Performance of an automated immunoturbidimetric assay for bovine serum amyloid A.

BACKGROUND: Acute phase proteins are a group of vital constituents of the innate immune system, which may also serve as circulatory biomarkers of inflammation. The major acute phase protein serum amyloid A (SAA) is a reliable and sensitive biomarker in cows, allowing for rapid detection of inflammatory disease. A multispecies automated immunoturbidimetric assay (VET-SAA, Eiken) has been validated for horses, dogs, and cats, and it has been used to measure SAA concentrations in bovine samples. OBJECTIVES: The aim of the present study was to perform an analytical validation of the VET-SAA immunoturbidometric assay based on monoclonal antihuman SAA antibodies for the measurement of SAA in clinical samples from cows. METHODS AND RESULTS: The validation included an assessment of imprecision, inaccuracy, and detection limit, as well as an evaluation of the overlap performance, using banked serum from healthy and sick cows with or without inflammatory disease. Intra- and interassay variation ranged from 0.91% to 2.9% and 2.5% to 5.8%, respectively. The assay was performed with acceptable accuracy within a clinically relevant range of SAA, although minor signs of inaccuracy were detected. Overlap performance was acceptable, with the VET-SAA assay able to differentiate between healthy cows and cows with inflammatory and noninflammatory conditions. The automated VET-SAA assay is considered acceptable for the measurement of SAA in cows.

Acute-phase responses in healthy and diseased rhesus macaques (Macaca mulatta).

Five acute-phase reactants-serum amyloid A (SAA), C-reactive protein (CRP), haptoglobin, albumin, and iron-were measured using commercially available assays in 110 healthy rhesus macaques (Macaca mulatta), and reference intervals were established for future use in health monitoring of this species. Reference intervals established were as follows: SAA, 29.5-87.7 mg/L; CRP, 0-17.5 mg/L; haptoglobin, 354.3-2,414.7 mg/ L; albumin, 36.1-53.0 g/L; and iron, 13.3-40.2 micromol/L. Furthermore, changes in the acute-phase reactants were studied in two additional groups of animals: eight rhesus macaques suffering from acute traumatic injuries and nine rhesus macaques experimentally infected with Mycobacterium tuberculosis reflecting a chronic active inflammation. In animals with inflammation, SAA and haptoglobin concentrations were moderately increased, while CRP increased more than 200-fold. In addition, marked decreases in albumin and iron concentrations were observed. These results show that SAA, CRP, and haptoglobin are positive acute-phase proteins, whereas albumin and iron are negative acute-phase reactants in rhesus macaques.