Determination of Patient Acceptable Symptom State for the Oswestry Disability Index Score in Patients Who Underwent Minimally Invasive Discectomy for Lumbar Disc Herniation: 2-Year Follow-up Data from a Randomized Controlled Trial.

OBJECTIVE:We aim to determinate the patient acceptable symptom state (PASS) for the Oswestry Disability Index (ODI) score in patients undergoing minimally invasive discectomy for the treatment of lumbar disc herniation. METHODS:A post hoc analysis of prospectively collected, 2-year follow-up data was conducted. The anchor for determination of PASS was the European Quality of Life Visual Analog Scales question, and the Pearson correlation test was performed to evaluate its validity. The receiver operating characteristics (ROC) curve analysis was conducted to determine the PASS thresholds for ODI and its discriminative ability assessment. Sensitivity analyses were also carried out for alternative definition of PASS, different follow-up periods, and different subgroups. RESULTS:A total of 222 patients (92.1%) completed the 2-year follow-up, 92.8% of whom considered their state to be acceptable. The area under the ROC curve (AUC) were all >0.8, indicating a high discriminative ability. The PASS threshold for the ODI was suggested to be 5 at 6 months (AUC: 0.80; sensitivity: 79.0%, specificity: 73.7%) and 2 years (AUC: 0.98; sensitivity: 90.3%, specificity: 100%) postoperatively. Despite some variations found in different body mass index and baseline ODI subgroups, sensitivity analysis showed that the above-mentioned threshold was robust. CONCLUSIONS:An ODI of 5 was noted to be the PASS threshold for patients received minimally invasive discectomy for the treatment of LDH. This ODI threshold was robust, and therefore recommended as the ultimate goal of minimally invasive treatment for LDH, which can help to present results of clinical research at an individual level.