A Comprehensive Review of the Clinical Utility and Reliability of a Quantitative Electrical Stimulation Device for Objective Pain Assessment

Abstract

Objective

Objective pain measurement remains challenging due to pain’s subjective nature. This review evaluates the clinical utility, measurement protocols, reliability, and limitations of a quantitative electrical stimulation device used for objective pain perception threshold assessment.

Methods

A systematic literature search was conducted in November 2025 using Web of Science and PubMed databases without date restrictions. Studies involving human subjects that employed the device for quantitative pain perception threshold measurement were included. Data on study design, patient populations, measurement protocols, clinical applications, reliability, and validity were extracted and synthesized.

Results

Eleven studies met inclusion criteria, encompassing healthy volunteers and patients with neuropathic pain, chemotherapy-induced peripheral neuropathy, chronic pain, and genetic pain sensitivity disorders. The device quantified current perception threshold (CPT) and pain equivalent current (PEC) via controlled electrical stimulation, with electrode placement typically on the forearm, upper arm, fingertips, or ulnar flexion. Measurements demonstrated reproducibility and positive correlations with subjective pain scales such as the Visual Analog Scale (VAS). Variability in protocols, sensitivity to patient movement, and limited assessment of slow C-fiber mediated pain were commonly reported challenges.

Conclusion

The electrical pain assessment device is a promising objective tool for pain and sensory function assessment that complements subjective measures. Future research should focus on large-scale validation, standardization of protocols, and integration with other physiological markers to enhance clinical applicability and precision in pain management.

Plain Language Summary

This review focuses on a device called Pain Vision^®, which measures how sensitive a person is to electrical stimulation, helping to assess pain and sensory function more objectively than traditional methods. Pain is difficult to measure because it is subjective and can vary widely among individuals. Accurate pain assessment is important for diagnosing conditions, monitoring treatments, and making decisions about medication.

The researcher examined 11 recent clinical studies that used the electrical pain assessment device in different groups, including healthy people and patients with conditions like neuropathic pain, chemotherapy-induced nerve damage, and postoperative pain. The device was found to provide reliable and reproducible measurements, offering clear advantages over subjective pain scales by giving precise, numerical data on pain levels.

However, challenges remain, such as small study sizes, differences in how the device is used across studies, and its sensitivity to patient movement. The device cannot fully measure all types of pain, especially pain carried by certain nerve fibers. Still, combining this objective tool with traditional pain assessments can improve overall accuracy.

Using the electrical pain assessment device can help doctors better understand and manage pain, leading to safer use of pain medications. This is important because some pain treatments, like opioids and anti-inflammatory drugs, can cause serious side effects if not used carefully. Objective pain measurement supports safer prescribing and helps avoid under- or over-treatment.

In summary, the electrical pain assessment device represents a promising step toward more precise and objective pain assessment. Its use could improve patient care, support personalized treatment, and reduce risks associated with pain medication. Further research and standardization will help maximize its clinical benefits.

Introduction

Pain is a complex, multidimensional experience that serves as a vital signal for tissue damage, yet its management remains one of the most significant challenges in modern medicine. Traditionally, the gold standard for pain assessment has relied almost exclusively on patient-reported outcomes, such as the Visual Analog Scale (VAS), Numerical Rating Scale (NRS), and various qualitative questionnaires.¹ While these subjective tools are indispensable for clinical practice, it is well-established that they are inherently limited by high inter-individual variability, cognitive biases, and psychological factors such as mood or social isolation. For instance, the VAS is known to have a margin of error of approximately ±20 mm, which can obscure subtle but clinically significant changes in pain intensity or treatment efficacy.² Alternative objective techniques, such as quantitative sensory testing (QST) and neuroimaging, have been developed to complement subjective assessments. QST is an objective method used to evaluate sensory nerve function by measuring responses to controlled sensory stimuli. It assesses various sensory modalities such as thermal, mechanical, and vibration thresholds to detect sensory abnormalities or neuropathic pain conditions. QST involves applying standardized stimuli of controlled intensity and recording the subject’s perception thresholds or pain thresholds. This approach helps quantify sensory disturbances like hypoesthesia, hyperalgesia, or allodynia.

However, it typically requires specialized equipment, trained personnel, and can be time-consuming, which limits its routine use in clinical practice. Despite these limitations, QST remains valuable for diagnosing neurological disorders, characterizing pain phenotypes, and monitoring treatment efficacy.

To bridge these diagnostic gaps, electrical pain assessment systems have emerged as non-invasive, neuro-electrophysiological tools for pain quantification.³ These devices calculate a quantitative “Pain Degree” (or “Pain Ratio”) by comparing the Current Perception Threshold (CPT)—the minimum stimulus detectable by the subject—with the Pain Equivalent Current (PEC), which is the electrical stimulation intensity that matches the patient’s existing perceived pain.⁴ By normalizing the pain stimulus against an individual’s own baseline sensory threshold, this methodology effectively mitigates physiological differences between patients, enhancing the objectivity and comparability of the data.² The clinical validity of this approach is supported by its status as a reimbursable procedure under the Japanese national health insurance system and its compliance with stringent safety standards, such as those set by the US Food and Drug Administration (FDA).

However, several aspects of this technology remain poorly understood or limited, justifying the requirement for a critical review. First, these devices primarily stimulate Aβ and Aδ nerve fibers, which transmit sharp, momentary pain, but they are generally incapable of stimulating C-fibers, which are responsible for the “slow” burning pain characteristic of many chronic or inflammatory conditions.⁵ Second, while the device is excellent for intra-individual monitoring, it remains difficult to compare absolute numerical values between different participants due to significant baseline variations in pain perception.³ Third, some research has indicated that electrical assessment may exhibit higher intra-individual variation than VAS in certain neuropathic contexts, the causes of which require further investigation.⁶ Finally, there is a lack of large-scale, prospective trials to establish universal diagnostic “cutoff” values for many clinical conditions.⁵

This review critically summarizes and analyzes recent clinical studies that employed the electrical pain assessment device, focusing on its measurement protocols, clinical applications, reliability, and limitations. Through this focused examination, this review elucidates the current role and future prospects in enhancing objective pain assessment and management strategies within clinical settings.

Methods

A literature search was conducted on November 2025 using Web of Science and PubMed databases without date restrictions, using the keyword “The electrical pain assessment device”. The inclusion criteria were human studies focusing on the clinical applications of the electrical pain assessment device, excluding review articles. Screening involved title and abstract reviews followed by full-text evaluations. EndNote software was used for literature management and removal of duplicates.

Titles and abstracts were screened to exclude irrelevant articles, animal studies, and reviews. Full-text screening was then performed to select studies that met the inclusion criteria: original research articles involving human subjects, use of the electrical pain assessment device for quantitative perception threshold assessment, and availability of detailed methodological and outcome data. Data extraction included study design, patient population characteristics, device measurement protocols (electrode placement, stimulation parameters), clinical applications, reliability and validity assessments, and reported limitations.

Objective quantitative evaluation of sensory disturbances using PainVisionⓇ PS-2100 was performed following attached documents. Electrodes were placed on hairless, flat areas of the body, specifically on the forearms and palms, identified as optimal measurement sites. Electrode plates were affixed to the proximal one-third of the flexor side of the forearm, positioned slightly closer to the ulna, and to the center of the palm. Electrical stimulation was gradually increased within a range of 0 to 150 μA (50 Hz frequency; pulse width of 0.3 ms). The minimal current intensity perceived as electrical stimulation was defined as the current perception threshold (CPT) and recorded. Each measurement was repeated three times, and the average bilateral CPT values for the forearm and palm were calculated to ensure reliability.⁷

Results

Literature Selection Process

A systematic literature search was conducted in November 2025 using Web of Science and PubMed databases with the keyword “Pain Vision”. No date restrictions were applied. The initial search yielded 150 articles from Web of Science and 67 from PubMed, totaling 217 articles.

Duplicate records were removed using EndNote software. A first screening, based on titles and abstracts, excluded irrelevant articles, animal studies, and reviews, resulting in 42 articles from Web of Science and 10 from PubMed, totaling 52 articles for full-text screening.

The second screening involved full-text evaluation focusing on clinical or experimental studies employing the quantitative electrical stimulation device for perception threshold assessment. Studies lacking methodological details or relevant data were excluded. Ultimately, 11 articles met all inclusion criteria and were included in this review. The key findings are summarized in Table 1.

Table 1.

Summary of Studies Using the Quantitative Electrical Stimulation Device for Perception Threshold Assessment

Author (Year)	Country	Journal	Target Disease/Subject Attributes	Study Design	Method	Stimulation & Assessment Procedures	Reliability & Validity (Quantitative Indicators)
Fukada et al8 (2011)	Japan	Eur J Anaesthesiol	Analgesic effect of transdermal nicotine patches; healthy non-smoking volunteers (n=40)	Randomized double-blind crossover trial	Pain Vision, NRS.	Measured CPT and PT on the right hand under pressure pain.	No significant differences were observed between nicotine and placebo groups in CPT, PT, pain degree, or NRS.
Hiraki et al9 (2014)	Japan	Surgical Endoscopy	Postoperative pain in colon cancer patients (n=22)	Case-control study	Pain Vision, VAS.	Pain evaluated at rest and during mobilization on POD 1–7.	PV intensity at rest showed a significant reduction in SLC vs MLC over the period (p = 0.003). VAS during mobilization was also significant (p = 0.009).
Yoshida et al2 (2015)	Japan	SpringerPlus	Sensory perception evaluation of peripheral neuropathy (PN) in colorectal cancer patients (n=58)	Observational study	Pain Vision, VAS.	VAS and PV assessments compared across 173 measurements during chemotherapy.	Partial correlation coefficient (adjusted for sex/subject) was 0.274 (p = 0.0003), indicating a weak but significant correlation between PV and VAS.
Kiyomi et al6 (2016)	Japan	BMC Research Notes	Oxaliplatin-induced neuropathy in colorectal cancer patients (n=43)	Observational study	Pain Vision, VAS.	Comparison of intra-individual VAS and PV.	Difference in intra-individual coefficients of variation (CV) was 0.96 (95% CI: −1.59, −0.33), indicating higher intra-individual variation in PV compared to VAS.
Sato et al5 (2017)	Japan	BMC Research Notes	Objective evaluation of chemotherapy-induced peripheral neuropathy (CIPN) in gynecological cancer patients (n=41)	Pilot study	Pain Vision, CTC-AE, PNQ.	Measured before and during 6 cycles of taxane/platinum therapy.	Pain degree significantly decreased at Grade 1 CIPN (69.8 ± 46.8) and Grade 2 (32.8 ± 32.6) vs. baseline (126.0 ±114.5) (p = 0.001, 0.004)
Horikiri et al4 (2018)	Japan	J Plast Surg Hand Surg	Pain assessment in capillary malformation treatment (n=20)	Clinical crossover trial	Pain Vision, VAS.	595-nm pulsed dye laser (V-Beam) irradiation (10 J/cm2) applied 1h after anesthetic application.	PV intensity was significantly lower for Emla (1.32) than Penles (3.39) (p = 0.0426). VAS showed no significant difference (p = 0.5422).
Sawai et al10 (2019)	Japan	J Nutr Sci Vitaminol	Effect of mental stress on pain perception in healthy adult males (n=30)	Experimental/Interventional study	Pain Vision, Taste Disk®, ECG.	10-minute mental arithmetic task; measured skin current thresholds on the inner forearm.	Stress significantly increased thresholds for forearm skin pain and pungency (p < 0.05), while decreasing cognitive thresholds for 3 basic tastes (p < 0.05).
Antioch et al11 (2020)	Romania/Japan	Journal of Pain Research	Effect of music on pain threshold in healthy volunteers (n=30)	Experimental study	Pain Vision, fMRI (1.5T).	Forearm pain thresholds compared with/without music. 80-μA current applied to ankle for fMRI.	Median pain threshold with music (38.9μA) was significantly higher than without (29.0μA) (p < 0.0001). ACC activity was attenuated in 5/8 subjects.
Wang et al12 (2020)	China	Pain Research and Management	Neuroelectrophysiological evaluation of chronic pain patients (n=71)	Correlational study pre- and post-treatment	Pain Vision, VAS.	Compare before/after treatment.	Pearson correlation coefficient was 0.730 before treatment and 0.449 after (p < 0.001). Before treatment regression: Pain Ratio = 0.782, VAS - 2.252
Rikihisa et al13 (2023)	Japan	PLoS ONE	Pain assessment during new surgical tape removal; healthy adult males (n=5)	Experimental/Interventional Study	Pain Vision, Video analysis.	Tapes removed 8h after application (120° angle). Compared mesh tape (leave vs. remove mesh) and control.	Friedman test: Significant difference in pain among methods (p < 0.001).
Li et al14 (2024)	China	Am J Med Genet Pt A	Pain perception in P2RX2 gene mutation carriers (n=4; 2 affected, 2 unaffected)	Case report/Observational study	Pain Vision, VAS.	Electrical stimulation (50Hz) to inner forearm to find CPT and PT.	PTs of mutation carriers (27.1, 27.2 μA) were significantly lower than unaffected members (44.8, 93.0 μA). PD showed a corresponding decrease in carriers.

Notes: This table presents an overview of 11 selected studies that employed a quantitative electrical stimulation device for perception threshold assessment across various clinical and experimental contexts. It summarizes key information including authorship, country, publication details, target diseases and subject attributes, study designs, measurement procedures and reliability/validity. The compilation highlights the device’s application spectrum, methodological diversity, and current evidence regarding its clinical utility and constraints. CTC-AE: Common Terminology Criteria for Adverse Events; A standardized classification system utilized by medical professionals to grade the severity of adverse effects, such as chemotherapy-induced peripheral neuropathy, ranging from grade 1 (mild/asymptomatic) to higher grades based on clinical impact. PNQ: Patient Neurotoxicity Questionnaire; A patient-reported outcome measure designed to subjectively evaluate the severity of peripheral neuropathy through a five-grade scale (Scale A to E), focusing on how symptoms like numbness or tingling interfere with a patient’s activities of daily living (ADL). Taste Disk^®: A clinical assessment tool that employs the filter-paper disc method to determine the detection and recognition thresholds for basic tastes (sweet, salty, sour, and bitter) by applying reagent solutions of varying concentrations to the tongue.

Abbreviations: CPT/PT, Current Perception Threshold/Perception Threshold; NRS, Numerical Rating Scale; PCC/PEC, Pain Compatible Current/Pain Equivalent Current; VAS, Visual Analog Scale; PV, Pain Vision measurement value; POD, Postoperative days POD; SLC/MLC, Types of surgical procedures; CIPN, Chemotherapy-Induced Peripheral Neuropathy; PN, Peripheral Neuropathy.

Country and Study Population

Eight studies originated from Japan,^{2,4–6,8–10,13} two from China^12,14 and one from Romania/Japan collaboration.¹¹ The study population included healthy volunteers, patients with neuropathic pain related to cancer or chemotherapy-induced peripheral neuropathy (CIPN), chronic pain patients, and individuals with capillary malformations or genetic pain sensitivity disorders. Sample sizes ranged from small pilot groups to larger cohorts.

Study Designs

The designs comprised experimental/interventional studies, randomized double-blind crossover trials, observational and pilot studies, clinical crossover trials, and case-control studies.

Measurement Purpose and Protocols

The device was used to objectively quantify pain stimuli, evaluate analgesic effects, assess pain hypersensitivity in genetic mutation carriers, compare variability between subjective and objective measures, and monitor treatment effects. Measurement protocols typically involved electrodes placed on the forearm, upper arm, fingertips, or ulnar flexion, with electrical stimulation intensity gradually increased to record current perception threshold (CPT) and pain equivalent current (PEC/PCC). Most studies conducted multiple measurements per session, averaging the results to enhance reliability. Specific procedural details varied, such as stimulation parameters and the number of trials, but all adhered to the principle of controlled, incremental electrical stimulation.

Reliability and Validity

Device measurements showed positive correlations with subjective pain scales such as the Visual Analog Scale (VAS) and Numerical Rating Scale (NRS), although the strength of correlations varied across studies. Reproducibility and intra-subject consistency were demonstrated in multiple studies, including randomized crossover trials and observational designs. Quantitative reliability indicators such as intra-class correlation coefficients (ICC) and test-retest correlation coefficients were reported where available, confirming good measurement stability. Psychological and environmental factors were found to have minimal but notable influences on measurements, emphasizing the importance of standardized testing conditions.

Challenges and Limitations

Common limitations included small sample sizes, variability in measurement protocols and electrode placement, sensitivity to patient movement, difficulty detecting slow C-fiber mediated pain, and the need for operator training. The device’s applicability was limited to certain anatomical sites. Combining device data with subjective assessments is recommended for comprehensive pain evaluation.

Discussion

The results of this review, based on 11 selected studies employing a quantitative electrical stimulation device for perception threshold assessment (hereafter “the device”), demonstrate its promising role as an objective and reproducible tool for pain and sensory function evaluation across diverse clinical and experimental contexts. The device’s applications span neuropathic pain,^2,3 postoperative pain,⁹ chemotherapy-induced peripheral neuropathy (CIPN),^5,6 and the modulation of pain perception by psychological¹⁰ and environmental factors.¹¹ Quantitative indices, such as the current perception threshold (CPT) and pain equivalent current (PEC) have shown advantages over traditional subjective measures like the Visual Analog Scale (VAS), particularly in enhancing objectivity and enabling longitudinal monitoring of treatment effects.

The observed correlations between device-derived metrics and subjective pain scales, although generally positive, are sometimes modest, suggesting these tools capture complementary but distinct aspects of pain experience.^8,13 This supports the combined use of objective and subjective assessments to achieve comprehensive pain evaluation.

Importantly, the objective assessment of pain is critical in clinical practice and medico-legal contexts. Pain’s inherently subjective nature complicates accurate evaluation, which can lead to challenges such as malingering or exaggeration, particularly in disputes like traffic accidents. Objective tools like this device can provide reproducible data to aid fair conflict resolution and prevent unnecessary litigation.¹⁵

Moreover, precise pain quantification is vital for guiding pharmacotherapy, as pain-related medications carry significant risks if prescribed based solely on subjective reports. The opioid crisis exemplifies the dangers of overprescription, with addiction, overdose, and mortality as grave consequences. Similarly, nonsteroidal anti-inflammatory drugs (NSAIDs) pose risks of renal impairment, gastrointestinal ulcers, and bleeding,¹⁶ while acetaminophen overdose can cause hepatotoxicity and acute liver failure. These adverse events highlight the necessity of accurate, quantitative pain assessment to inform appropriate prescribing and minimize harm.

The device’s integration into clinical workflows can improve analgesic management by enabling tailored, safer treatment strategies, reducing the likelihood of overtreatment or undertreatment. Objective pain measurements enhance patient-clinician communication and trust and support equitable medico-legal processes.¹⁷

Future research should prioritize large-scale, multicenter validation studies to establish normative data and clinical thresholds. Development of consensus guidelines for measurement protocols and integration with complementary physiological markers—such as heart rate variability and neuroimaging—could enhance diagnostic precision and mechanistic understanding.¹⁸ Technological advancements aimed at automating measurements, minimizing operator dependency, and improving patient comfort are critical.¹⁹ Addressing these challenges will be essential for the device to fulfill its potential as a precision tool in pain medicine, facilitating personalized treatment and improving patient outcomes.

This study has several limitations that should be acknowledged. First, the small sample sizes in many of the included studies limit the statistical power and generalizability of the findings, making it difficult to draw definitive conclusions about the device’s clinical utility across diverse populations.^4–6,13 Second, variability in measurement protocols, including differences in electrode placement and stimulation parameters, hinders cross-study comparisons and underscores the need for standardized procedures to ensure consistent and reproducible results. Third, the device’s sensitivity to patient movement and its limited ability to assess slow C-fiber mediated pain restrict the scope of pain modalities that can be effectively evaluated, potentially limiting its applicability in certain clinical scenarios. Addressing these limitations in future research will be essential to fully validate and optimize the device’s role in pain assessment.

Conclusion

The quantitative electrical stimulation device for perception threshold assessment provides a significant advancement in the objective evaluation of pain and sensory function across diverse clinical settings.^{2,4–6,8–13} It offers improved accuracy and reproducibility compared to traditional subjective scales, enabling more precise diagnosis and monitoring of neuropathic pain,^2,3 postoperative pain,⁹ chemotherapy-induced peripheral neuropathy (CIPN),^5,6 and the modulation of pain perception by psychological¹⁰ and environmental factors.¹¹ The device’s ability to deliver quantitative indices such as current perception thresholds and pain equivalent currents facilitates longitudinal assessment and personalized pain management strategies.

However, challenges remain, including small sample sizes in many studies,^4–6,13 sensitivity to patient movement, and limited detection of certain pain modalities, such as slow C-fiber mediated pain. The device’s measurements complement rather than replace subjective assessments, supporting a multimodal approach to pain evaluation.

Future research should focus on large-scale, multicenter validation studies, development of consensus guidelines, and integration with other physiological markers to improve diagnostic precision and mechanistic understanding. Technological innovations that automate measurements and reduce operator dependency will further optimize clinical utility. Addressing these issues is essential for the device to fulfill its potential as a precision tool in pain medicine, ultimately improving patient outcomes through safer and more effective pain management.

Funding Statement

The article processing charge was supported by Kobayashi Funding and research funds from Tsumura & Co.

Disclosure

The author reports no conflicts of interest in this work.