Differentiation between pain-related interference and interference caused by the functional impairments of spinal cord injury

Abstract

Study design: Face-to-face interview.

Objectives: Pain interference is an important outcome measure in clinical pain trials. However, after spinal cord injury (SCI), interference caused by pain may be difficult to separate from interference caused by the physical impairment. The objective of this study was to determine the ability of the Life Interference subscale of the Multidimensional Pain Inventory, SCI-version (MPI-SCI) to differentiate between pain-related interference and the interference caused by the physical impairments of SCI.

Setting: VA Medical Center and Miami Project to Cure Paralysis, Miami, FL, USA.

Methods: The subscales of the MPI-SCI (Life Interference (LI), Pain Interference with Daily Activities (PA), Performance of General Activities (GA)), pain intensity, Pain Disability Index (PDI), Functional Independence Measure (FIM), Beck Depression Inventory (BDI) and demographic/injury characteristics were assessed in persons with SCI and chronic pain (n=180).

Results: After controlling for age, time since injury and severity of injury, LI subscale was highly correlated with the PA (r=0.58, P<0.001) and PDI (r=0.61, P<0.001) scores. LI subscale was also significantly correlated with pain intensity (r=0.29, P<0.001) and with the BDI (r=0.39, P<0.001). In contrast, LI subscale was not significantly associated with the GA or FIM scores.

Conclusions: Because of the physical impairments associated with SCI, outcome measures specifically evaluating pain interference may be confounded. This study suggests that the LI subscale administered in an interview format is appropriate for measuring pain-specific interference in the SCI chronic pain population.