Performance-based or self-report measures of physical function: which should be used in clinical trials of hip fracture patients?
OBJECTIVE
To assess the validity, sensitivity to change, and responsiveness of 3 self-report and 4 performance-based measures of physical function: activity measure for postacute care (AM-PAC) Physical Mobility and Personal Care scales, the Medical Outcomes Study 36-Item Short Form Health Survey Physical Function scale (SF-36 PF), the Physical Functional Performance test (PFP-10), the Short Physical Performance Battery (SPPB), a 4-meter gait speed, and the six-minute walk test (6MWT).


METHODS
A prospective observational study of patients after a hip fracture. Assessments were performed at baseline and 12 weeks postenrollment.


METHODS
Inpatient and outpatient rehabilitation facilities in Norway, the United Kingdom, Sweden, Israel, Germany, the United States, Denmark, and Spain.


METHODS
A sample of study participants (N=108) who had a hip fracture.


METHODS
Not applicable.


METHODS
Assessments of validity (known-groups, concurrent, construct, and predictive), sensitivity to change (effect size, standardized response mean [SRM], SE of measure, minimal detectable change (MDC), and responsiveness (optimal operating cut-points and area under the curve) between baseline and 12-week follow-up.


RESULTS
All physical function measures achieved comparably acceptable levels of validity. Odds ratios in predicting patient Global Assessment of Improvement at 12 weeks were as follows: AM-PAC Physical Mobility scale, 5.3; AM-PAC Personal Care scale, 3.6; SF-36 PF, 4.3; SPPB, 2.0; PFP-10, 2.5; gait speed, 1.9; and 6MWT, 2.4. Effect sizes and SRM exceeded 1 SD for all 7 measures. Percent of patients who exceeded the MDC(90) at week 12 were as follows: AM-PAC Physical Mobility scale, 90%; AM-PAC Personal Care scale, 74%; SF-36 PF, 66%; SPPB, 36%; PFP-10, 75%; gait speed, 69%; and 6MWT, 75%. When evaluating responsiveness using the area under receiver operating curves for each measure, all measures had acceptable responsiveness, and no pattern emerged of superior responsiveness depending on the type of measure used.


CONCLUSIONS
Findings reveal that the validity, sensitivity, and responsiveness of self-report measures of physical function are comparable to performance-based measures in a sample of patients followed after fracturing a hip. From a psychometric perspective, either type of functional measure would be suitable for use in clinical trials where improvement in function is an endpoint of interest. The selection of the most appropriate type of functional measure as the primary endpoint for a clinical trial will depend on other factors, such as the measure's feasibility or the strength of the association between the hypothesized mechanism of action of the study intervention and a functional outcome measure.
Latham
Nancy K
NK
Health and Disability Research Unit, Boston University School of Public Health, Boston, MA 02118-2639, USA. nlatham@bu.edu
Mehta
Vinay
V
Nguyen
Allison Martin
AM
Jette
Alan M
AM
Olarsch
Sippy
S
Papanicolaou
Dimitris
D
Chandler
Julie
J
D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D005060:Europe; D005260:Female; D006620:Hip Fractures / Q000534:rehabilitation*; D006801:Humans; D016015:Logistic Models; D008297:Male; D011446:Prospective Studies; D011594:Psychometrics; D012372:ROC Curve; D016032:Randomized Controlled Trials as Topic; D020127:Recovery of Function; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012737:Sex Factors