epidermal nerve fiber density (IENFD) — Quantification of small nerve fibers in the epidermis from a punch skin biopsy specimen

DefinitionQuantification of small nerve fibers in the epidermis from a punch skin biopsy specimen

Specimen3-mm punch skin biopsy, thin sections stained and examined by pathologist

PurposeObjective diagnostic test to detect reduced intraepidermal nerve fiber density for diagnosis of small‑fiber neuropathy (SFN)

MarkerTypically uses pan-axonal marker PGP9.5 for immunohistochemical staining

inv-35: Small-fiber neuropathy (SFN) — Peripheral nerve disease affecting small diameter fibers, characterized by burning pain and altered temperature sensation

DefinitionPeripheral nerve disease affecting small diameter myelinated and unmyelinated fibers

Clinical featuresPainful burning sensations, reduced pain and temperature perception, often with normal standard electrophysiologic tests

CausesMay be idiopathic or secondary to diabetes, infections, toxins, genetic disorders, or autoimmune disease

inv-36: IENFD / ENFD — Intraepidermal (or epidermal) nerve fiber density measured from skin punch biopsy sections, typically quantified per linear mm using PGP9.5

TermIENFD / ENFD = intraepidermal (or epidermal) nerve fiber density measured from skin punch biopsy sections

UnitsReported as fibers per linear millimeter (fibers/mm)

TechniqueQuantified per linear mm using PGP9.5 immunostaining on recommended sections (e.g., at least three 50-µm sections)

inv-37: SGNFD — Sweat gland nerve fiber density: quantitative assessment of nerve fibers innervating sweat glands for autonomic evaluation

DefinitionSGNFD = sweat gland nerve fiber density; quantitative assessment of nerve fibers innervating sweat glands for autonomic evaluation

CorrelationSGNFD at distal leg correlates with neuropathy severity and symptoms of reduced sweat production

MethodsManual, automated, and stereologic techniques described; stereologic unbiased methods favored for accuracy

inv-38: IENFD — Intra-epidermal nerve fiber density: quantification of small sensory nerve fibers in the epidermis, typically measured by PGP9.5 staining

DefinitionIENFD = quantification of small sensory nerve fibers in the epidermis, typically measured by PGP9.5 staining and reported as fibers/mm

UseDetects small-fiber damage not seen on nerve conduction studies; used in diagnosis of SFN and assessment of autonomic involvement

ReportingCompared to age- and sex-matched normative reference values for interpretation

inv-39: Sudomotor nerve density / SGII — Measurement of sweat gland innervation often reported as SGII or total nerve length per gland volume

DefinitionSudomotor nerve density / SGII = measurement of sweat gland innervation often reported as sweat gland innervation index (SGII) or total nerve length per gland volume

MarkersMeasured using markers such as PGP9.5, VIP, or tyrosine hydroxylase (TH); VIP may be more sensitive in diabetes

Technical noteBecause sweat glands are 3‑D structures, stereologic or automated morphometric techniques are often required

inv-40: IENFD — Quantitative measure of small sensory nerve fibers in epidermis used to assess small‑fiber neuropathy

DefinitionIENFD = quantitative measure of small sensory nerve fibers in epidermis used to assess small‑fiber neuropathy

Clinical relevanceReduced IENFD observed in hereditary TTR amyloidosis and other conditions; correlates with clinical neuropathy measures

MeasurementReported as fibers per mm from distal leg, thigh, or other recommended biopsy sites

inv-41: PGP9.5-positive nerve fibers — Immunohistochemically identified nerve fibers using anti‑PGP9.5 marker (context: eutopic endometrium)

DefinitionPGP9.5-positive nerve fibers = nerve fibers identified immunohistochemically using anti‑PGP9.5 marker

ContextDetection of PGP9.5-positive fibers in eutopic endometrium was not sufficiently specific or sensitive to reliably diagnose endometriosis (Liutkeviciene et al., 2019)

ReportingReported as nerve fiber density per mm2 or presence/absence in tissue samples

Background and Rationale

Intra‑epidermal nerve fiber density (IENFD) testing by skin punch biopsy identifies and quantifies small sensory nerve fibers in the epidermis and is used to diagnose small‑fiber neuropathy (SFN). The policy states that IENFD measurement is medically necessary for diagnosis when all required clinical criteria are met (painful sensory neuropathy, no history of a disorder predisposing to painful neuropathy, absence of large‑fiber findings on exam, and normal needle EMG/nerve conduction studies). Skin punch biopsy with standardized fixation and PGP9.5 immunostaining and quantitative reporting (fibers/mm compared with age‑ and sex‑matched normative values) is the accepted method described in the policy background.

Policy History and Review Dates

2023-10-11policy_reviewLatest

Policy last reviewed on 10/11/2023; content retained in current version.

2009-01-09effective_date

Policy became effective on 01/09/2009.

2024-08-22next_review

Next scheduled review date listed as 08/22/2024.

Policy Summary

PayerAetna

PolicyNerve Fiber Density Measurement

Policy CodePolicy 0774

Change TypeNo material change

Effective DateJan 9, 2009

Last ReviewOct 11, 2023

Next Review DateAug 22, 2024

SourceLink

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Nerve Fiber Density Measurement

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Sign up for Aetna Policy 0774 alerts

Get alerted when Policy 0774 changes without checking for updates manually.

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Coverage and Medical Necessity Criteria

Evidence summaries (no formal criteria provided here)

Procedure and Diagnosis Codes

Procedure and related CPT codesCPT

10004	Fine needle aspiration biopsy, without imaging guidance; each additional lesion
11104	Punch biopsy of skin (including simple closure, when performed); single lesion
11105	Punch biopsy of skin (including simple closure, when performed); each separate/additional lesion
88305	Level IV Surgical pathology, gross and microscopic examination, nerve, biopsy
88314	Special stain including intrepretation and report; histochemical stain on frozen tissue block
88341	Immunohistochemistry or immunocytochemistry, per specimen
88342	Immunohistochemistry or immunocytochemistry, per specimen
88343	Immunohistochemistry or immunocytochemistry, per specimen
88344	Immunohistochemistry or immunocytochemistry, per specimen
88356	Morphometric analysis; nerve

1–10 of 34

1/4

ICD-10 codes (covered if selection criteria met; many listed as not covered for listed indications)ICD-10

G60.8	Other hereditary and idiopathic neuropathies
E00.0 - E00.9	Congenital iodine-deficiency syndrome
E03.0 - E03.1	Other hypothyroidism
E08.40 - E08.49	Diabetes mellitus due to underlying condition with neurological complications
E09.40 - E09.49	Drug or chemical induced diabetes mellitus with neurological complications
E10.40 - E10.49	Type 1 diabetes mellitus with neurological complications
E11.40 - E11.49	Type 2 diabetes mellitus with neurological complications
E13.40 - E13.49	Other specified diabetes mellitus with neurological complications
E75.21	Fabry (-Anderson) disease
E85.0 - E85.9	Amyloidosis [hereditary transthyretin (TTR) amyloidosis]

1–10 of 29

1/3

Procedure codes referenced implicitlymixed

not listed

No explicit CPT/ICD codes provided in this document segment

inv-16: Ankle IENFD threshold for early diabetic neuropathy — < 10 mm (sensitivity 72.4%, specificity 76.2%)

Ankle IENFD threshold< 10 mm

Sensitivity72.4%

Specificity76.2%

ContextThreshold derived from comparison of diabetic subjects vs controls for early diabetic neuropathy (Umapathi et al., ankle IENFD)

Prior Authorization, Documentation, and Billing Guidance

Denial Risk

Denial Triggers for IENFD Testing

Denial trigger: Missing documentation of painful sensory neuropathy
Denial trigger: History of a predisposing disorder (diabetes, toxic exposure, HIV, celiac disease, inherited neuropathy)
Denial trigger: Clinical or exam evidence of large‑fiber neuropathy (reduced reflexes, impaired proprioception/vibration)
Denial trigger: Abnormal EMG or nerve conduction studies indicating large‑fiber involvement

Note

Risk from Non‑Specialized Processing and Method Limitations

Risk: Commercial processing may not use stereologic quantitative analysis and can miss localized denervation
Risk: Descriptive semi‑quantitative sweat gland innervation methods show poor reliability — avoid for diagnostic quantification
Suggested documentation: biopsy site, fixation method, stains/markers used (eg, PGP 9.5), number of sections quantified, and whether stereologic/morphometric analysis was performed

Documentation Required

Provider Actions / Operational Note

Action: Ensure all medical necessity criteria are documented in the record
Action: Include results of noninvasive testing (NCVS, QST, stimulated skin wrinkling) when available to support indication
Action: Specify biopsy site(s) and laboratory methods (fixation, stains, number of sections, morphometric techniques) in the pathology report
Note: Prior authorization requirements are not specified in this section; check payer prior authorization rules