Construct validity of the physical function scale of the Swiss Spinal Stenosis Questionnaire for the measurement of walking capacity.
METHODS
Measurement (validity) study using data from a prospective longitudinal study of lumbar spinal stenosis.


OBJECTIVE
Provide convergent and divergent validity evidence for the use of the Physical Function Scale of the Swiss Spinal Stenosis Questionnaire for the measurement of walking capacity in persons with lumbar spinal stenosis. We were also interested in the association between the Physical Function Scale and the Oswestry Disability Index (ODI).


BACKGROUND
The Physical Function Scale has been used to assess walking capacity in persons with lumbar spinal stenosis; however, there have been limited studies investigating its psychometric properties. No validity studies have compared the Physical Function Scale and the ODI head to head.


METHODS
The Physical Function Scale was correlated with the ODI, Health Utilities Index, Centres for Epidemiologic Studies Depression Scale, Medical Outcomes Survey Social Support Scale, and an additional item from the Oxford Claudication Score.


RESULTS
As hypothesized, the Physical Function Scale was correlated highly with those instruments and items intended to measure walking capacity and minimally with those instruments intended to measure different constructs. The correlation between the Physical Function Scale and the ODI was r = 0.719.


CONCLUSIONS
Results support construct validity of the Physical Function Scale for the measurement of walking in an lumbar spinal stenosis population. However, it cannot be ascertained from the current study that the construct being measured is, indeed, walking capacity. Further research is warranted to investigate criterion validity evidence for the use of the Physical Function Scale in the measurement of walking capacity in lumbar spinal stenosis, by examining the relationships between self-report and observational measures of walking.
Tomkins
Christy C
CC
Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada. ctomkins@ualberta.ca
Battié
Michele C
MC
Hu
Richard
R
D000368:Aged; D002170:Canada; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000209:etiology* / Q000503:physiopathology / Q000601:surgery; D010147:Pain Measurement; D011446:Prospective Studies; D011594:Psychometrics; D020127:Recovery of Function; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013130:Spinal Stenosis / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D016138:Walking