Serum amyloid A in healthy subjects: assessment of reference value using ELISA method

Serum amyloid A (SAA) is a family of acute-phase reactants. The rise of SAA concentration in blood circulation during the acute-phase response is a clinical marker of active inflammation. Despite its practical and analytical advantages, SAA measurement by enzyme-linked immunosorbent assay (ELISA) has been used mainly as a research tool rather than for the routine laboratory testing. This may be partly explained by the lack of robust reference data in the literature for the different commercially available immunoassays. Using the recommended procedures for the production of reference intervals published by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), we developed the SAA reference interval for a well-defined Italian healthy population and investigated the correlation among SAA and C-reactive protein (CRP), the commonly used acute-phase marker. After data normalization, the reference cutoff was calculated as 225 ng/ml. A good correlation between SAA and CRP was found (P < .05). No statistically significant differences was found between males and females when the means of SAA values were compared, suggesting that not gender-partitioned reference range is recommended for this analyte. This study allowed to define a widely accepted reference cutoff for the SAA detected by ELISA, responding to an unmet need of laboratory medicine.