Spine Instability Neoplastic Score: agreement across different medical and surgical specialties

Abstract

Background context: Spinal instability is an acknowledged complication of spinal metastases; in spite of recent suggested criteria, it is not clearly defined in the literature.

Purpose: This study aimed to assess intra and interobserver agreement when using the Spine Instability Neoplastic Score (SINS) by all physicians involved in its management.

Study design: Independent multicenter reliability study for the recently created SINS, undertaken with a panel of medical oncologists, neurosurgeons, radiologists, orthopedic surgeons, and radiation oncologists, was carried out.

Patient sample: Ninety patients with biopsy-proven spinal metastases and magnetic resonance imaging, reviewed at the multidisciplinary tumor board of our institution, were included.

Outcome measures: Intraclass correlation coefficient (ICC) was used for SINS score agreement. Fleiss kappa statistic was used to assess agreement on the location of the most affected vertebral level; agreement on the SINS category ("stable," "potentially stable," or "unstable"); and overall agreement with the classification established by tumor board.

Methods: Clinical data and imaging were provided to 83 specialists in 44 hospitals across 14 Spanish regions. No assessment criteria were pre-established. Each clinician assessed the SINS score twice, with a minimum 6-week interval. Clinicians were blinded to assessments made by other specialists and to their own previous assessment. Subgroup analyses were performed by clinicians' specialty, experience (≤7, 8-13, ≥14 years), and hospital category (four levels according to size and complexity). This study was supported by Kovacs Foundation.

Results: Intra and interobserver agreement on the location of the most affected levels was "almost perfect" (κ>0.94). Intra-observer agreement on the SINS score was "excellent" (ICC=0.77), whereas interobserver agreement was "moderate" (ICC=0.55). Intra-observer agreement in SINS category was "substantial" (k=0.61), whereas interobserver agreement was "moderate" (k=0.42). Overall agreement with the tumor board classification was "substantial" (κ=0.61). Results were similar across specialties, years of experience, and hospital category.

Conclusions: Agreement on the assessment of metastatic spine instability is moderate. The SINS can help improve communication among clinicians in oncology care.

Keywords: Medical specialty; Observer agreement; Reliability analysis; Spinal instability; Spinal metastases; Spine Instability Neoplastic Score.