A method to provide a more efficient and reliable measure of self-report physical work capacity for patients with spinal pain.

Self-report measures of functional ability are commonly used in occupational rehabilitation to measure the current status of an individual and his or her progress in response to intervention. Most of these measures have been developed using classical test theory that does not provide calibration of the items. Methods of test development that originated in the field of Education have been applied recently to healthcare measures, providing item calibration and allowing proportional evaluation of total scores. The purpose of this article is to demonstrate the application of these methods in the revision of an existing self-report measure. The potential value of these methods to improve established measures is demonstrated.