VALIDITY OF THE CENTRAL SENSITIZATION INVENTORY IN PATIENTS WITH KNEE OSTEOARTHRITIS

Abstract

Osteoarthritis is the 12th leading cause of years lived with disability globally and by 2040 more than 10 million Canadians will have knee osteoarthritis (KOA). Pain in persons with KOA is well-recognized, persistent and chronic with central sensitization (CS) being prevalent in ~30%. CS is measured by psychophysical testing and patient-reported methods such as the Central Sensitization Inventory (CSI). The CSI was developed using subgroups of people with chronic pain, but not those with KOA. Therefore, validity of the CSI in people with KOA is lacking. CS as indicated by psychophysical tests is associated with CSI scores lower than the recommended cut score. Therefore, we aimed to evaluate the validity of the CSI through Rasch analysis in persons with KOA. We then sought to determine the agreement of the Rasch calibrated (RC-CSI) version of the CSI with the original and to evaluate the validity of the RC-CSI with psychophysical tests in people with KOA. In the first study, the CSI was able to fit Rasch model. After iterative analysis, we found the CSI to be a singular construct with acceptable unidimensionality while retaining all 25 items. Only two items - frequent urination (item 21) and Skin problems (item 19) showed a pattern of uniform differential item functioning by age and sex respectively. Moreover, we generated a RC-CSI cut score of 31.37 that we used to compare with the original cut score of 40. In second study, the findings suggested a lack of agreement between the two versions of the CSI demonstrating small bias. When exploring sensitivity and specificity with psychophysical tests, the RC-CSI showed little clinical value over the original CSI. We therefore recommend that the original CSI should be used with individual clients as our preliminary findings suggest that there is no added benefit to using the RC- CSI.