title: Comparison of refractometry and biuret assay for measurement of total protein concentration in canine abdominal and pleural fluid specimens.
abstract: OBJECTIVE
  To compare total protein (TP) concentrations in canine pleural and abdominal fluid specimens as measured by refractometry and biuret assay.
  
  
  METHODS
  Diagnostic test evaluation.
  
  
  METHODS
  Data regarding 92 pleural and 148 abdominal fluid specimens from dogs with various diseases.
  
  
  METHODS
  TP concentrations in fluid specimens as measured by refractometry and biuret assay were recorded. Strength of association between sets of measurements was assessed by Spearman rank correlations and Bland-Altman plots. Optimal concentration cutoff for diagnostic discrimination between exudate and nonexudate was identified by construction of receiver operating characteristic curves.
  
  
  RESULTS
  Median TP concentration in pleural fluid specimens was 2.7 g/dL (range, 0.3 to 4.8 g/dL) for refractometry and 2.9 g/dL (range, 0.7 to 5.8 g/dL) for biuret assay. Median TP concentration in abdominal fluid specimens was 3.5 g/dL (range, 0.1 to 6.0 g/dL) for refractometry and 3.5 g/dL (range, 0.6 to 5.7 g/dL) for biuret assay. Correlation was significant between refractometric and biuret results for pleural (ρ = 0.921) and abdominal (ρ = 0.908) fluid. Bland-Altman plots revealed bias of -0.18 g/dL for pleural fluid and -0.03 g/dL for abdominal fluid for refractometry versus biuret assay. With a TP concentration of ≥ 3 g/dL used to distinguish exudate from nonexudate, sensitivity of refractometry was 77% for pleural fluid and 80% for abdominal fluid. Specificity was 100% and 94%, respectively.
  
  
  CONCLUSIONS
  Refractometry yielded acceptable results for measurement of TP concentration in canine pleural and abdominal fluid specimens, providing a more rapid and convenient method than biuret assay.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Rose
authors.forename: Deborah
authors.initials: D
authors.lastname: Funk
authors.forename: Reto
authors.initials: R
authors.lastname: Neiger
mesh_terms: D034841:Abdominal Cavity / Q000502:physiology*; D000818:Animals; D019540:Area Under Curve; D001738:Biuret Reaction / Q000592:standards / Q000662:veterinary*; D004283:Dog Diseases / Q000378:metabolism*; D004285:Dogs; D010996:Pleural Effusion / Q000378:metabolism*; D011506:Proteins / Q000032:analysis*; D012372:ROC Curve; D012031:Refractometry / Q000592:standards / Q000662:veterinary*; D012680:Sensitivity and Specificity
chemical_list: D011506:Proteins