What PROMIS Scores Correlate With Severe Disability in Cervical Spine Surgery?

Study Design: Institutional Review Board-approved prospective cohort study. Objectives: To establish a conversion between Neck Disability Index (NDI) and Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference (PI). Summary of Background Data: As the National Institutes of Health (NIH) PROMIS is a global outcome measure, it can be difficult to interpret the clinical implications in patients with cervical spine surgery. To determine how a disease-specific legacy instrument (NDI) correlates with PROMIS PI and define levels of substantial and minimal disability, we developed a formula to convert NDI scores to PROMIS PI. Materials and Methods: Adult patients undergoing cervical spine surgery at a single institution from 2016 to 2018 were prospectively enrolled. Patients undergoing surgery for instability due to trauma were excluded. Preoperative questionnaires, demographic data, presenting complaint (radiculopathy, myelopathy, myeloradiculopathy), and procedural data were recorded. Patients were included if they had completed the NDI and PROMIS PI. Correlation and regression analyses were performed. Results: One hundred ninety-six patients met inclusion criteria. The average age was 56.9±12.9 years. The mean NDI score was 68.6±38 and PROMIS PI was 60.9±7.3. The PROMIS PI was strongly correlated with the NDI (r=0.76, P<0.001). Linear regression analysis revealed the following formula: Conclusions: We performed a regression analysis allowing for the conversion of PROMIS PI scores with NDI. In keeping with the previous studies, our analysis showed that PROMIS PI was most strongly correlated to NDI. A PROMIS PI score >66 was correlated to substantial disability (NDI=50), whereas a PROMIS PI score <59 was correlated to minimal relative impairment (NDI=28). These results provide important reference, as PROMIS reporting becomes more widespread in the literature.