title: Is the conditioned pain modulation paradigm reliable? A test-retest assessment using the nociceptive withdrawal reflex.
abstract: The aim of this study was to determine the reliability of the conditioned pain modulation (CPM) paradigm assessed by an objective electrophysiological method, the nociceptive withdrawal reflex (NWR), and psychophysical measures, using hypothetical sample sizes for future studies as analytical goals. Thirty-four healthy volunteers participated in two identical experimental sessions, separated by 1 to 3 weeks. In each session, the cold pressor test (CPT) was used to induce CPM, and the NWR thresholds, electrical pain detection thresholds and pain intensity ratings after suprathreshold electrical stimulation were assessed before and during CPT. CPM was consistently detected by all methods, and the electrophysiological measures did not introduce additional variation to the assessment. In particular, 99% of the trials resulted in higher NWR thresholds during CPT, with an average increase of 3.4 mA (p<0.001). Similarly, 96% of the trials resulted in higher electrical pain detection thresholds during CPT, with an average increase of 2.2 mA (p<0.001). Pain intensity ratings after suprathreshold electrical stimulation were reduced during CPT in 84% of the trials, displaying an average decrease of 1.5 points in a numeric rating scale (p<0.001). Under these experimental conditions, CPM reliability was acceptable for all assessment methods in terms of sample sizes for potential experiments. The presented results are encouraging with regards to the use of the CPM as an assessment tool in experimental and clinical pain. Trial registration: Clinical Trials.gov NCT01636440.
authors.affiliation: Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: José A
authors.initials: JA
authors.lastname: Biurrun Manresa
authors.affiliation: University Department of Anaesthesiology and Pain Therapy, Inselspital, Bern, Switzerland.
authors.forename: Raphael
authors.initials: R
authors.lastname: Fritsche
authors.affiliation: Department of Anaesthesiology and Pain Medicine, University of Washington, Seattle, United States of America.
authors.forename: Pascal H
authors.initials: PH
authors.lastname: Vuilleumier
authors.affiliation: University Department of Anaesthesiology and Pain Therapy, Inselspital, Bern, Switzerland.
authors.forename: Carmen
authors.initials: C
authors.lastname: Oehler
authors.affiliation: Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Carsten D
authors.initials: CD
authors.lastname: Mørch
authors.affiliation: Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
authors.affiliation: Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Ole K
authors.initials: OK
authors.lastname: Andersen
authors.affiliation: Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark; Department of Anaesthesiology and Pain Medicine, University of Washington, Seattle, United States of America.
authors.forename: Michele
authors.initials: M
authors.lastname: Curatolo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003080:Cold Temperature; D003213:Conditioning, Psychological / Q000502:physiology*; D004558:Electric Stimulation; D055724:Electrophysiological Phenomena; D006801:Humans; D008297:Male; D008875:Middle Aged; D059225:Nociception; D010146:Pain / Q000503:physiopathology* / Q000523:psychology*; D011601:Psychophysics; D012018:Reflex / Q000502:physiology*; D015203:Reproducibility of Results; D055815:Young Adult