Measuring participation in patients with chronic back pain-the 5-Item Pain Disability Index

Abstract

Background context: Of the three broad outcome domains of body functions and structures, activities, and participation (eg, engaging in valued social roles) outlined in the World Health Organization's (WHO) International Classification of Functioning, Disability and Health (ICF), it has been argued that participation is the most important to individuals, particularly those with chronic health problems. Yet, participation is not commonly measured in back pain research.

Purpose: The aim of this study was to investigate the construct validity of a modified 5-Item Pain Disability Index (PDI) score as a measure of participation in people with chronic back pain.

Study design: A validation study was conducted using cross-sectional data.

Patient sample: Participants with chronic back pain were recruited from a multidisciplinary pain center in Alberta, Canada.

Outcome measures: The outcome measure of interest is the 5-Item PDI.

Methods: Each study participant was given a questionnaire package containing measures of participation, resilience, anxiety and depression, pain intensity, and pain-related disability, in addition to the PDI. The first five items of the PDI deal with social roles involving family responsibilities, recreation, social activities with friends, work, and sexual behavior, and comprised the 5-Item PDI seeking to measure participation. The last two items of the PDI deal with self-care and life support functions and were excluded. Construct validity of the 5-Item PDI as a measure of participation was examined using Pearson correlations or point-biserial correlations to test each hypothesized association.

Results: Participants were 70 people with chronic back pain and a mean age of 48.1 years. Forty-four (62.9%) were women. As hypothesized, the 5-Item PDI was associated with all measures of participation, including the Participation Assessment with Recombined Tools-Objective (r=-0.61), Late-Life Function and Disability Instrument: Disability Component (frequency: r=-0.66; limitation: r=-0.65), Work and Social Adjustment Scale (r=0.85), a global perceived participation scale (r=0.54), employment status (r=-0.30), and the Usual Activity domain of the 15D (r=0.50). The expected correlations observed indicating a moderate or strong association provided supporting evidence for the construct validity of the 5-Item PDI as a measure of participation. The Oswestry Disability Index and the 5-Item PDI were also strongly correlated (r=0.70). The 5-Item PDI was associated to a lesser degree with depressive symptoms and resilience, as measured by the Hospital Anxiety and Depression Scale (HADS) (r=0.25) and the Connor-Davidson Resilience Scale (r=-0.28), as would be expected. No statistically significant association was found between the 5-Item PDI and the HADS Anxiety score.

Conclusions: It is important that outcome measures of participation are included in back pain research to gauge the effects of painful spinal conditions and interventions on maintaining valued social roles. A simple, concise measure would be very useful for this purpose in clinical and research settings. The results of this study support the construct validity of the 5-Item PDI as a brief measure of participation in people with chronic back pain. These findings are likely most applicable to those with chronic back pain attending pain clinics and other tertiary centers for care.

Keywords: Back pain; Construct validity; ICF; Measurement; Participation; Social role.