title: Reliability of pain intensity clamping using response-dependent thermal stimulation in healthy volunteers.
abstract: BACKGROUND
  Pain intensity clamping uses the REsponse-Dependent Stimulation (REDSTIM) methodology to automatically adjust stimulus intensity to maintain a desired pain rating set-point which is continuously monitored from a subject's real-time pain ratings. REDSTIM blinds subjects regarding the pain intensity set-point, supporting its use for assessing intervention efficacy. By maintaining the pain intensity at a constant level, a potential decrease in pain sensitivity can be detected by an increase in thermode temperature (unknown to the subject) and not by pain ratings alone. Further, previously described sensitizing and desensitizing trends within REDSTIM provide a novel insight into human pain mechanisms overcoming limitations of conventional testing methods. The purpose of the present study was to assess the test-retest reliability of pain intensity clamping using REDSTIM during three separate sessions.
  
  
  METHODS
  We used a method for testing changes in pain sensitivity of human subjects (REDSTIM) where the stimulus temperature is modulated to clamp pain intensity near a desired set-point. Temperature serves as the response variable and is used to infer pain sensitivity. Several measures were analyzed for reliability including average temperature and area under the curve (AUC). Intraclass correlation coefficients were calculated for each measure at pain rating set-points of 20/100 and 35/100.
  
  
  RESULTS
  Sixteen healthy individuals (mean age = 21.6 ± 3.9) participated in three experiments two days apart at both pain rating set-points. Most reliability coefficients were in the moderate to substantial range (r's = 0.79 to 0.94) except for the negative AUC (r = 0.52), but only at the 20/100 pain rating set-point.
  
  
  CONCLUSIONS
  The present study supports the test-retest reliability of pain intensity clamping using the REDSTIM methodology while providing a novel tool to examine human pain modulatory mechanisms and overcoming common shortcomings of conventional quantitative sensory testing methods.
authors.affiliation: Institute on Aging, University of Florida, Gainesville, FL, USA. cryeni@ufl.edu.|Cognitive Aging & Memory, University of Florida, Gainesville, FL, USA. cryeni@ufl.edu.|Pain Research and Intervention Center of Excellence, Gainesville, USA. cryeni@ufl.edu.|Department of Aging & Geriatric Research, College of Medicine, University of Florida, Gainesville, FL, USA. cryeni@ufl.edu.|Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL, USA. cryeni@ufl.edu.|Department of Community Dentistry & Behavioral Sciences, College of Dentistry, University of Florida, Gainesville, FL, USA. cryeni@ufl.edu.
authors.forename: Yenisel
authors.initials: Y
authors.lastname: Cruz-Almeida
authors.affiliation: Department of Kinesiology, IUPUI, Indianapolis, IN, USA. kmnaugle@iupui.edu.
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Naugle
authors.affiliation: Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL, USA. vierck@ufl.edu.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Vierck
authors.affiliation: Institute on Aging, University of Florida, Gainesville, FL, USA. rfillingim@dental.ufl.edu.|Pain Research and Intervention Center of Excellence, Gainesville, USA. rfillingim@dental.ufl.edu.|Department of Community Dentistry & Behavioral Sciences, College of Dentistry, University of Florida, Gainesville, FL, USA. rfillingim@dental.ufl.edu.
authors.forename: Roger B
authors.initials: RB
authors.lastname: Fillingim
authors.affiliation: Pain Research and Intervention Center of Excellence, Gainesville, USA. jriley@dental.ufl.edu.|Department of Community Dentistry & Behavioral Sciences, College of Dentistry, University of Florida, Gainesville, FL, USA. jriley@dental.ufl.edu.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Riley
mesh_terms: D000328:Adult; D019540:Area Under Curve; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010147:Pain Measurement / Q000379:methods*; D017288:Pain Threshold; D010812:Physical Stimulation / Q000379:methods*; D015203:Reproducibility of Results; D055815:Young Adult