title: Comparison of two analyzers for measurement of plasma total carbon dioxide concentration in horses.
abstract: OBJECTIVE
  To determine the degree of agreement between 2 analyzers for measurement of total CO₂ concentration (ctCO₂) in equine plasma.
  
  
  METHODS
  6 healthy untrained horses, 6 trained Standardbreds undergoing a simulated race protocol, and 135 trained Standardbreds at a racetrack.
  
  
  METHODS
  Jugular venous blood samples were obtained from all horses. Two analyzers (commonly used analyzer A and less expensive analyzer B) were used to measure plasma ctCO₂ in each sample. Validation of both analyzers was conducted in accordance with guidelines established by the Clinical and Laboratory Standards Institute and involved characterization of linearity, total analytic error, and bias estimation.
  
  
  RESULTS
  Total analytic error (instrument SD) was 0.58 mmol/L (coefficient of variation, 1.6%) and 0.49 mmol/L (coefficient of variation, 1.4%) for analyzers A and B, respectively, when measuring an aqueous standard containing 36.0 mmol of CO₂/L. A 1 g/L decrease in plasma protein concentration corresponded to an increase in ctCO₂ measured with analyzer B of 0.065 mmol/L. A difference plot indicated that analyzer B produced values 2.7% higher than analyzer A for 103 samples from the 6 trained and exercised Standardbreds (mean plasma protein concentration, 67 g/L).
  
  
  CONCLUSIONS
  Analyzer B provided adequate precision and linearity for measurement of ctCO₂ from 5 to 40 mmol/L and was therefore suitable for measuring ctCO₂ in equine plasma, provided allowances are made for changes in plasma protein concentration.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, USA. constabl@purdue.edu
authors.forename: Peter D
authors.initials: PD
authors.lastname: Constable
authors.forename: Stacy H
authors.initials: SH
authors.lastname: Tinkler
authors.forename: Laurent L
authors.initials: LL
authors.lastname: Couëtil
mesh_terms: D000818:Animals; D001774:Blood Chemical Analysis / Q000295:instrumentation / Q000662:veterinary*; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006736:Horses / Q000097:blood* / Q000502:physiology; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D002245:Carbon Dioxide