Study Supports Validity of PLUS-M

A team of researchers from the University of Washington and the Miami Veterans Affairs Healthcare System, Florida, collaborated to assess the construct validity of the Prosthetic Limb Users Survey of Mobility (PLUS-M), a self-report mobility measure for people with lower-limb amputations. The evidence indicates that PLUS-M has good construct validity among this patient population, according to the study's authors. The study was published August 30 in the Archives of Physical Medicine and Rehabilitation.

The researchers conducted a cross-sectional study with a cohort of 199 lower-limb prosthesis users (mean age = 55.4 ± 14.3 years, 71.4 percent male) from 37 private prosthetic clinics in the United States. The participants were assessed before receiving a replacement prosthesis, prosthetic socket, and/or prosthetic knee. Convergent construct validity was examined using correlations between participants' PLUS-M T-scores and measures of physical function, mobility, and balance. Known-groups construct validity was evaluated by comparing differences in PLUS-M T-scores among participants grouped by Medicare Functional Classification Levels (MFCLs).

PLUS-M T-scores demonstrated a moderate positive relationship with Amputee Mobility Predictor scores (rs = 0.54, p < 0.001) and a moderate negative relationship with Timed Up and Go test times (rs = -0.56, p < 0.001). The PLUS-M also showed a strong positive relationship with Prosthesis Evaluation Questionnaire-Mobility Subscale scores (rs = 0.78, p < 0.001), Activities-specific Balance Confidence Scale scores (rs = 0.81, p < 0.001), and Patient Reported Outcomes Measurement Information System-Physical Function T-scores (rs = 0.81, p < 0.001). Significant differences (p < 0.05) in PLUS-M T-scores were found among groups of people classified by different MFCLs.

Given these results, the researchers conclude that the PLUS-M is a valid self-report measure of prosthetic mobility. Correlations between PLUS-M and measures of physical function, mobility, and balance indicate convergent construct validity, and significant differences in PLUS-M T-scores across MFCL groups provide evidence of known-groups construct validity.