Developing an Objective Measure of Experienced Pain

Pain is a public health challenge around the world. However, there is no single standardized measure of pain, to the point that the estimated prevalence of chronic pain in adults ranges between 2% and 64% depending on the methods and definitions used. Existing measures of pain are known to present several problems and results can be hardly compared between people.

The investigators propose and empirically validate a new, simple method to measure experienced pain in clinical trials. The method provides an objective, cardinal measurement of experienced pain which is comparable between people and the investigators test whether it is better able to measure experienced pain than existing procedures. The investigators test the new method in healthy participants using standard protocols (electrical and heat stimuli). The investigators also aim to validate the measure using a causal manipulation which relies on the administration of a topical analgesic product compared to a placebo.

Study Overview

• Status: Completed
• Conditions: Pain, Acute
• Intervention / Treatment: Behavioral: Developing an objective measure of experienced pain

Detailed Description

The aim of this study is to establish and validate the proposed method of measuring pain using different pain stimuli. The investigators correlate these measurements with physiological data such as skin-conductance, heart-rate variability, pupil dilation, and with established measures of pain such as Numeric rating scale (NRS), Visual analog scale (VAS), general Labeled Magnitude Scale (gLMS). In addition, the investigators study the test-retest reliability of our measure of pain and its ability to capture a reduction in experienced pain due to a topical analgesic product compared to a placebo treatment.

• Study Type: Interventional
• Enrollment (Actual): 330
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Switzerland
  • CH
    • Zürich, CH, Switzerland, 8091
      • SNS Laboratory

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 60 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• age 18-60 years.
• ability and willingness to participate in the study
• declaration of consent
• good English language skills (to ensure understanding of all instructions and the declaration of consent).

Exclusion Criteria:

• inability to give the declaration of consent (e.g. due to linguistic difficulties understanding the study information)
• any neurological disorders
• reduced general health / chronic diseases (e.g. autoimmune disease, severe cardiovascular diseases, insulin-dependent diabetes, severe depression); chronic pain disorders
• pregnancy
• in the week before the experimental session self-reported intake of drugs which could influence pain perception (e.g. cannabis and ADHD medications).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

7

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Study 1 Low-Intensity Group; Control group which receives less intense electrical stimuli than the other.	Behavioral: Developing an objective measure of experienced pain; At the beginning of each study, participants are randomly allocated into one of two groups. Within each group all participants are exposed to the same painful stimulus. One group experiences a painful stimulus of higher intensity compared to that of the other group. The painful stimuli are physically identical for every subject within the same group and within the standard of previous pain research. Participants are then asked to evaluate the painful stimulus they just received according to a self-reported scale (NRS, VAS, gLMS, NRS-MB). Participants are also asked to decide multiple times whether they prefer a larger amount of money and experience the same or more painful stimulus they received before or a smaller amount of money and no (or a less) painful stimulus. The smaller amount of money is progressively increased across choices until it matches the larger amount, similar to multiple price-list methods (MPL) which are standard in economics.
Experimental: Study 1 High-Intensity Group; Group which receives more intense electrical stimuli than the other.	Behavioral: Developing an objective measure of experienced pain; At the beginning of each study, participants are randomly allocated into one of two groups. Within each group all participants are exposed to the same painful stimulus. One group experiences a painful stimulus of higher intensity compared to that of the other group. The painful stimuli are physically identical for every subject within the same group and within the standard of previous pain research. Participants are then asked to evaluate the painful stimulus they just received according to a self-reported scale (NRS, VAS, gLMS, NRS-MB). Participants are also asked to decide multiple times whether they prefer a larger amount of money and experience the same or more painful stimulus they received before or a smaller amount of money and no (or a less) painful stimulus. The smaller amount of money is progressively increased across choices until it matches the larger amount, similar to multiple price-list methods (MPL) which are standard in economics.
Active Comparator: Study 2 Low-Intensity Group; Control group which receives less intense heat stimuli than the other.	Behavioral: Developing an objective measure of experienced pain; At the beginning of each study, participants are randomly allocated into one of two groups. Within each group all participants are exposed to the same painful stimulus. One group experiences a painful stimulus of higher intensity compared to that of the other group. The painful stimuli are physically identical for every subject within the same group and within the standard of previous pain research. Participants are then asked to evaluate the painful stimulus they just received according to a self-reported scale (NRS, VAS, gLMS, NRS-MB). Participants are also asked to decide multiple times whether they prefer a larger amount of money and experience the same or more painful stimulus they received before or a smaller amount of money and no (or a less) painful stimulus. The smaller amount of money is progressively increased across choices until it matches the larger amount, similar to multiple price-list methods (MPL) which are standard in economics.
Experimental: Study 2 High-Intensity Group; Group which receives more intense heat stimuli than the other.	Behavioral: Developing an objective measure of experienced pain; At the beginning of each study, participants are randomly allocated into one of two groups. Within each group all participants are exposed to the same painful stimulus. One group experiences a painful stimulus of higher intensity compared to that of the other group. The painful stimuli are physically identical for every subject within the same group and within the standard of previous pain research. Participants are then asked to evaluate the painful stimulus they just received according to a self-reported scale (NRS, VAS, gLMS, NRS-MB). Participants are also asked to decide multiple times whether they prefer a larger amount of money and experience the same or more painful stimulus they received before or a smaller amount of money and no (or a less) painful stimulus. The smaller amount of money is progressively increased across choices until it matches the larger amount, similar to multiple price-list methods (MPL) which are standard in economics.
Placebo Comparator: Study 3 Placebo group; A group that receives a placebo cream.	Behavioral: Developing an objective measure of experienced pain; At the beginning of each study, participants are randomly allocated into one of two groups. Within each group all participants are exposed to the same painful stimulus. One group experiences a painful stimulus of higher intensity compared to that of the other group. The painful stimuli are physically identical for every subject within the same group and within the standard of previous pain research. Participants are then asked to evaluate the painful stimulus they just received according to a self-reported scale (NRS, VAS, gLMS, NRS-MB). Participants are also asked to decide multiple times whether they prefer a larger amount of money and experience the same or more painful stimulus they received before or a smaller amount of money and no (or a less) painful stimulus. The smaller amount of money is progressively increased across choices until it matches the larger amount, similar to multiple price-list methods (MPL) which are standard in economics.
Experimental: Study 3 Painkiller group; A group that receives a topical analgesic such as EMLA cream.	Behavioral: Developing an objective measure of experienced pain; At the beginning of each study, participants are randomly allocated into one of two groups. Within each group all participants are exposed to the same painful stimulus. One group experiences a painful stimulus of higher intensity compared to that of the other group. The painful stimuli are physically identical for every subject within the same group and within the standard of previous pain research. Participants are then asked to evaluate the painful stimulus they just received according to a self-reported scale (NRS, VAS, gLMS, NRS-MB). Participants are also asked to decide multiple times whether they prefer a larger amount of money and experience the same or more painful stimulus they received before or a smaller amount of money and no (or a less) painful stimulus. The smaller amount of money is progressively increased across choices until it matches the larger amount, similar to multiple price-list methods (MPL) which are standard in economics.
No Intervention: Study 4 test-retest reliability group; Participants who participated in either Study 1 or 2 are recruited. They will experience both electrical and heat stimuli.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Choices between monetary amounts and painful stimuli	Participants' choices between monetary amounts and painful stimuli	baseline
self-reported pain ratings according to Numerical Rating Scale (NRS)	self-reported pain ratings according to Numerical Rating Scale	baseline
self-reported pain ratings according to Visual Analogue Scale (VAS)	self-reported pain ratings according to Visual Analogue Scale	baseline
self-reported pain ratings according to general Labeled Magnitude Scale (gLMS)	self-reported pain ratings according to general Labeled Magnitude Scale	baseline
response times	Response times relative to participants' choices between monetary amounts and painful stimuli	baseline

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
heart rate variability	variation in heat-beat rate in reaction to the painful stimuli.	baseline
skin conductance	variation in skin conductance in reaction to the painful stimuli.	baseline
pupil dilation	variation in pupil dilation in reaction to the painful stimuli.	baseline

Collaborators and Investigators

• Sponsor: University of Zurich
• Collaborators: Balgrist University Hospital

Study record dates

Study Major Dates

• Study Start (Actual): June 6, 2022
• Primary Completion (Actual): September 26, 2022
• Study Completion (Actual): September 26, 2022

Study Registration Dates

• First Submitted: May 30, 2022
• First Submitted That Met QC Criteria: June 8, 2022
• First Posted (Actual): June 13, 2022

Study Record Updates

• Last Update Posted (Actual): October 12, 2022
• Last Update Submitted That Met QC Criteria: October 10, 2022
• Last Verified: October 1, 2022

More Information

Terms related to this study

• Keywords: Pain; Measurement of Pain
• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Acute Pain
• Other Study ID Numbers: 2022-00236

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No