title: Serum neuron-specific enolase levels from the same patients differ between laboratories: assessment of a prospective post-cardiac arrest cohort.
abstract: BACKGROUND
  In comatose post-cardiac arrest patients, a serum neuron-specific enolase (NSE) level of >33 μg/L within 72 h was identified as a reliable marker for poor outcome in a large Dutch study (PROPAC), and this level was subsequently adopted in an American Academy of Neurology practice parameter. Later studies reported that NSE >33 μg/L is not a reliable predictor of poor prognosis. To test whether different clinical laboratories contribute to this variability, we compared NSE levels from the laboratory used in the PROPAC study (DLM-Nijmegen) with those of our hospital's laboratory (ARUP) using paired blood samples.
  
  
  METHODS
  We prospectively enrolled cardiac arrest patients who remained comatose after resuscitation. During the first 3 days, paired blood samples for serum NSE were drawn at a median of 10 min apart. After standard preparation for each lab, one sample was sent to ARUP laboratories and the other to DLM-Nijmegen.
  
  
  RESULTS
  Fifty-four paired serum samples from 33 patients were included. Although the serum NSE measurements correlated well between laboratories (R = 0.91), the results from ARUP were approximately 30% lower than those from DLM-Nijmegen. Therapeutic hypothermia did not affect this relationship. Two patients had favorable outcomes after hypothermia despite NSE levels measured by DLM-Nijmegen as >33 μg/L.
  
  
  CONCLUSIONS
  Absolute serum NSE levels of comatose cardiac arrest patients differ between laboratories. Any specific absolute cut-off levels proposed to prognosticate poor outcome should not be used without detailed data on how neurologic outcomes correspond to a particular laboratory's method, and even then only in conjunction with other prognostic variables.
authors.affiliation: Stanford Neurocritical Care Program, Stanford Stroke Center, Department of Neurology and Neurological Sciences, Stanford University Medical Center, Stanford, CA, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Mlynash
authors.forename: Marion S
authors.initials: MS
authors.lastname: Buckwalter
authors.forename: Ami
authors.initials: A
authors.lastname: Okada
authors.forename: Anna Finley
authors.initials: AF
authors.lastname: Caulfield
authors.forename: Chitra
authors.initials: C
authors.lastname: Venkatasubramanian
authors.forename: Irina
authors.initials: I
authors.lastname: Eyngorn
authors.forename: Marcel M
authors.initials: MM
authors.lastname: Verbeek
authors.forename: Christine A C
authors.initials: CA
authors.lastname: Wijman
mesh_terms: D015415:Biomarkers / Q000097:blood; D002624:Chemistry, Clinical / Q000592:standards*; D064790:Clinical Laboratory Services / Q000592:standards*; D015331:Cohort Studies; D003128:Coma / Q000378:metabolism* / Q000401:mortality; D006323:Heart Arrest / Q000378:metabolism* / Q000401:mortality; D006801:Humans; D007036:Hypothermia, Induced; D007755:Laboratories, Hospital / Q000592:standards*; D010751:Phosphopyruvate Hydratase / Q000097:blood*; D011379:Prognosis; D011446:Prospective Studies; D015203:Reproducibility of Results; D015996:Survival Rate
chemical_list: D015415:Biomarkers; D010751:Phosphopyruvate Hydratase