Measurement precision of the Pain Catastrophizing Scale and its short forms in chronic low back pain.

The Pain Catastrophizing Scale (PCS) is a widely studied tool to assess pain catastrophizing for chronic low back pain (LBP). Short forms of the PCS exist, but their measurement precision at individual level is unclear. This study aimed to analyze the Rasch psychometric characteristics of the PCS and three of its short forms (two 4-item and one 6-item) in a sample of 180 Italian-speaking patients with chronic LBP, and compare their measurement precision at the individual level. We performed a Rasch analysis on each version of the PCS and calculated test information functions (TIFs) to examine conditional measurement precision. Rasch analysis showed appropriate rating category functioning, unidimensionality, and acceptable fit to the Rasch model for all PCS versions. This represented a prerequisite for performing further advanced psychometric analyses. According to TIFs, the PCS full scale showed-at any score level-higher measurement precision in estimating individual pain catastrophizing than its short forms (which had unacceptably high standard errors of measurement). Our results show acceptable conditional precision of the PCS full scale in estimating pain catastrophizing. However, further studies are needed to confirm its diagnostic accuracy at individual level. On the other hand, the study warns against use of the three PCS short forms for clinical decision-making at the individual level.