Mar 10, 1994 - value and the RID result for each sample were analyzed by linear ..... Whitehead AS, de Beer MC, Steel DM, Rite M, Lelias JM, Lane. WS, et al ...
CLIN.CHEM.40/7, 1284-1290
(1994)
Enzymes and Protein
#{149}
Markers
Rapid Automated Enzyme Immunoassay of Serum Amyloid A Julie Wilkins,’ J. Ruth Gallimore,2 Glenys A. Tennent,2 Rijswijk,3 Edwin G. Moore,’ and Mark B. Pepys2’4
Serum amyloid A (SAA), a sensitive acute-phase protein, is the precursor of AA fibrils in reactive amyloidosis. However, SAA is poorly immunogenic, and development and standardization of immunoassays of this protein have been difficult. We established an automated polyclonal/ monoclonal microparticlecapture enzyme immunoassay, standardized with the World Health Organization prospective reference standard for SAA. A stabilized concentrate of SAA was used for controls and calibrators. The assay range was 1-750 mg/L with CVs 1000 mg/L within 24-48 h of an ‘Abbott Diagnostics Division, AbbOtt Laboratories, North Chicage, IL 60064. 2lmmunological Medicine Unit, Royal Postgraduate Medical School, Hammersmith Hospital, Du Cane Rd., London W12 ONN, UK 3Division of Rheumatology, State University Hospital, Groningen, The Netherlands. 4Address correspondence to this author. Fax +44-81-749-7478. 5Nonstandard abbreviations: SAA, serum amyloid A protein; WHO, World Health Organization; HDL, high-density lipoprotein; apoAl, apolipoprotein Al; CRP, C-reactive protein; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; MEIA, microparticle capture enzyme immunoassay; and RID, radial immunodiffusion. Received January 10, 1994; accepted March 10, 1994. 1284
CLINICAL
CHEMISTRY,
Vol. 40, No. 7, 1994
Philip N. Hawkins,2
Pieter C. Limburg,3
Martin
H. van
acute stimulus; with ongoing chronic inflammation the concentration may remain high (2,3). Certain isoforms of SAA, the products of different genes, are predominantly synthesized by macrophages, adipocytes,and other cells. Although these isoforms also associate with HDL, their acute-phase synthesis is stimulated differently and presumably they have different functions (4). There is also a closely relatedfamily of trace apoproteins of HDL that are not acute-phase reactants(5). In most circumstances the serum concentration of SAA correlates with that of the classical and highly sensitive acute-phase reactant, C-reactive protein (CRP) (3), but SAA reaches higher concentrations and may respond more rapidly. The cytokine regulation of SAA production is also different from that of CRP, and the differential acute-phase responses of SAA and CRP to different stimuli may be clinically important (6-10).
Most of the routinely
available
commercial
assays for
CRP detect only amounts >5 mgfL, whereas 50% of healthy subjects have CRP concentrations in the range of 0.07-0.8 mgfL, and 90% have
