title: Impact of creatine kinase correction on the predictive value of S-100B after mild traumatic brain injury.
abstract: OBJECTIVE
  To validate a correction factor for the extracranial release of the astroglial protein, S-100B, based on concomitant creatine kinase (CK) levels.
  
  
  METHODS
  The CK- S-100B relationship in non-head injured marathon runners was used to derive a correction factor for the extracranial release of S-100B. This factor was then applied to a separate cohort of 96 mild traumatic brain injury (TBI) patients in whom both CK and S-100B levels were measured. Corrected S-100B was compared to uncorrected S-100B for the prediction of initial head CT, three-month headache and three-month post concussive syndrome (PCS).
  
  
  RESULTS
  Corrected S-100B resulted in a statistically significant improvement in the prediction of 3-month headache (area under curve [AUC] 0.46 vs 0.52, p=0.02), but not PCS or initial head CT. Using a cutoff that maximizes sensitivity (> or = 90%), corrected S-100B improved the prediction of initial head CT scan (negative predictive value from 75% [95% CI, 2.6%, 67.0%] to 96% [95% CI: 83.5%, 99.8%]).
  
  
  CONCLUSIONS
  Although S-100B is overall poorly predictive of outcome, a correction factor using CK is a valid means of accounting for extracranial release. By increasing the proportion of mild TBI patients correctly categorized as low risk for abnormal head CT, CK-corrected S100-B can further reduce the number of unnecessary brain CT scans performed after this injury.
authors.affiliation: Department of Emergency Medicine, University of Rochester School of Medicine, Rochester, NY, USA. jeff_bazarian@urmc.rochester.edu
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Bazarian
authors.forename: Christopher
authors.initials: C
authors.lastname: Beck
authors.forename: Brian
authors.initials: B
authors.lastname: Blyth
authors.forename: Nicolas
authors.initials: N
authors.lastname: von Ahsen
authors.forename: Martin
authors.initials: M
authors.lastname: Hasselblatt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001930:Brain Injuries / Q000097:blood*; D002648:Child; D015331:Cohort Studies; D003402:Creatine Kinase / Q000097:blood*; D005260:Female; D006261:Headache / Q000097:blood; D006801:Humans; D008297:Male; D008875:Middle Aged; D038223:Post-Concussion Syndrome / Q000097:blood; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D009418:S100 Proteins / Q000097:blood*; D012680:Sensitivity and Specificity; D013997:Time Factors; D015599:Trauma Severity Indices
chemical_list: D009418:S100 Proteins; D003402:Creatine Kinase