title: Analytical evaluation of particle-enhanced immunonephelometric assays for C-reactive protein, serum amyloid A and mannose-binding protein in human serum.
abstract: Against a background of growing interest in more sensitive assays for quantifying various acute phase proteins, we evaluated the performance of recently developed tests for C-reactive protein (CRP), serum amyloid A (SAA) and mannose-binding protein (MBP) on the Behring nephelometer II (BNII). Sample results outside the calibration ranges of 3.5 to 220 mg/L for CRP, 3.3 to 215 mg/L for SAA and 0.09 to 5.6 mg/L for MBP were automatically re-measured at another dilution. The lower limits of detection were 0.01, 0.7 and 0.01 mg/L for CRP, SAA and MBP, respectively. The coefficients of variation (CV) for intra- (n > or = 20) and inter- (n > or = 15) assay precision were < 5.2% and < 8.5%, respectively, for the three proteins at concentrations representing low, normal and high. Linearity for each method was within 5% of the expected values throughout the calibration range. We observed no significant interference from bilirubin (up to 300 mg/L) or haemoglobin (up to 10 g/ L) for the three tests. Method comparison studies performed for CRP and SAA yielded the following results: y (CRP on BNII) = 0.75x (ELISA, Hemagen) -0.25 mg/L (r = 0.981, Sy/x = 2.1 mg/L; y (SAA on BNII) = 1.44x (ELISA, Hemagen) -9.9 mg/L (r = 0.972, Sy/x = 6.9 mg/L), where ELISA is enzyme-linked immunosorbent assay. Reference intervals established in 261 adult blood donors (aged 36.2 +/- 9.0 years) were found to be log-normal with 2.5th, 50th, and 97.5th centiles of < 0.17, 1.00 and 10.1 mg/L for CRP, < 0.84, 2.10 and 9.70 mg/L for SAA; and 0.30, 1.28 and 4.10 mg/L for MBP. We observed no relationship with CRP concentration and age; however, SAA levels increased with age while MBP levels decreased. The BNII provides a simple, rapid and sensitive system for measuring CRP, SAA and MBP in human serum.
authors.affiliation: Foundation for Blood Research, Scarborough, Maine 04070-0190, USA. tledue@fbr.org
authors.forename: T B
authors.initials: TB
authors.lastname: Ledue
authors.forename: D L
authors.initials: DL
authors.lastname: Weiner
authors.forename: J D
authors.initials: JD
authors.lastname: Sipe
authors.forename: S E
authors.initials: SE
authors.lastname: Poulin
authors.forename: M F
authors.initials: MF
authors.lastname: Collins
authors.forename: N
authors.initials: N
authors.lastname: Rifai
mesh_terms: D000328:Adult; D001053:Apolipoproteins / Q000032:analysis*; D002097:C-Reactive Protein / Q000032:analysis*; D002352:Carrier Proteins / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay; D005069:Evaluation Studies as Topic; D006801:Humans; D007106:Immune Sera; D037241:Mannose-Binding Lectins; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000685:Serum Amyloid A Protein / Q000032:analysis*
chemical_list: D001053:Apolipoproteins; D002352:Carrier Proteins; D007106:Immune Sera; D037241:Mannose-Binding Lectins; D000685:Serum Amyloid A Protein; D002097:C-Reactive Protein