Chronic Pain Grade Scale (CPGS)
Chronic pain grade questionnaire (CPG),a questionnaire for grading pain, was established several years ago before the publication of the World Health Organization's International Classification of Functioning Disability and Health (ICF). The purpose of the ICF was to give doctors a standard with which to work when comparing pain and health. The researchers in this study wanted to see if the two could be used together in assessing pain and disability. 
The CPGS is a multidimensional measure that assesses 2 dimensions of overall chronic pain severity: pain intensity and pain-related disability. It is suitable for use in all chronic pain conditions, including chronic musculoskeletal (MSK) and low back pain 
Subscale scores for pain intensity and disability are combined to calculate a chronic pain grade that enables classification of chronic pain patients into 5 hierarchical categories: grades 0 (no pain) to IV (high disability-severely limiting) .
The CPGS is comprised of 7 items:
1- How would you rate your pain on a 0-10 scale at the present time, this is right now, where 0 is 'no pain' and 10 is 'pain as bad as it could be'?
2- In the past 6 months, how intense was your worse pain rated on a 0-10 scale (rated as above)?
3- In the past 6 months, on average, how intense was your pain rated on a 0-10 scale (rated as above)? (That is your usual pain at times you were experiencing pain.)
4- About how many days in the last 6 months have you been kept from your usual activities (work, school, housework) because of this pain?
5- In the past 6 months, how much has this pain interfered with your daily activities on a 0-10 scale where 0 is 'no interference' and 10 is 'extreme change'?
6- In the past 6 months, how much has this pain changed your ability to take part in recreational, social, and family activities where 0 is 'no change' and 10 is 'extreme change'?
7- In the past 6 months, how has this pain changed your ability to work (including housework) where 0 is 'no change' and 10 is 'extreme change'?
Pain in the past 3–6 months
Obtaining the Scale
The scale is available in the original reference , as well as directly from the author.
The CPGS is an interview-administered questionnaire that can also be self-completed by respondents 
All items are scored on an 11-point Likert scale, with responses ranging from 0–10. Scores are calculated for 3 subscales: the characteristic pain intensity score, which ranges from 0–100, is calculated as the mean intensity ratings for reported current, worst, and average pain; the disability score, which ranges from 0–100, is calculated as the mean rating for difficulty performing daily, social, and work activities; and the disability points score, which ranges from 0–3, is derived from a combination of ranked categories of number of disability days and disability score. 
The 3 subscale scores (characteristic pain intensity, disability score, and the disability points score) are used to classify subjects into 1 of the 5 pain severity grades: grade 0 for no pain, grade I for low disability-low intensity, grade II for low disability-high
intensity, grade III for high disability-moderately limiting, and grade IV for high disability-severely limiting.
Merits and Demerits
- The CPGS is a valid and reliable tool that is useful for the evaluation of chronic MSK pain
- It allows for grading of the global severity of chronic pain and therefore analysis of the qualitative changes in chronic pain over time
- Further, the CPGS assesses not only aspects of the pain itself, but also the impact of the pain on daily,
social, and work activities, which is a significant advantage over many other pain questionnaires
- Time to complete the CPGS does not exceed 10 minutes
- Easy to administer
- The CPGS has been adapted into UK English . An Italian version has been developed to evaluate severity in chronic pain patients .
- A limitation of the CPGS relative to the other scales is the complexity of scoring
- Additionally, further research is needed to be able to compare scoring methods and cut points
Interviews were conducted with primary care patients with back pain, headache, and temporomandibular disorder . The development of the graded classification drew on concepts by Turk and Rudy of chronic pain severity  . Two of the items used in the disability score were adapted from their Multidimensional Pain Inventory . The Guttman scaling method was used to develop the graded classification of chronic pain .
The CPGS is easy to understand and complete based on a high response rate (76.3%) to a postal survey sent to general practice patients in the UK . Among MSK chronic pain patients, missing values were only noted in<3% of each of the questions in an Italian version of the CPGS .
For internal consistency, Cronbach’s alpha was shown to be = 0.74 among patients with chronic back pain . In an Italian version of CPGS, Cronbach’s alpha ranged from 0.81–0.89 for subscales and global scores in patients with chronic MSK pain . In UK general practice patients with low back pain, test–retest reliability was high after a 2-week interval.
For construct validity, cross-sectional and longitudinal studies of general practice patients have shown that higher scores on the CPGS, indicating greater chronic pain, are significantly associated with higher rates of unemployment, greater pain impact scale scores, greater use of opioid analgesics and physician visits, depressed mood, and lower self-rated health status   . Comparisons of CPGS scores with the Short Form 36 Health Survey (SF-36) indicate that a higher chronic pain grade using the CPGS is associated with poorer physical, psychological, social, and general health as measured by the SF-36 (P= 0.001)  and worse scores on the SF-36 bodily pain scale (p = 0.545,P<0.0001) (95). Spearman’s correlation coefficients for the CPGS scores and the various dimensions of SF-36 were highest for the pain dimension (r = -0.71 to -0.84) and lowest for the mental health dimension (r=-0.28 to-0.38) .
Ability to detect change
Among patients with moderate to severe chronic MSK pain, the CPGS has been shown to be modestly responsive to changes after 12 months of treatment with an efficacious pain intervention, with standardized effect sizes for the intensity and disability sub-scales of 0.41 and 0.43, respectively. Among participants with chronic knee or hip pain, the standardized effect size for the CPGS intensity was 0.32 .
- Diane Dixon, Beth Pollard, and Marie Johnston. What does the chronic pain questionnaire measure? In Pain. July 2007. Vol. 130. Pp. 249-253. available at: http://www.spineuniversity.com/chronic_pain_grade_questionnaire_combines_with_international_classification_of_functioning_disability
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