A SCALE FOR PREDICTING NONPHYSIOLOGICAL CONTRIBUTIONS TO PAIN

Background: Waddell and colleagues have identified a series of nonorga nic signs which may appear in low back pain patients. The occurrence o f these signs helps predict nonphysiological factors in the etiology o f the pain. This study describes the development of the Waddell Equiva lency Scale (WES) which elicits comparable information from patients w ith pain at other sites. Methods: One hundred fifty patients presentin g to a comprehensive pain clinic with low back pain were evaluated by physicians for Waddell signs and by psychologists using the Pain Prese ntation Inventory (PPI) developed by Psychometric Designs Inc. From th ree scales of the PPI, correlation, analysis of variance and multiple regression identified a formula which predicted Waddell signs from the PPI. The study was replicated on a new sample of 150 patients with al most identical results. The two samples were combined, again with high ly similar results. An interpretive scheme was devised for use of the WES scale. Results: The WES score derived from three scales of the PPI predicts the number of Waddell signs elicited from low back pain pati ents. Since it comes from a paper-and-pencil test rather than a physic al examination, it can be used with patients whose pain locus is other than the back. Conclusions: Behavioral expectations and treatment pla ns, a la Waddell, can now be applied to patients with other than low b ack pain. Clinical application of the WES information over a variety o f pain populations will be required to determine the parameters of its usefulness.