A Protocol of Manual Tests to Measure Sensation and Pain in Humans

Summary

The goal of this procedure is to demonstrate a battery of quantitative techniques for sensory and pain measurement in humans. The equipment and techniques described are commonly found in pain clinics or are easy to obtain.

Abstract

Numerous qualitative and quantitative techniques can be used to test sensory nerves and pain in both research and clinical settings. The current study demonstrates a quantitative sensory testing protocol using techniques to measure tactile sensation and pain threshold for pressure and heat using portable and easily accessed equipment. These techniques and equipment are ideal for new laboratories and clinics where cost is a concern or a limiting factor. We demonstrate measurement techniques for the following: cutaneous mechanical sensitivity on the arms and legs (von-Frey filaments), radiant and contact heat sensitivity (with both threshold and qualitative assessments using the Visual Analog Scale (VAS)), and mechanical pressure sensitivity (algometer, with both threshold and the VAS). The techniques and equipment described and demonstrated here can be easily purchased, stored, and transported by most clinics and research laboratories around the world. A limitation of this approach is a lack of automation or computer control. Thus, these processes can be more labor intensive in terms of personnel training and data recording than the more sophisticated equipment. We provide a set of reliability data for the demonstrated techniques. From our description, a new laboratory should be able to set up and run these tests and to develop their own internal reliability data.

Introduction

Chronic pain conditions are a worldwide clinical problem. More than 1.5 billion people worldwide suffer from chronic pain, and approximately 5% of the global population suffers from neuropathic pain, with incidence rates increasing with age¹. In America, it is estimated that pain affects more people than diabetes, heart disease, and cancer, combined². While awareness of this problem is increasing, treatments are not always successful, can be expensive, and may have serious side effects, including addiction. Research on treatments is ongoing, but as pain varies greatly between individuals, pain measurement for research or diagnosis can be problema....

Protocol

All tests with human subjects should be approved by the Institutional Review Board at the individual institution. All testing described for the current study was approved by the Duquesne University Institutional Review Board for human subject research. Training for and descriptions of each measure are as follows:

1. Cutaneous Mechanical Sensitivity Assay¹³

NOTE: Enrolled participants are asked to sit in a chair, with support provided for the extremity to be tested. The assay involves determining the sensitivity threshold for innocuous cutaneous stimulation. Stimulation is provided with standard sensory e....

Results

 Here, we describe the implementation of cost-effective qualitative and quantitative assays to measure innocuous sensation and pain in human participants using the VAS (Figure 2). The visual representation is important, because accurate and precise results of these examinations are dependent upon correct and consistent protocol execution by the technician. Additionally, it is valuable to know if multiple technicians performing the technique as described can collect reprod.......

Discussion

We have demonstrated cost-effective and simple qualitative and quantitative sensory tests that can be used to assess mechanical sensation, thermal sensation and pain, and pressure pain in human subjects. The value of these assays is their ease of implementation and low amount of necessary training time. Each experimenter received a minimal amount of training (one trial observation and one trial implementation). Thus, multiple technicians could be trained in one day. The results suggest strong inter-experimenter and withi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Pressure Algometer/Force Dial	Wagner Instruments	FDK 20	The pressure algometer quantifies pressure pain threshold. It has a rubber tip attachment that is applied to the marked skin site by the investigator. The dial records the pressure and is reset after each measurement.
von Frey cutaneous stimulators	Touch Test	NC1275-01 through -08	These von Frey filaments are commonly used to examine sensitivity in research and clinical settings. Our set of 8 filaments covers a range of sensitivities. The individual filaments are 1.65 mN, 2.36 mN, 2.44 mN, 2.83 mN, 3.22 mN, 3.61 mN, 3.84 mN, 4.08 mN.
"Hargreaves" apparatus, testing platform	Custom	n/a	One complete base and four supporting columns are used to form a platform for a sheet of safety glass through which the heat source directs heat to the subjects arm or leg that is resting on the glass. The heat lamp is placed beneath the glass.
0.64 cm Pyrex safety glass	DuPont	n/a	Safety glass is important to avoid injury in the unlikely event of a fracture in the glass surface.
Electronic thermometer/thermocouple 53 IIB	Fluke	3821062	The thermocouple is used for thermal testing. The thermocouple is placed on the glass underneath the subject's arm or leg and measures the temperature at the glass level.
IITC Plantar Analgesia Meter	Life Science Inc. Woodland Hills, CA	390	This is the heat source and timer for Hargreaves testing. The unit's heat source has an “idle state” that allows exact placement of the heat source. The heat source is radiant light and the light beam is focused to the top of the glass to creates a 4 mm x 6 mm intense spot on the arm or leg.
Examiner script	Custom	n/a	A written script for the examiner is used for every testing session. Because pain and sensitivity can be affected by environmental stresses, we attempt to maintain as much consistency as possible between subjects. The examiner reads directly from the script every time a measure is made to ensure verbal consistency.
Markers for testing site	Sharpie	n/a	Washable markers may be preferable for situations where multiple days of testing is not necessary
Constant heat stimulus block	Benchmark Scientific	BR10-00	This block is digitally controlled. The surface of the block is 2 cm x 3 cm.