Analytical evaluation of particle-enhanced immunonephelometric assays for C-reactive protein, serum amyloid A and mannose-binding protein in human serum

Ann Clin Biochem. 1998 Nov;35 ( Pt 6):745-53. doi: 10.1177/000456329803500607.

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.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Apolipoproteins / analysis*
  • C-Reactive Protein / analysis*
  • Carrier Proteins / blood*
  • Enzyme-Linked Immunosorbent Assay
  • Evaluation Studies as Topic
  • Humans
  • Immune Sera
  • Mannose-Binding Lectins
  • Nephelometry and Turbidimetry / methods*
  • Reference Standards
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Serum Amyloid A Protein / analysis*

Substances

  • Apolipoproteins
  • Carrier Proteins
  • Immune Sera
  • Mannose-Binding Lectins
  • Serum Amyloid A Protein
  • C-Reactive Protein