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

Background: This 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. Methods: The 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. Results: The GFAP assay covered a concentration range up to 18 mu g/L with an analytical sensitivity of 0.014 mu g/L. The intra-assay precision was 3.5% at 1.55 mu g/L (n =20) and 4.1% at 0.39 mu g/L (n =20). The inter-assay precision was 3.8% at 9.1 mu g/L (n = 10) and 10.3 % at 0.21 mu g/L (n = 9). Normal controls (n = 46) showed non-detectable GFAP with a 99% upper limit of < 0.04 mu g/L. GFAP values were associated with progression and severity of the illness in acute stroke patients. Conclusions: We 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. (c) 2005 Elsevier B.V. All rights reserved.