Spinal cord ability ruler: an interval scale to measure volitional performance after spinal cord injury.
METHODS
Retrospective statistical analysis of database.


OBJECTIVE
Spinal cord injury (SCI) clinical trials are challenged to enroll participants, and early trial outcomes have often been equivocal. We hypothesized that a specifically designed novel true linear interval-scaled outcome measure targeted to simultaneously track a broad range of SCI will enable more inclusive enrollment of participants and valid comparisons of functional changes after SCI.


METHODS
To define a single SCI measurement framework, we used items from existing measures. To evaluate linearity and validity of the measure, we used rigorous psychometric Rasch analysis on two data sets from over 2500 traumatic SCI participants (all levels and severities of SCI) within the EMSCI (European Multicenter study about SCI) database.


RESULTS
Volitional performance was found to be the unidimensional construct that would detect and track a treatment effect from a central nervous system-directed therapeutic. Along with early evidence for voluntary neurological control of upper-extremity muscle contractions, volitional performance is best described by goal-directed activities of daily living that are increasingly difficult to re-acquire when activity within more caudal spinal segments is required. Validity of the Spinal Cord Ability Ruler (SCAR) as a linear interval construct was confirmed with Rasch analysis. All measurement items were properly ordered, as well as being precise and stable across clinically relevant groups. Only 5/24 items had some misfit. Targeting was excellent over time after SCI, with few gaps and only modest floor and ceiling effects (3% each).


CONCLUSIONS
SCAR is a quantitative linear measure of volitional performance across an inclusive range of tetraplegic and paraplegic SCI.
ICORD, University of British Columbia and Vancouver General Hospital, Blusson Spinal Cord Centre, Vancouver, British Columbia, Canada.
R
R
Reed
Tigermed-MacroStat LLC, Gaithersburg, MD, USA.
M
M
Mehra
Kessler Institute for Rehabilitation and Rutgers New Jersey Medical School, West Orange, NJ, USA.
S
S
Kirshblum
Trauma Center Murnau, Murnau, Germany.
D
D
Maier
Craig Hospital, Englewood, CO, USA.
D
D
Lammertse
Acorda Therapeutics Inc., Hawthorne, NY, USA.
A
A
Blight
Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany.
R
R
Rupp
Craig H. Neilsen Foundation, Encino, CA, USA.
L
L
Jones
Trauma Center Bayreuth, Bayreuth, Germany.
R
R
Abel
Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany.
N
N
Weidner
Spinal Cord Injury Center, University Hospital Balgrist, University of Zurich, Zurich, Switzerland.
A
A
Curt
ICORD, University of British Columbia and Vancouver General Hospital, Blusson Spinal Cord Centre, Vancouver, British Columbia, Canada.|SCOPE, C/O ASIA Central Office, Richmond, VA, USA.
J
J
Steeves
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002986:Clinical Trials as Topic; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011594:Psychometrics; D012189:Retrospective Studies; D013119:Spinal Cord Injuries / Q000175:diagnosis* / Q000503:physiopathology; D014836:Volition; D055815:Young Adult