Numeric Pain Rating Scale

Chronic Musculoskeletal Pain: (Salaffi et al, 2004; n = 825 patients with chronic musculoskeletal pain)

• 1 point or 15.0% change

Shoulder Pain: (Michener et al., 2011; n = 136; surgical and non-surgical conditions; mean age 51.7(16.4) years; 76.5% no surgery,23.5% status post surgery; assessment of average NPRS scores for at rest, normal activity, and strenuous activity)

• 2.17 points for surgical and non-surgical subjects after 3-4 weeks of rehabilitation 

Chronic Pain: (Farrar et al, 2001; n = 2,724 subjects with varying diagnoses including fibromyalgia, diabetic neuropathy, post-herpetic neuralgia, chronic low back pain and osteoarthritis)

• 1.7 points or a reduction of 27.9% (raw change/baseline x 100)

Chronic Pain: (Jensen & McFarland, 1993; n = 200; mean age = 43.83 (13.2) years; mean time since pain onset = 6.13 (8.24) years)

• Adequate test-retest reliability for a single pair of assessments (one assessment during week 1, one assessment during week 2) (r = 0.63)
• Excellent test-retest reliability for ratings on 2 or more days during week 1 compared to 2 or more days during week 2 (r = 0.79 – 0.92)
• Test-retest reliability increases with increasing numbers of ratings with the highest reliability for 4 ratings/day taken on 7 days (r=0.95)

Chronic Pain: (Jensen & McFarland, 1993)

• Excellent internal consistency for a single pair of ratings (one during week 1 and one during week2) (Coefficient alpha = 0.84)
• Excellent internal consistency for ratings on 2 or more days during week 1 compared to 2 or more days during week 2 (Coefficient alpha = 0.89 –0.98)

Shoulder Pain: (Michener et al., 2011)

• Large effect size for surgical (ES = 1.51) and non-surgical subjects (ES = 1.94)

Chronic SCI: (Hanley et al, 2006a; n = 82; mean age = 41.44 (10.14) years; 54% cervical SCI, 38% thoracic SCI, 7% lumbar/sacral SCI; average pretreatment pain intensity = 5.27 (1.79) on NPRS)

• 1.80 points or 36%

Traumatic Spinal Cord Injury (SCI): (Forchhemier MB et al, 2011; n = 6096; mean age = 32.5 (14) years; mean time since injury = 9.8 (9.3) years; all subjects had SCI and pain; injury level: 24.3% AIS D, 5.8% paraplegia AIS C, 5.0% paraplegia B, 29.8% paraplegia A, 7.0% tetraplegia AIS C, 8.0% tetraplegia AIS B, 20.1% tetraplegia AIS A)

• Pain severity can be categorized into 3 distinct groups as relates to pain interference: 1-3, 4-6, and 7-10 

Chronic SCI: (Hanley et al, 2006b; for questions about general pain: n = 307, mean age = 43.1 (13.0) years; for questions about worst pain: n = 174, mean age = 41.6 (13.6) years; inclusion criteria of SCI >6 months)

• For rating overall pain: mild = 1-3, moderate = 4-7, severe = 8-10 
• For rating worst pain problem: mild = 1-3, moderate = 4-6, severe = 7-10
• For cut-off determination, pain severity on NPRS was compared to pain interference

Convergent Validity:

Traumatic SCI: (Dijkers, 2010; n = 168; mean 38(18) years; level of injury: 10% paraplegia incomplete, 26% paraplegia complete, 45% tetraplegia incomplete, 19% tetraplegia complete)

• Adequate correlation between NPRS and Verbal Rating Scale (Spearman’s r = 0.38)

SCI: (Bryce et al, 2007; n = 50 health care providers attending the 2006 combined American Spinal Injury Association (ASIA)/International Spinal Cord Society (ISCoS) scientific meeting)

• In a vote on the validity and usefulness of the NPRS in people with pain related to a SCI, attendees voted as follows: 
  • 64% NPRS is a valid measure and should be part of a minimum dataset for clinical trials 
  • 14% NPRS is a valid measure but should be part of an expanded dataset only 
  • 20% NPRS needs further study to establish reliability and validity before being recommended 
  • 2% NPRS is not valid or relevant for use 
  • 79% NPRS as first choice for a minimum data set over a VRS (16%) and VAS (5%) (n= 57)

Post-operative Patients: (Sloman et al, 2006; n = 150; mean age = 47.2 years; 56% post-abdominal surgery, 28.6% post-orthopedic surgery, 15.4% other types of surgery) 

• Percent change in NPRS rather than raw score change may provide more meaningful information regarding a patient’s response to pain treatment. For example, a change from 3/10 pain to 0/10 pain may be more meaningful than a change from 8/10 pain to 5/10 pain. 
• Therefore, MCIDs were determined in percent change: 
  • 35% reduction on the NPRS had a rating of “minimal relief” 
  • 67% reduction had a rating of “moderate relief” 
  • 70% reduction had a rating of “much relief” 
  • 94% reduction had a rating of “complete relief”

Hospital/Emergency Room Population: (Bijur et al, 2003; n = 108; mean age = 44 years; participants presented with acute pain in the emergency room department)

• 1.3 points

Healthy Populations: (Herr et al, 2004; n = 175 total, 86 subjects aged 25-55 years (mean age = 39.1 (8.8) years), 89 subjects aged 65-94 years (mean age = 76.0 (7.4) years)) 

• Excellent interrater reliability with 100% agreement between two raters scoring the 0-10 point NPRS

Healthy Populations: (Herr et al, 2004)

• Excellent internal consistency for NPRS in participants aged 65-94 (Cronbach’s alpha = 0.87) 
• Excellent internal consistency for NPRS in participants aged 25-55 (Cronbach’s alpha = 0.88)

Concurrent Validity:

Healthy Populations: (Herr et al, 2004)

• Excellent correlation between NPRS and Visual Analogue Scale (r = 0.86)
• Excellent correlation between NPRS and Verbal Descriptor Scale (r = 0.88)
• Excellent correlation between NPRS and 21-point Numeric Rating Scale (r = 0.87) 
• Excellent correlation between NRPS (on 0-20 scale) and Faces Pain Scale (r = 0.80)

Convergent Validity: 

Hospital/Emergency Room Population: (Bijur et al, 2003) 

• Excellent correlation between NRPS and VAS (r = 0.94, 95% CI = 0.93-0.95)

Healthy Population: (Herr et al, 2004)

• Subjects were shown 5 scales rating pain intensity and asked which scale best described the severity of pain experienced during the study. 
  • 35.3% preferred the 21-point Numeric Rating Scale (written format) 
  • 25.3% preferred the Verbal Descriptor Scale 
  • 15.9% preferred the NPRS (11-point verbal scale) 
  • 12.9% preferred the Faces Pain Scale 
  • 10.6% preferred the Visual Analogue Scale

Healthy Population: (Herr et al, 2004)

• NPRS detected significant differences across temperatures of thermal stimuli tested (F6,1037 = 67.09

Lower Back Pain: (Childs et al, 2005; n = 131; mean age = 33.9 (11) years; patients receiving physical therapy; 87% with symptoms for under 6 weeks)

• SEM = 1.02

Lower Back Pain: (Childs et al, 2005)

• 2 points based on a 95% confidence interval

Lower Back Pain: (Childs et al, 2005)

• At 1 week of physical therapy treatment = 1.5 points
• At 4 weeks of physical therapy treatment = 2.2 points

Lower Back Pain: (Childs et al, 2005)

• Large effect size at 1 week and 4 weeks (ES = 0.95-1.2) in patients receiving physical therapy for low back pain