Responsiveness of the PROMIS-29 Scales in Individuals With Chronic Low Back Pain

Prospective cohort study.

To evaluate responsiveness and estimate the minimal clinically important differences (MCIDs) for the Patient-Reported Outcomes Measurement Information System-29 (PROMIS-29) scales in individuals with chronic low back pain.

The PROMIS-29 questionnaire assesses seven health-related quality-of-life domains. However, research to evaluate the responsiveness and MCIDs of the PROMS-29 scores in individuals with low back pain is limited.

The study was conducted in physical therapy clinics in Thailand, using validated Thai versions of the study measures. One hundred and eighty-three individuals with chronic low back pain completed the PROMIS-29 at baseline and at 4-weeks follow-up. Perceived change in each domain assessed by the PROMIS-29 scales was assessed at 4 weeks using a 7-point measure of Global Perceived Effect (GPE). Responsiveness of the PROMIS-29 scale scores was evaluated by examining the effect sizes, the standardized response means (SRMs) for change over time, and examining these as a function of the GPE ratings. MCIDs for the scales were estimated by computing a half a standard deviation (SD) and standard error of measurement statistic for each scale.

The mean change scores, effect sizes, and SRMs increased as a function of the GPE ratings. Significant differences in change scores between those who reported that they were very much improved and those who did not improve were found for the PROMIS-29 Pain Intensity, Physical Function, and Anxiety scales. The correlations between changes scores and GPE ratings were mostly weak in magnitude. The MCID estimates computed as 0.50 of a SD unit and as a standard error of measurement showed similar values.

The PROMIS-29 scale scores assessing pain intensity, physical function, and anxiety evidenced the most responsivity in the study sample. The results, when considered in light of the findings from other investigators, support 5.0 points as a reasonable MCID for most of the PROMIS-29 scales. Further studies are needed to determine the generalizability of the findings.Level of Evidence: 2.