Objective

To develop brief, flexible, and sound measures of pain catastrophizing and pain-related self-efficacy for people living with chronic pain

Study Design

An item bank is a set of items calibrated using Item Response Theory (IRT) that ask about a specific topic. Users can create custom short forms by picking sets of questions from an item bank or by using computerized adaptive testing. In this study, researchers developed separate item banks to measure pain catastrophizing and pain-related self-efficacy. Pain catastrophizing is a tendency to worry excessively about pain and to feel helpless about coping with it. Pain-related self-efficacy is the belief of people living with chronic pain that they can live well despite that pain. Existing measures of pain catastrophizing and pain-related self-efficacy were created using older methodology requiring all respondents to answer the same items. In this study, patient advisors, pain researchers, and clinicians guided item-bank development and provided feedback throughout the study.

The researchers developed the new item banks using qualitative and quantitative methodologies from the Patient-Reported Outcomes Measurement Information System (PROMIS®), including IRT, which result in flexible, brief, and clinically meaningful measures. To define the two aspects of living with chronic pain, the researchers worked with patient advisors, pain researchers, and clinicians. Then, focus group participants living with chronic pain provided feedback on the definitions and the items used to measure pain catastrophizing and pain-related self-efficacy. Using this feedback, the researchers developed items and tested them in interviews with people living with chronic pain.

Finally, the researchers conducted a field test of the item banks with 795 people living with chronic pain across the country. Of these people, 86% were white, 9% were African American, and 5% were other races. The average age was 55 and 64% were female. Respondents had a variety of chronic pain conditions such as low back pain and pain from multiple sclerosis.

To develop a scoring system and evaluate the reliability and validity of the scores, researchers conducted psychometric analyses. After finalizing the item banks, the team developed two- and six-question short forms for both pain catastrophizing and pain-related self-efficacy and calculated the correlations between the short forms and the full item banks. To evaluate test-retest reliability, the researchers examined the correlations between the scores of respondents who completed the measure a second time 40 to 80 hours later.

Results

Pain Appraisal Scale. The researchers renamed the pain-catastrophizing measure the Pain Appraisal Scale because focus group participants found the term stigmatizing. The final item bank included 24 questions. Scores from the 24-question item bank correlated highly with the two-question (r=0.71) and six-question (r=0.99) short forms. Test-retest reliability was high for the full bank (intraclass correlation [ICC]=0.93), two-question (ICC=0.85), and six-question (ICC=0.91) short forms. The item-bank scores correlated highly with the legacy Pain Catastrophizing Scale (r=0.83), supporting construct validity. Patients with mild, moderate, and severe pain had significantly different scores (p<0.05), supporting known groups validity.

Pain-related self-efficacy item bank. The final item bank included 29 questions. Scores from the full item bank correlated highly with the two-question (r=0.90) and six-question (r=0.97) short forms. Test-retest reliability was high for the full bank (ICC=0.95), two-question (ICC=0.86), and six-question (ICC=0.92) short forms. The item-bank score correlated highly with the legacy Pain Self-Efficacy Questionnaire (r=0.87), supporting construct validity. Patients with mild, moderate, and severe pain had significantly different scores (p<0.05).

Limitations

The study did not include many people with common pain conditions such as carpal tunnel or cancer-related pain. The item banks may not be valid for people with these conditions.

Conclusions and Relevance

Results support the reliability and validity of the pain appraisal and pain-related self-efficacy item banks and short forms. Epidemiologists and researchers can use the measures to examine predictors and correlates of health outcomes related to chronic pain.

Future Research Needs

Future research could include additional validity studies with people of different races or ages, or with other types of pain. Researchers could also determine and validate cutoff scores for use in clinical practice and determine what changes in scores are clinically important.