The goal of this study was to determine an appropriate mapping between the Neck Disability Index (NDI) and Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference (PI). Patients undergoing cervical spine surgery may need help to make sense of the NIH PROMIS scores, a global outcome metric with unclear clinical implications. Therefore, researchers established a formula for converting scores on a disease-specific legacy instrument (NDI) to PROMIS PI to ascertain the degree to which the two instruments are correlated and provide criteria for what constitutes a minimal and substantial impairment. Participants were adults who had surgery on their cervical spine at a single institution between 2016 and 2018. No patients who were scheduled to have surgery for trauma-related instability were considered. Information gathered via preoperative questionnaires included patient demographics, the patient’s presenting complaint (such as radiculopathy, myelopathy, or myeloradiculopathy), and procedural details. Patients were included in the study if they had filled out both the NDI and the PROMIS PI, and then correlation and regression analyses were conducted. The study included 196 patients who met all of the requirements. Ages ranged from 56.9±12.9 years on average. There was a correlation between the 2 measures, with a mean NDI of 68.6±38 and a mean PROMIS PI of 60.9±7.3. When comparing the PROMIS PI to the NDI, there was a significant positive correlation (r=0.76, P<0.001). The following formula was derived from linear regression analysis: PROMIS PI=51.042+0.289*NDI(R2=0.57). Investigators conducted a regression study to facilitate the translation of PROMIS PI scores into NDI. Their findings confirmed prior research findings, demonstrating a significant correlation between PROMIS PI and NDI. Significant impairment (NDI=50) was associated with a PROMIS PI score of 66 or higher, while minor relative impairment (NDI=28) was associated with a score of 59 or lower. As PROMIS reporting becomes increasingly commonplace in the scientific literature, these findings will serve as a valuable reference point.
