Support for the Reliability and Validity of the National Institutes of Health Impact Stratification Score in a Sample of Active-Duty U.S. Military Personnel with Low Back Pain

Objective

Evaluate the Impact Stratification Score (ISS) measure of low back pain impact that assesses physical function, pain interference, and pain intensity.

Design

Secondary analyses of a prospective comparative effectiveness trial of active-duty military personnel with low back pain.

Setting

A Naval hospital at a military training site (Pensacola, Florida) and two military medical centers: 1) Walter Reed National Military Medical Center (Bethesda, Maryland); and 2) San Diego Naval Medical Center.

Subjects

The 749 active-duty military personnel had an average age of 31 years, 76% were male, and 67% were white.

Methods

Participants completed questionnaires at baseline, 6 weeks later, and 12 weeks later. Measures included the ISS, Roland-Morris Disability Questionnaire (RMDQ), PROMIS-29 v1.0 satisfaction with social role participation scale, and single-item ratings of average pain, feeling bothered by low back pain in the past week, and a rating of change in low back pain.

Results

Internal consistency reliability for the ISS was 0.92-0.93 at the three time points. The ISS correlated 0.75 to 0.84 with the RMDQ, 0.51 to 0.78 with the single-item ratings, and -0.64 to -0.71 with satisfaction with social role participation. The ISS was responsive to change on the three single items. The area under the curve for the ISS predicting improvement on the rating of change from baseline to 6 weeks later was 0.83.

Conclusions

This study provides support for the reliability and validity of the ISS as a patient-reported summary measure for acute, subacute, and chronic low back pain. The ISS is a useful indicator of low back impact.