A multi-analyte blood test for acute spinal cord injury

BACKGROUND. Rapid diagnosis to facilitate urgent intervention is critical for treatment of acute spinal cord injury (SCI). We hypothesized that a multi-analyte blood biomarker would support point-of-care SCI diagnosis, correlate with injury severity, and predict long-term neurologic outcomes. METHODS. Droplet digital PCR (ddPCR) assays were designed to amplify differentially hypomethylated genomic loci in spinal cord tissue. An optimized ddPCR assay was applied to cell-free DNA (cfDNA) from plasma samples collected from prospectively enrolled acute SCI patients. Targeted proteomic profiling was also performed. Spinal cord-derived cfDNA and plasma proteins were tested for their association with SCI and ability to predict conversion in American Spinal Injury Association (ASIA) score at 6 months. RESULTS. A bespoke ddPCR assay detected spinal cord-derived cfDNA in plasma of 50 patients with acute SCI (AUC: 0.89, 95% CI 0.83-0.95, P < 0.0001). Levels of cfDNA were highest in patients with the most severe injury, i.e., ASIA A, compared with those with ASIA B (P = 0.04), ASIA C (P = 0.009), and ASIA D injuries (P < 0.001). Dimensionality reduction identified 4 candidate proteins (FABP3, REST, IL-6, NF-H) that were integrated with spinal cord-derived cfDNA to derive the Spinal Cord Injury Index (SCII), which has high sensitivity and specificity for SCI diagnosis (AUC: 0.91, 95% CI 0.82-0.99, P < 0.0001), correlates with injury severity (P < 0.0001), and predicts 6-month neurologic improvement (AUC: 0.77, 95% CI 0.61-0.93, P = 0.006). CONCLUSION. The detection of spinal cord-derived cfDNA and plasma protein alterations as part of a multi-analyte blood test can inform SCI diagnosis and prognosis.