An In Vitro Diagnostic for Multiple Sclerosis Based on C-peptide Binding to Erythrocytes

OBJECTIVE: To investigate the utility of a blood-based lab test as an aid in identifying patients with Multiple Sclerosis (MS). METHODS: Whole blood from subjects with MS, non-MS neurologic diseases, and healthy controls was centrifuged to isolate erythrocytes. Following the addition of exogenous C-peptide, the supernatant was assayed for remaining C-peptide using an enzyme linked immunosorbent assay (ELISA). RESULTS: The cohort included subjects with MS (n = 86), other non-MS neurologic diseases (OND n = 75), and healthy controls (n = 39). The average C-peptide bound to erythrocytes in MS samples (3.51 ± 0.59 pmol) was significantly higher than non-MS subjects (2.23 ± 0.51 pmol; p < 0.001) and healthy controls (1.99 ± 0.32 pmol; p < 0.001). Using a cutoff of 3.04 pmol of C-peptide uptake, the test exhibited a sensitivity of 98.3% and specificity of 89.5%. A receiver-operator characteristic (ROC) curve generated from the ratio of the sensitivity to 1-selectivity resulted in an area under the curve of 0.97. CONCLUSIONS: Exogenous C-peptide binding to erythrocytes has potential value in distinguishing MS subjects from non-MS neurologic diseases and healthy controls.