Glial fibrillary acidic protein is highly correlated with brain injury.
BACKGROUND
Glial fibrillary acidic protein (GFAP) is an intermediate filament protein found in the cytoskeleton of astroglia. Recent work has indicated that GFAP may serve as a serum marker of traumatic brain injury (TBI) that is released after central nervous system cell damage.


METHODS
Serum from 51 critically injured trauma patients was prospectively collected on admission and on hospital day 2. All patients underwent an admission head computed tomography (CT) scan as a part of their clinical evaluation. Patients with facial fractures in the absence of documented TBI and patients with spinal cord injury were excluded. Demographic and outcome data were collected prospectively. Serum GFAP was measured in duplicate using enzyme-linked immunosorbent assay techniques.


RESULTS
Thirty-nine (76%) of the 51 patients had CT-documented TBI. The study cohort was 72.5% men with a mean age of 43 years and mean Injury Severity Score (ISS) of 30.2. There were no statistically significant demographic differences between the two groups. At admission day, the mean GFAP level in non-TBI patients was 0.07 pg/mL compared with 6.77 pg/mL in TBI patients (p = 0.002). On day 2 the mean GFAP level was 0.02 in non-TBI patients compared with 2.17 in TBI patients (p = 0.003). Using regression analysis to control for age, sex, and ISS, the Head Abbreviated Injury Scale was predictive of the level of GFAP on both days 1 and 2 (p values 0.006 and 0.026, respectively). Although GFAP levels were not predictive of increased hospital length of stay, intensive care unit length of stay, or ventilator days, high GFAP levels on hospital day 2 were predictive of mortality when controlling for age, sex, and ISS (odds ratio 1.45, p value 0.028). The area under the receiver operating characteristic curve for GFAP was 0.90 for day 1 and 0.88 for day 2. A GFAP cutoff point of 1 pg/mL yielded 100% specificity and 50% to 60% sensitivity for TBI.


CONCLUSIONS
GFAP is a serum marker of TBI, and persistent elevation on day 2 is predictive of increased mortality. Excellent specificity for CT-documented brain injury was found using a cutoff point of 1 pg/mL.
Division of Clinical and Outcomes Research, R. Adams Cowley Shock Trauma Center, Baltimore, Maryland 21201, USA.
Kimberly M
KM
Lumpkins
Grant V
GV
Bochicchio
Kaspar
K
Keledjian
J Marc
JM
Simard
Maureen
M
McCunn
Thomas
T
Scalea
D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000097:blood; D001930:Brain Injuries / Q000097:blood* / Q000000981:diagnostic imaging / Q000401:mortality*; D016022:Case-Control Studies; D002423:Cause of Death; D005260:Female; D015600:Glasgow Coma Scale; D005904:Glial Fibrillary Acidic Protein / Q000097:blood*; D006801:Humans; D015601:Injury Severity Score; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011336:Probability; D011446:Prospective Studies; D012372:ROC Curve; D012016:Reference Values; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D016019:Survival Analysis; D014057:Tomography, X-Ray Computed
D015415:Biomarkers; D005904:Glial Fibrillary Acidic Protein