Spinal Instability Neoplastic Score: An Analysis of Reliability and Validity From the Spine Oncology Study Group

TLDR

Standardized indications for treating tumor‑related spinal instability are limited by the absence of a valid and reliable classification system. The study aimed to assess the inter‑observer and intra‑observer reliability and predictive validity of the Spinal Instability Neoplastic Score (SINS). Thirty spinal tumor cases were evaluated by Spine Oncology Study Group members who scored each case twice with SINS, used the consensus median as the gold standard, and converted total scores into stable, potentially unstable, and unstable categories. SINS demonstrated near‑perfect inter‑observer (κ 0.79–0.84, ICC 0.85) and intra‑observer (κ 0.81–0.86, ICC 0.89) reliability, a predictive validity κ of 0.71, and 95.7% sensitivity with 79.5% specificity for identifying potentially unstable or unstable lesions.

Abstract

Standardized indications for treatment of tumor-related spinal instability are hampered by the lack of a valid and reliable classification system. The objective of this study was to determine the interobserver reliability, intraobserver reliability, and predictive validity of the Spinal Instability Neoplastic Score (SINS).Clinical and radiographic data from 30 patients with spinal tumors were classified as stable, potentially unstable, and unstable by members of the Spine Oncology Study Group. The median category for each patient case (consensus opinion) was used as the gold standard for predictive validity testing. On two occasions at least 6 weeks apart, each rater also scored each patient using SINS. Each total score was converted into a three-category data field, with 0 to 6 as stable, 7 to 12 as potentially unstable, and 13 to 18 as unstable.The κ statistics for interobserver reliability were 0.790, 0.841, 0.244, 0.456, 0.462, and 0.492 for the fields of location, pain, bone quality, alignment, vertebral body collapse, and posterolateral involvement, respectively. The κ statistics for intraobserver reliability were 0.806, 0.859, 0.528, 0.614, 0.590, and 0.662 for the same respective fields. Intraclass correlation coefficients for inter- and intraobserver reliability of total SINS score were 0.846 (95% CI, 0.773 to 0.911) and 0.886 (95% CI, 0.868 to 0.902), respectively. The κ statistic for predictive validity was 0.712 (95% CI, 0.676 to 0.766).SINS demonstrated near-perfect inter- and intraobserver reliability in determining three clinically relevant categories of stability. The sensitivity and specificity of SINS for potentially unstable or unstable lesions were 95.7% and 79.5%, respectively.