title: The UVB cutaneous inflammatory pain model: a reproducibility study in healthy volunteers.
abstract: BACKGROUND
  The human ultraviolet-B (UVB) experimental pain model induces cutaneous neurogenic inflammation, involves hyperalgesia, and is widely used as a pharmacological screening pain model.
  
  
  OBJECTIVE
  To estimate the test-retest reliability of the UVB pain model by application of a comprehensive set of vasomotor and quantitative sensory assessment methods and to estimate sample sizes required for parallel or crossover pharmacological screening studies when this model is considered to be applied.
  
  
  METHODS
  The upper arms of 15 healthy male volunteers were UVB irradiated with three times the minimal erythema dose. Neurogenic inflammation was assessed by measuring erythema index, superficial blood flow and skin temperature at baseline, 1 day, 2 days and 3 days post irradiation. Sensory changes were assessed by brush stroke, von Frey hairs, pressure algometry, heat-evoked pain, stimulus response function to weight calibrated pin-prick stimulation, and the area of secondary hyperalgesia. The experiment was repeated with a two-week interval. Systematic bias, Coefficient of variation (CV), and intra-class correlation (ICC) were calculated within and between UVB irradiations. The sample sizes for parallel and crossover studies were calculated.
  
  
  RESULTS
  Neurogenic inflammation (erythema index) and primary hyperalgesia (pin-prick stimulation) remained significant for 3 days, and were highly reproducible within and between the UVB irradiations resulting of low sample sizes (4-26) in both parallel and crossover studies.
  
  
  CONCLUSIONS
  Based on sample size calculations, it is recommended to use the erythema index to assess neurogenic inflammation, and pin-prick stimulation for primary hyperalgesia for both parallel and crossover pharmacological screening studies.
authors.affiliation: Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University Denmark.
authors.forename: Carsten Dahl
authors.initials: CD
authors.lastname: Mørch
authors.affiliation: Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University Denmark.
authors.forename: Parisa
authors.initials: P
authors.lastname: Gazerani
authors.affiliation: Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University Denmark.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Nielsen
authors.affiliation: Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
keywords: Ultraviolet-B; primary hyperalgesia; quantitative sensory test; reproducibility; sample size; secondary hyperalgesia