A questionnaire for grading pain, the chronic pain grade questionnaire (CPG), 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 ICF identifies 3 major outcomes in chronic pain: impairment, restriction of activities, and restrictions in participation. The CPG, the earlier questionnaire uses 5 grades: 1- pain free, 2- low disability and low intensity, 3- low disability/high intensity, 4- high disability/moderately limiting, and 5- high disability/severely limiting.
There are 7 questions in the CPG:
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’?
Twelve people participated in this study, 3 were doctors who were involved in pain research and the others were academic researchers. They received the questionnaire by mail and, after reading an explanation of the tasks, they matched items to definitions, according to their interpretations. When the researchers put the participants’ answers together, they found the CPG measured all the ICF outcomes.
A method of measuring how valid the content is of a health outcome measure, such as ICF, has been developed. Called the Discriminant Content Validation (DCV), it examines the relationship between the individual items that are being measured and what they say they will measure. Using the DCV, the authors found that Questions 1, 2, and 3 of the CPG looked at impairment; Questions 4 and 7 looked at both activity limitations and participation restrictions; Question 5 looked at activity limitations alone; and Question 6 looked at participation restrictions alone.
The authors concluded that although the ICF hasn’t been used very much yet in the literature, the study findings show it could allow doctors and researchers to tailor it to specific requirements, while still maintaining the same standards of care.