Validity of the Modified Defense and Veterans Pain Rating Scale Supplemented With Items Germane to Total Joint Replacement: Secondary Analysis From a Randomized Trial.

ABSTRACT

INTRODUCTION: Valid measures of pain are helpful to adjust treatment plans in real time after total joint replacement (TJR). We enhanced the existing Defense and Veterans Pain Rating Scale (DVPRS) with items related to pain at rest and movement, in specific reference to operative and nonoperative joints, creating the TJR-DVPRS. This manuscript is presented to validate the modified survey instrument. The aims of this psychometric study were to evaluate (1) the latent structure of the TJR-DVPRS, (2) the relationships among the pain dimensions represented on the TJR-DVPRS and the reference-standard Short-Form McGill Pain Questionnaire (version 2, SF-MPQ-2), and (3) the responsiveness of these two measures before and after TJR. MATERIALS AND METHODS: This report involves a secondary analysis of pain surveys from 135 veterans undergoing TJR at one center who participated in a randomized trial. The study was approved by the institutional review boards from participating institutions. The TJR-DVPRS and SF-MPQ-2 were completed preoperatively, during postoperative day 1, and 6 weeks post-surgery. Standard psychometric evaluations included correlations, principal component analysis, and internal consistency of survey items and subscales, using preoperative baseline data as a frame of reference. Responsiveness analysis included assessing both effect size and thresholds of clinically important change for survey subscales using data from all three time points. RESULTS: Two reliable subscales were identified for the TJR-DVPRS, one including items about pain intensity and interference related to the operative joint (Cronbach's α = .809) and the other including two pain items on the nonoperative joint. Combining the subscales indicated a two-factor solution The first valid factor entailed the four subscales of the SF-MPQ-2 and the TJR-DVPRS operative joint subscales, indicating that these subscales validly represent the same pain dimension. The second valid factor entailed the TJR-DVPRS subscale addressing the nonoperative joint. Responsiveness analysis following accepted psychometric methods demonstrated significant decreases in pain from the preoperative period to 6 weeks postoperatively for all subscales. The TJR-DVPRS and SF-MPQ-2 subscales were similarly responsive, except for the SF-MPQ-2 neuropathic and TJR-DVPRS nonoperative joint subscales, which were minimally responsive during the preoperative to 6-week period. CONCLUSIONS: The TJR-DVPRS is valid for use among veterans undergoing TJR and poses significantly less respondent burden than does the SF-MPQ-2. The brevity and ease of use of the TJR-DVPRS make it a practical tool for use during surgical recovery to monitor pain intensity at rest and with movement in the operative joint, and to assess pain interference with activity, sleep, and mood. The TJR-DVPRS is at least as responsive as the SF-MPQ-2, but the SF-MPQ-2 neuropathic and TJR-DVPRS nonoperative joint subscales were minimally responsive. Limitations of this study include the small sample size, under-representation of women (which would be expected in the veteran population), and using only veterans. Future validations studies should include civilians and active military TJR patients.