Rapid immunoassay for the determination of glial fibrillary acidic protein (GFAP) in serum

BackgroundThis study was aimed to develop a sensitive and rapid assay for the determination of glial fibrillary acidic protein (GFAP) in serum and to evaluate the clinical applicability in serum samples from patients with acute stroke.MethodsThe two-site chemiluminometric immunoassay, intended to use in a near-patient setting with a single incubation step (20 min), was used to measure serum samples from healthy blood donors and from patients with brain injury and correlated to serum S100B levels.ResultsThe GFAP assay covered a concentration range up to 18 μg/L with an analytical sensitivity of 0.014 μg/L. The intra-assay precision was 3.5% at 1.55 μg/L (n = 20) and 4.1% at 0.39 μg/L (n = 20). The inter-assay precision was 3.8% at 9.1 μg/L (n = 10) and 10.3 % at 0.21 μg/L (n = 9). Normal controls (n = 46) showed non-detectable GFAP with a 99% upper limit of < 0.04 μg/L. GFAP values were associated with progression and severity of the illness in acute stroke patients.ConclusionsWe have developed an improved assay for the measurement of GFAP levels in serum. Serum GFAP is a potential marker for prognosis and outcome in patients with central nervous system disorders.