Neurofilament medium polypeptide (NFM) protein concentration is increased in CSF and serum samples from patients with brain injury

Background: Brain injury is a medical emergency that needs to be diagnosed and treated promptly. Several proteins have been studied as biomarkers of this medical condition. The aims of this study were to: 1) evaluate the selectivity and precision of a commercial ELISA kit for neurofilament medium polypeptide (NFM) protein; and 2) evaluate the concentration in cerebrospinal fluid (CSF) and serum of healthy individuals and patients with brain damage. Methods: An ELISA from Elabscience was used. The selectivity was evaluated using size-exclusion chromatography and mass spectrometry. Intra- and inter-batch coefficients of variation (CV) were also studied. Fifty-one CSF samples from 36 age-matched patients with hemorrhagic stroke (HS) (n = 30), ischemic stroke (IS) (n = 11) and healthy individuals (n = 10) were assayed. In addition, serum samples from healthy volunteers (n = 47), 68 serum samples from seven patients with HS, 106 serum samples from 12 patients with traumatic brain injury (TBI) and 68 serum samples from 68 patients with mild traumatic brain injury (mTBI) were also analyzed. Results: NFM was identified in the chromatographic fraction with highest immunoreactivity. The intra- and inter-batch CVs were ≤ 10% and ≤ 13%, respectively. The CSF-NFM concentration in HS was significantly higher (p < 0.0001) than in IS and controls. Serum NFM concentration ranged from 0.26 to 8.57 ng/mL in healthy individuals (median = 2.29), from 0.97 to 42.4 ng/mL in HS (median = 10.8) and from 3.48 to 45.4 ng/mL in TBI (median = 14.7). Finally, 44% of patients with mTBI had increased NFM concentration, with significantly higher levels (p = 0.01) in patients with polytrauma. Conclusions: To our knowledge this is the first study describing increased NFM levels in CSF and serum from patients with brain damage.