title: The agreement between abnormal venous lactate and arterial lactate in the ED: a retrospective chart review.
abstract: BACKGROUND
  The evidence for prognostication using lactate is often based on arterial lactate (AL). Arterial sampling is painful and difficult, and carries risks. Studies comparing peripheral venous lactate (PVL) with AL showed little difference but predominantly included patients with normal lactate. The objective of this study was to measure agreement between PVL and AL in patients with elevated venous lactate.
  
  
  METHODS
  This is a retrospective cross-sectional study.
  
  
  METHODS
  ED patients age≥16, attending from October 2010 to June 2011 inclusive, with PVL≥2.0 mmol/L and AL taken within 1 hour.
  
  
  METHODS
  intravenous fluid prior to or between initial venous and arterial sampling. Primary endpoint: agreement between PVL and AL defined as mean difference±95% limits of agreement (LOA). The misclassification rate was assessed.
  
  
  RESULTS
  N=232. VL median 3.50 mmol/L, range 2.00 to 15.00 mmol/L. AL median 2.45 mmol/L, range 1.0 to 13.2 mmol/L. The mean difference±SD between PVL and AL for all patients was 1.06±1.30 mmol/L (95%LOA -1.53 to 3.66 mmol/L). Using a cut-off of 2 mmol/L and 4 mmol/L, 36.2% and 17.9% of patients respectively were incorrectly classified as having elevated lactate.
  
  
  CONCLUSIONS
  We report greater bias between VL and AL with broader LOA than previously documented. This may partly be due to the fact that we studied only patients with abnormal venous values, for whom close agreement would confer greatest clinical significance. The agreement between abnormal PVL and AL is poor and the high rate of misclassification may suggest that PVL is not a good substitute for AL if the venous lactate is abnormal.
authors.affiliation: Emergency Department, Royal London Hospital, Whitechapel, London, E1 1BB, UK. Electronic address: ben.bloom@nhs.net.
authors.forename: B
authors.initials: B
authors.lastname: Bloom
authors.affiliation: Emergency Department, Royal London Hospital, Whitechapel, London, E1 1BB, UK.
authors.forename: J
authors.initials: J
authors.lastname: Pott
authors.affiliation: Emergency Department, Hôpital Pitié-Salpêtrière, 47-83 Boulevard de l'Hôpital, 75013 Paris, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Freund
authors.affiliation: Emergency Department, Royal London Hospital, Whitechapel, London, E1 1BB, UK.
authors.forename: J
authors.initials: J
authors.lastname: Grundlingh
authors.affiliation: Emergency Department, Royal London Hospital, Whitechapel, London, E1 1BB, UK.
authors.forename: T
authors.initials: T
authors.lastname: Harris
mesh_terms: D001158:Arteries / Q000737:chemistry; D001800:Blood Specimen Collection / Q000379:methods; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007773:Lactates / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014680:Veins / Q000737:chemistry
chemical_list: D007773:Lactates