title: Evaluation of an alternative S100b assay for use in cardiac surgery: relationship with microemboli and neuropsychological outcome.
abstract: BACKGROUND
  The aim of the study was to investigate the relationship between S100b release, neuropsychological outcome and cerebral microemboli. Peri-operative assay of the astroglial cell protein S100b has been used as a marker of cerebral damage after cardiac surgery but potential assay cross-reactivity has limited its specificity. The present study uses an alternative enzyme-linked immunoabsorbant assay (ELISA) for serum S100b that has documented sensitivity and specificity data in patients undergoing coronary artery bypass grafting (CABG).
  
  
  METHODS
  Fifty-five consecutive patients undergoing routine CABG surgery received serial venous S100b sampling at five time points: i) Pre-operative, ii) At the end of cardiopulmonary bypass (CPB), iii) 6 hrs, iv) 24 hrs and v) 48 hrs post skin closure. A previously described sandwich ELISA with monoclonal anti- S100b was used. This assay has a lower limit of detection of 0.04 microg/L and < 0.006% reactivity with S100a at a concentration of 100 microg/L S100a. Cerebral microemboli during surgery were recorded by transcranial Doppler monitor over the right middle cerebral artery. Evidence of cerebral impairment was obtained by comparing patients' performance in a neuropsychological battery of 9 tests administered 6-8 weeks post-operatively with their pre-operative scores.
  
  
  RESULTS
  There was a significant increase in S100b only at the end of bypass (mean 0.30 microg/L, SD +/- 0.33 and range .00 to 1.57). S100b levels at the end of bypass did not correlate with neuropsychological outcome or microemboli counts.
  
  
  CONCLUSIONS
  The low levels of S100b detected using the present assay, despite its high sensitivity and despite the routine use of cardiotomy suction, suggest that the assay may have higher specificity for cerebral S100b than previously used assays. There was no evidence that this assay is related to neuropsychological change or cerebral microemboli in cardiac surgery.
authors.affiliation: Centre for Behavioural and Social Sciences in Medicine, University College London, UK.
authors.forename: D C
authors.initials: DC
authors.lastname: Whitaker
authors.forename: A J E
authors.initials: AJ
authors.lastname: Green
authors.forename: J
authors.initials: J
authors.lastname: Stygall
authors.forename: M J G
authors.initials: MJ
authors.lastname: Harrison
authors.forename: S P
authors.initials: SP
authors.lastname: Newman
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D001930:Brain Injuries / Q000150:complications* / Q000601:surgery; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006331:Heart Diseases / Q000097:blood / Q000601:surgery*; D006801:Humans; D020766:Intracranial Embolism / Q000175:diagnosis*; D007431:Intraoperative Complications / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D009414:Nerve Growth Factors / Q000097:blood*; D009483:Neuropsychological Tests; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000097:blood*
chemical_list: D015415:Biomarkers; D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579160:S100B protein, human