Single-Center Study Evaluating the Impact of Age on the Diagnostic Performance of the Sural-to-Radial Sensory Amplitude Ratio in Length-Dependent and Non-Length-Dependent Peripheral Polyneuropathies

N/ANot Yet RecruitingNCT07725120

Centre Hospitalier Universitaire de Nice180 enrolled

Overview

This retrospective single-center observational study will evaluate the impact of age on the diagnostic performance of the sural-to-radial sensory nerve amplitude ratio (SRAR) in patients with length-dependent and non-length-dependent peripheral sensory polyneuropathies. Clinical and electrophysiological data collected during routine care between January 2013 and July 2026 will be analyzed. Diagnostic performance will be assessed using receiver operating characteristic (ROC) curve analysis across predefined age groups to determine whether age-adjusted SRAR thresholds improve the differentiation between the two polyneuropathy phenotypes.

Peripheral sensory polyneuropathies are commonly classified as length-dependent (LDN) or non-length-dependent (NLDN) based on their clinical and electrophysiological features. This distinction is clinically important because it guides etiological investigations and therapeutic management. The sural-to-radial sensory nerve amplitude ratio (SRAR) is an electrophysiological marker that has been proposed to improve the diagnosis of sensory polyneuropathies and to help differentiate LDN from NLDN. Although the SRAR has traditionally been considered independent of demographic characteristics, recent evidence suggests that it decreases with aging, raising concerns about the use of a single diagnostic threshold across all age groups. The impact of age on the diagnostic performance of the SRAR, particularly in patients with non-length-dependent polyneuropathies, remains poorly characterized. This retrospective single-center study will analyze clinical and electrophysiological data from patients evaluated at the Peripheral Neuromuscular Rare Disease Reference Center of Nice University Hospital between January 2013 and July 2026. The study aims to determine whether age-adjusted SRAR thresholds improve the diagnostic discrimination between length-dependent and non-length-dependent peripheral polyneuropathies.

Study Type

OBSERVATIONAL

Enrollment

180

Conditions

Polyneuropathies

Interventions

Retrospective Medical Record ReviewOTHER

This observational study involves retrospective collection and analysis of routinely acquired clinical and electrophysiological data from approximately 180 patients with sensory polyneuropathy. Data extracted from medical records include demographic characteristics, clinical diagnosis, and nerve conduction study parameters, including sural and radial sensory nerve action potential amplitudes used to calculate the sural/radial amplitude ratio (SRAR). No additional diagnostic procedures, treatments, or study-specific assessments are performed. All data are obtained from standard clinical care.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 90 Years

Medical Language ↔ Plain English

Inclusion Criteria: * Adults aged 18 years or older. * Diagnosis of peripheral sensory polyneuropathy. * Classification as length-dependent (LDN) or non-length-dependent (NLDN) based on clinical and electrophysiological findings. * Available nerve conduction study including sural and radial sensory nerve amplitudes allowing calculation of the SRAR. * Evaluated at the Peripheral Neuromuscular Rare Disease Reference Center, Nice University Hospital, between January 2013 and July 2026. Exclusion Criteria: * Missing or incomplete clinical or electrophysiological data preventing SRAR calculation. * Unclassifiable neuropathy phenotype. * Technical factors affecting the reliability of nerve conduction studies.

Outcomes

Primary Outcomes

Diagnostic performance of the sural-to-radial sensory nerve amplitude ratio (SRAR)

To evaluate the diagnostic performance of the SRAR for differentiating length-dependent (LDN) from non-length-dependent (NLDN) peripheral sensory polyneuropathies according to age group, using receiver operating characteristic (ROC) curve analysis.

Time frame: Baseline (retrospective analysis of data collected between January 2013 and July 2026

Secondary Outcomes

Age-specific optimal SRAR diagnostic thresholds

To determine the optimal SRAR cutoff values for each predefined age group using the Youden index derived from ROC curve analysis.

Time frame: Baseline (retrospective analysis)

Comparison of SRAR values between LDN and NLDN

To compare SRAR values between patients with length-dependent and non-length-dependent peripheral sensory polyneuropathies and to assess the influence of age on these values.