Minimum important differences for the patient-specific functional scale, 4 region-specific outcome measures, and the numeric pain rating scale.
METHODS
Multicenter, prospective, longitudinal cohort study.


OBJECTIVE
To investigate the minimum important difference (MID) of the Patient-Specific Functional Scale (PSFS), 4 region-specific outcome measures, and the numeric pain rating scale (NPRS) across 3 levels of patient-perceived global rating of change in a clinical setting.


BACKGROUND
The MID varies depending on the external anchor defining patient-perceived "importance." The MID for the PSFS has not been established across all body regions.


METHODS
One thousand seven hundred eight consecutive patients with musculoskeletal disorders were recruited from 5 physical therapy clinics. The PSFS, NPRS, and 4 region-specific outcome measures-the Oswestry Disability Index, Neck Disability Index, Upper Extremity Functional Index, and Lower Extremity Functional Scale-were assessed at the initial and final physical therapy visits. Global rating of change was assessed at the final visit. MID was calculated for the PSFS and NPRS (overall and for each body region), and for each region-specific outcome measure, across 3 levels of change defined by the global rating of change (small, medium, large change) using receiver operating characteristic curve methodology.


RESULTS
The MID for the PSFS (on a scale from 0 to 10) ranged from 1.3 (small change) to 2.3 (medium change) to 2.7 (large change), and was relatively stable across body regions. MIDs for the NPRS (-1.5 to -3.5), Oswestry Disability Index (-12), Neck Disability Index (-14), Upper Extremity Functional Index (6 to 11), and Lower Extremity Functional Scale (9 to 16) are also reported.


CONCLUSIONS
We reported the MID for small, medium, and large patient-perceived change on the PSFS, NPRS, Oswestry Disability Index, Neck Disability Index, Upper Extremity Functional Index, and Lower Extremity Functional Scale for use in clinical practice and research.
Centre for Musculoskeletal Outcomes Research, Orthopaedic Surgery Section, Department of Surgical Sciences, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
J Haxby
JH
Abbott
John
J
Schmitt
D000328:Adult; D000368:Aged; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D011939:Mental Recall; D008875:Middle Aged; D009140:Musculoskeletal Diseases / Q000503:physiopathology* / Q000534:rehabilitation*; D017063:Outcome Assessment, Health Care / Q000379:methods*; D010147:Pain Measurement / Q000379:methods / Q000592:standards*; D026741:Physical Therapy Modalities; D011446:Prospective Studies; D013997:Time Factors
clinimetrics; functional outcome measure; outcome assessment