Rasch measurement properties of the Pain Medication Questionnaire in persons with spinal cord injury.

STUDY

DESIGN

Secondary analysis of cross-sectional population-based self-report data.

OBJECTIVE

To determine how well the Pain Medication Questionnaire (PMQ) measures risk of pain medication misuse and its precision in separating individuals with spinal cord injury (SCI) into meaningful classification categories.

SETTING

Academic medical center in Southeastern United States.

METHODS

Data were collected from a population-based registry of SCI (n=971). Eligible participants included adults with traumatic SCI with residual effects who were at least 1 year post injury and 18 years of age and who had PMQ data in which they reported active use of pain medication at the time of the study (n=745).

RESULTS

Most items (23/26) of the PMQ contributed to a single unidimensional construct. Rasch analysis results revealed that the rating scale, majority of persons (>93%), and majority of items (20/23) fit the Rasch measurement model. The PMQ demonstrated adequate reliability (person reliability =0.67) and separated persons into two strata-those likely to misuse pain medication and those with low liklihood of misusing pain medication.

CONCLUSIONS

Findings offer a deeper understanding of the measurement properties of the PMQ as a precursor for widespread population-based studies to elucidate the incidence of pain medication misuse in persons with SCI. Results also have important research and clinical implications for commonly used PMQ total score cut-offs, which may misclassify an individual's risk of pain medication misuse.