2022 A Multi-Analyte Blood Test for Acute Spinal Cord Injury

INTRODUCTION: Physical examination and neuroimaging are essential components of acute spinal cord injury (SCI) management, yet they have limited spatiotemporal resolution and do not capture molecular features of SCI. Recent advances in methylation profiling of cell-free DNA (cfDNA) allow for detection of cell death in a tissue specific fashion, raising the possibility of developing spinal cord-specific biomarkers. METHODS: We performed methylome profiling of human spinal cord tissue (N=6 subjects via rapid autopsy program) and integrated these profiles with methylomes from 25 tissue/cell types, including cortical neurons, deriving a signature of spinal cord identity. We designed a bespoke droplet digital PCR (ddPCR) assay to target promising CpG sites, applied this ddPCR assay to cfDNA extracted from preoperative blood samples, and performed targeted proteomics in the same samples. Finally, we developed an algorithm to integrate cfDNA and protein into a unified Spinal Cord Injury Index (SCII). RESULTS: The ddPCR assay was applied to cfDNA derived from the plasma of 50 prospectively enrolled patients with acute SCI (AUC: 0.89, 95% CI 0.83-0.95, P<0.0001) detecting spinal cord-specific cfDNA at levels down to 4.4 haploid genome equivalents/mL plasma. A dimensionality-reduction algorithm selected a parsimonious set of four proteins associated with long-term neurologic improvement, which were with integrated spinal cord-specific cfDNA to derive the SCII. The SCII discriminated SCI patients from controls, correlated with injury, and predicted six-month ASIA conversion. CONCLUSIONS: A multi-analyte assay detects neuroglial cell death in the blood of SCI patients and predicts clinically meaningful endpoints. Future work will focus on prospective validation with serial blood draws and translation to other acute neurosurgical pathology.