title: A new high-sensitive nephelometric method for assaying serum C-reactive protein based on phosphocholine interaction.
abstract: BACKGROUND
  The measurement of C-reactive protein (CRP) concentrations has been of interest as a classical marker of acute phase response; in addition, it has been of particular interest in cardiovascular risk stratification where high-sensitive measurements are necessary. Since CRP is able to bind phospholipids (mainly phosphocholine) in the presence of calcium ions, we explored the possibilities of developing a high-sensitive affordable nephelometric CRP assay based on diluted soy oil emulsions.
  
  
  METHODS
  Serum (or heparinized plasma) was mixed with Intralipid 20% in Tris-calcium buffer (pH 7.5). After 12 min of incubation at 37°C, the CRP-phospholipid complexes were measured by nephelometry (840 nm) using a BN II nephelometer (Siemens). Results (n=97) were compared with those obtained using a typical immunoturbidimetric method (Roche).
  
  
  RESULTS
  Imprecision of the functional nephelometric assay was evaluated using three human serum pools. Within-run coefficients of variation (CVs) for level 1, 2 and 3 were 6.1%, 4.7% and 4.5%, respectively, and between-run CVs were 17.6%, 18.8% and 11.3%, respectively. Good agreement was obtained between the functional nephelometric and the immunoturbidimetric CRP assay in a concentration range from 0.1 mg/L to 50 mg/L (r=0.884). A logit-log calibration curve was made between 0.056 mg/L and 1.785 mg/L. The limit of detection was 0.5 mg/L.
  
  
  CONCLUSIONS
  The functional nephelometric CRP assay allowed high-sensitive CRP determinations in serum and plasma. Since the assay is species independent, the described functional CRP assay could be used for veterinary purposes as well.
authors.forename: Stefanie A
authors.initials: SA
authors.lastname: Drieghe
authors.forename: Hani
authors.initials: H
authors.lastname: Alsaadi
authors.forename: Pierrot L
authors.initials: PL
authors.lastname: Tugirimana
authors.forename: Joris R
authors.initials: JR
authors.lastname: Delanghe
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods*; D002097:C-Reactive Protein / Q000032:analysis* / Q000737:chemistry*; D002138:Calibration; D006801:Humans; D057230:Limit of Detection; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D010767:Phosphorylcholine / Q000737:chemistry*
chemical_list: D010767:Phosphorylcholine; D002097:C-Reactive Protein