Metric properties of the ASIA motor score: subscales improve correlation with functional activities.
OBJECTIVE
To apply item response theory (IRT) methods to neurologic and functional scales to determine the value of using American Spinal Injury Association (ASIA) motor subscores and ability estimates, rather than total ASIA motor scores, to predict motor FIM instrument scores.


METHODS
Secondary analysis of prospectively collected data.


METHODS
Model Spinal Cord Injury Systems centers.


METHODS
People with traumatic spinal cord injury (SCI) (N=4338) discharged from inpatient rehabilitation between January 1, 1994, and March 31, 2003.


METHODS
Not applicable.


METHODS
Total discharge motor FIM scores, FIM subscale scores, and IRT-derived ability estimates of motor FIM scores.


RESULTS
Use of separate ASIA upper-extremity and lower-extremity motor scores improved prediction of motor FIM scores over that of total ASIA motor score (R(2) for motor FIM score, .71 vs .59). Use of IRT-based ability estimates derived by applying a 2-parameter graded response model to the raw scores, however, did not improve prediction of motor FIM scores above that of the ASIA motor subscale scores.


CONCLUSIONS
Consistent with the metric properties of the ASIA motor score, and with recent models of disablement, impairment in SCI is more accurately characterized by using separate ASIA upper- and lower-extremity motor scores than by using a single motor score. Use of subscores for impairment should improve prediction of functional abilities and enhance more complex models of disability.
Marino
Ralph J
RJ
Department of Rehabilitation Medicine, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA 19107, USA. Ralph.marino@jefferson.edu
Graves
Daniel E
DE
D000059:Accidents / Q000706:statistics & numerical data; D000203:Activities of Daily Living; D000328:Adult; D000704:Analysis of Variance; D001132:Arm / Q000503:physiopathology; D004185:Disability Evaluation; D016002:Discriminant Analysis; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D007866:Leg / Q000503:physiopathology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009048:Motor Skills; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011594:Psychometrics; D013119:Spinal Cord Injuries / Q000145:classification* / Q000209:etiology / Q000503:physiopathology*; D015599:Trauma Severity Indices; D014481:United States; D014754:Violence / Q000706:statistics & numerical data