title: Serum S100B levels after meningioma surgery: A comparison of two laboratory assays.
abstract: BACKGROUND
  S100B protein is a potential biomarker of central nervous system insult. This study quantitatively compared two methods for assessing serum concentration of S100B.
  
  
  METHODS
  A prospective, observational study performed in a single tertiary medical center. Included were fifty two consecutive adult patients undergoing surgery for meningioma that provided blood samples for determination of S100B concentrations. Eighty samples (40 pre-operative and 40 postoperative) were randomly selected for batch testing. Each sample was divided into two aliquots. These were analyzed by ELISA (Sangtec) and a commercial kit (Roche Elecsys(R)) for S100B concentrations. Statistical analysis included regression modelling and Bland-Altman analysis.
  
  
  RESULTS
  A parsimonious linear model best described the prediction of commercial kit values by those determined by ELISA (y = 0.045 + 0.277*x, x = ELISA value, R2 = 0.732). ELISA measurements tended to be higher than commercial kit measurements. This discrepancy increased linearly with increasing S100B concentrations. At concentrations above 0.7 microg/L the paired measurements were consistently outside the limits of agreement in the Bland-Altman display. Similar to other studies that used alternative measurement methods, sex and age related differences in serum S100B levels were not detected using the Elecsys(R) (p = 0.643 and 0.728 respectively).
  
  
  CONCLUSIONS
  Although a generally linear relationship exists between serum S100B concentrations measured by ELISA and a commercially available kit, ELISA values tended to be higher than commercial kit measurements particularly at concentrations over 0.7 microg/L, which are suggestive of brain injury. International standardization of commercial kits is required before the predictive validity of S100B for brain damage can be effectively assessed in clinical practice.
authors.affiliation: The Intensive Care Unit of the Shaare Zedek Medical Center, affiliated with the Hebrew University, POB 3235, Jerusalem 91031, Israel.
authors.forename: Sharon
authors.initials: S
authors.lastname: Einav
authors.affiliation: The Department of Neurosurgery, Hadassah Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Eyal
authors.initials: E
authors.lastname: Itshayek
authors.affiliation: The Epidemiology Unit, Hadassah Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Kark
authors.affiliation: The Department of Neurology, Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Haim
authors.initials: H
authors.lastname: Ovadia
authors.affiliation: The Department of Anesthesia, Hadassah Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Carolyn F
authors.initials: CF
authors.lastname: Weiniger
authors.affiliation: The Department of Neurosurgery, Hadassah Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Yigal
authors.initials: Y
authors.lastname: Shoshan