Study To Assess The Reproducibility And Sensitivity Of Quantitative Sensory Testing In Patients With Neuropathic Pain

• Mean Change From Baseline in Dynamic Allodynia Intensity at Visits 3 and 6 and Visits 4 and 7 [ Time Frame: Week 3 (Visits 3 and 6) and Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  Five strokes applied with a standardized brush (somedic) across the painful site, 6cm long and at a control site to allow the participants to appreciate any difference. A painful and clearly dysaesthetic (unpleasant) sensation was considered as representing brush allodynia (whereas a "strange" or "tickly" sensation provoked by the brush was not). After each brush stimuli participants were asked to give a pain rating using 11-point numerical rating scale (NRS) where 0=no pain and 10=worst pain imaginable. The average of 5 brush strokes was calculated to obtain the mean score.
  
  
• Mean Change From Baseline in Dynamic Allodynia Area at Visits 3 and 6 and Visits 4 and 7 [ Time Frame: Week 3 (Visits 3 and 6) and Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  Dynamic area brush in cm^2: calculated from 8 measured distances by calculating the area of an octagon. The angle between each pair of lines was 45 degrees at point c. The area of the octagon was found by totaling the areas of the 8 triangles. Octagon with 8 radial lengths from center to the outside. Area = Σ ( ½ length * perpendicular height); Σ ( ½ ri * sin(45) r(i+1) ) = Σ ( (ri * r(i+1) )/2√2)). (where ri, i=1 to 8, were the eight radial lengths)
  
  
• Mean Change From Baseline in Mechanical Pain Sensitivity (Von Frey) at Visits 3 and 6 and Visits 4 and 7 [ Time Frame: Week 3 (Visits 3 and 6) and Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  Sensitivity to mechanical pain stimuli was tested using calibrated Von Frey monofilaments. To obtain a stimulus-response-function, seven different Von Frey monofilaments (size 8 to 512 mN, force increased by a factor of two from filament to filament) applied three times each; each stimulus was participant-rated using 11-point NRS where 0=no pain and 10=worst pain imaginable. If a score of 8 or more was reported for a given intensity no stronger stimuli was applied. Von Frey stimulus was applied to the skin for 1 to 2 seconds. The average of 3 ratings was calculated for the mean score.
  
  
• Mean Change From Baseline in Punctate Allodynia Area (Von Frey) at Visits 3 and 6 and Visits 4 and 7 [ Time Frame: Week 3 (Visits 3 and 6) and Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  Punctate allodynia area in cm^2: calculated from 8 measured distances by calculating the area of an octagon. The angle between each pair of lines was 45 degrees at point c. The area of the octagon was found by totaling the areas of the 8 triangles. Octagon with 8 radial lengths from center to the outside. Area = Σ ( ½ length * perpendicular height); Σ ( ½ ri * sin(45) r(i+1) ) = Σ ( (ri * r(i+1) )/2√2)). (where ri, i=1 to 8, were the eight radial lengths)
  
  
• Mean Change From Baseline in Cold Pain Sensitivity at Visits 3 and 6 and Visits 4 and 7 [ Time Frame: Week 3 (Visits 3 and 6) and Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  Duration of thermal stimuli was 2 seconds and an intensity that is increased in steps of 5 degrees celsius for cold stimuli (between 5 and 20 degrees celsius). Thermal pain sensitivity was participant-rated using 11-point NRS where 0=no pain and 10=worst pain imaginable. The average of 2 ratings was calculated to get the mean score.
  
  
• Mean Change From Baseline in Heat Pain Sensitivity at Visits 3 and 6 and Visits 4 and 7 [ Time Frame: Week 3 (Visits 3 and 6) and Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  Duration of thermal stimuli was 2 seconds and an intensity that is increased in steps of 4 degrees celsius for heat stimuli (between 40 and 50 degrees celsius). Thermal pain sensitivity was participant-rated using 11-point NRS where 0=no pain and 10=worst pain imaginable. The average of 2 ratings was calculated to get the mean score.
  
  

• Mean Change From Baseline in Weekly Pain Score From the Daily Diary at Visits 3 and 6 and Visits 4 and 7 [ Time Frame: Week 3 (Visits 3 and 6) and Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  Daily pain diary: participant-rated pain during the past 24 hours rated on an 11 point NRS scale where 0=no pain and 10=worst possible pain. For a given week, the pain response was the average of the 7 daily entries for that week, or average of the available data for that week if fewer than 7 entries were recorded (>=1 daily pain score for any given week required). The endpoint for each week consisted of the change from baseline in average pain score (follow-up value minus baseline).
  
  
• Mean Change From Baseline in Patient's Global Impression of Change (PGIC) at Visits 3 and 6 and Visits 4 and 7 [ Time Frame: Week 3 (Visits 3 and 6) and Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  PGIC: participant-rated assessment measuring change in participant's overall status on a 7-point scale from 1=very much improved to 7=very much worse.
  
  
• Mean Change From Baseline in Test-Day Global Pain Intensity at Visits 3 and 6 and Visits 4 and 7 [ Time Frame: Week 3 (Visits 3 and 6) and Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  Global pain: participant-rated pain using the test-day global pain scale, consisting of an 11-point NRS where 0 = no pain and 10 = worst possible pain. Participants described intensity of pain in response to "How intense is your pain today?"
  
  
• Mean Change From Baseline in Neuropathic Pain Symptom Inventory (NPSI) Total Score at Visits 4 and 7 [ Time Frame: Week 4 (Visits 4 and 7) of each period ] [ Designated as safety issue: No ]
  NPSI: 10-item self-administered questionnaire assessing 5 dimensions of pain (burning superficial spontaneous pain, pressing deep spontaneous pain, paroxysmal pain, evoked pain, and paresthesia/dysesthesia). Each item consists of a question about the specific qualities of pain and an 11-point numerical scale range: 0 (absence of pain) to 10 (maximum intensity imaginable), and 2 temporal items related to spontaneous and paroxysmal pain. Maximum total score possible = 100.
  
  

Methodology to assess reproducibility and sensitivity of quantitative sensory testing