title: Adjusting for bias in C-reactive protein levels when using a vitros slide method in infants.
abstract: OBJECTIVE
  Low total serum protein levels may cause a positive bias on C-reactive protein (CRP) detected by the Vitros 250 Chemistry System (Ortho-Clinical Diagnostics, Inc., Johnson & Johnson Co., Raritan, NJ). Low total serum protein levels are observed in some infants. Our objective was to define a cutoff value for normal levels of CRP measured on the Vitros System that is comparable to the cutoff value of 1.0 mg/dL measured by rate nephelometry on a Beckman Array System (Beckman Instruments Inc., Fullerton, CA).
  
  
  METHODS
  CRP was prospectively measured on the same serum sample on Vitros and Beckman systems. Using a result of ≥1.0 as the "gold standard" definition of an abnormal CRP, measures of association were calculated.
  
  
  RESULTS
  CRP was measured in 981 blood samples that were collected from 361 infants. A cutoff CRP level using the Vitros system at 1.5 mg/dL had the highest sensitivity and negative predictive value comparable to 1.0 mg/dL measured by nephelometry. By regression analysis, each increase by 1 mg/dL by nephelometry caused an increase by 1.5 mg/dL on the Vitros system (R(2) = 0.94; p < 0.001; slope = 0.66; 95% confidence intervals, 0.65, 0.67).
  
  
  CONCLUSIONS
  In infants, when measuring CRP levels by Vitros CRP slide system, a normal reference level of 1.5 mg/dL instead of 1 mg/dL should be used.
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Tennessee Health Science Center (UTHSC), Memphis, Tennessee.
authors.forename: Mohamad T
authors.initials: MT
authors.lastname: Elabiad
authors.affiliation: Division of Biostatistics and Pediatrics, Department of Epidemiology and Public Health, Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Kristopher L
authors.initials: KL
authors.lastname: Arheart
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Tennessee Health Science Center (UTHSC), Memphis, Tennessee.
authors.forename: Sheldon B
authors.initials: SB
authors.lastname: Korones
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Tennessee Health Science Center (UTHSC), Memphis, Tennessee.
authors.forename: Massroor
authors.initials: M
authors.lastname: Pourcyrous
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods*; D002097:C-Reactive Protein / Q000032:analysis*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D009391:Nephelometry and Turbidimetry; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012016:Reference Values
chemical_list: D002097:C-Reactive Protein