Quantification and prospective evaluation of serum NfL and GFAP as blood-derived biomarkers of outcome in acute ischemic stroke patients

Abstract

Identification of reliable and accessible biomarkers to characterize ischemic stroke patients' prognosis remains a clinical challenge. Neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) are markers of brain injury, detectable in blood by high-sensitive technologies. Our aim was to measure serum NfL and GFAP after stroke, and to evaluate their correlation with functional outcome and the scores in rehabilitation scales at 3-month follow-up. Stroke patients were prospectively enrolled in a longitudinal observational study within 24 hours from symptom onset (D1) and monitored after 7 (D7), 30 ± 3 (M1) and 90 ± 5 (M3) days. At each time-point serum NfL and GFAP levels were measured by Single Molecule Array and correlated with National Institute of Health Stroke Scale (NIHSS), modified Rankin scale (mRS), Trunk Control Test (TCT), Functional Ambulation Classification (FAC) and Functional Independence Measure (FIM) scores. Serum NfL and GFAP showed different temporal profiles: NfL increased after stroke with a peak value at D7; GFAP showed an earlier peak at D1. NfL and GFAP concentrations correlated with clinical/rehabilitation outcomes both longitudinally and prospectively. Multivariate analysis revealed that NfL-D7 and GFAP-D1 were independent predictors of 3-month NIHSS, TCT, FAC and FIM scores, with NfL being the biomarker with the best predictive performance.

Keywords: Blood-derived biomarkers; GFAP; NfL; ischemic stroke; predictive factors.

Figure 1.

Trend of sNfL (a) and sGFAP (b) measured in stroke patients (n = 36) at D1, D7, M1, M3 after stroke. The stages of stroke corresponding to the different time-points are reported according to previous literature. The number of patients completing each stage of follow-up is indicated under the x-axis. As reference values, sNfL and sGFAP levels were measured in a group of healthy controls (HC, n = 20). Each box represents the area between the 25th and 75th percentiles [interquartile range, IQR]. Lines inside the boxes represent the median values. White dots represent the mean value for each class. Whiskers extend to the lowest and highest values within 1.5 times the IQR from the box. Statistical analysis was performed by unpaired Mann-Whitney test.

Figure 2.

Correlation plots between sNfL and sGFAP at D1 (a, n = 34), D7 (b, n = 28), M1 (c, n = 26), M3 (d, n = 23) after stroke. Each point represents an individual subject analyzed. Data are shown upon logarithmic transformation of sNfL and sGFAP concentrations.