What is measured: SAA1.1, SAA1.1dr, SAA1.1drs, SAA1.2, SAA1.2dr, SAAdrs, SAA1.3, SAA1.3drs, SAA2.1, SAA2.1dr, SAA, 2.1drs, SAA2.2, SAA2.2dr, and SAA2.2drs. SAAt is the total concentration of detected serum amyloid A isoforms.
Method(s): MALDI-TOF MS (1).
Serum amyloid A (SAA) is an acute-phase reactant of about 12kDa mass, which can increase more than 1,000-fold during acute inflammation and infections. SAA is an apolipoprotein and involved in cholesterol transport. During inflammation SAA displaces apoA-I in HDL. In humans, acute phase SAA is expressed by two genes, SAA1 and SAA2, which give rise to 5 different isoforms. In addition, N-terminally truncated SAA-isoforms have been recently described, which may have clinical implications since the N-terminus of SAA is critical for amyloid fibrils formation. Furthermore, the truncated variants have lower clearance than native SAA. Chronically elevated levels of SAA has been related to secondary amyloidosis, rheumatoid arthritis or multiple sclerosis. SAA has become a potential biomarker for several chronic diseases, such as diabetes, cardiovascular disease and different types of cancers.
Assessment of inflammation.
Matrix: EDTA plasma and serum.
Volume: Minimum volume is 30 µL, but 100 µL is optimal and allows reanalysis.
Preparation: The blood sample must be centrifuged and the plasma/serum fraction put on ice, and frozen.
Serum Amyloid A is stable for 2 month at -20 °C. Long-term storage requires -80 °C.
Reported values: 0-20 µg/ml.
Intraclass correlation coefficient (ICC): 0.4-0.7.
1. Gao, J., Meyer, K., Borucki, K., and Ueland, P.M. (2018). Multiplex immuno-MALDI-TOF MS for targeted quantification of protein biomarkers and their proteoforms related to inflammation and renal dysfunction. Anal Chem 90, 3366-373.