['Few studies demonstrated that serum amyloid A (SAA), a non-specific acute-phase reactant, could be used as a reliable early marker for the diagnosis of late-onset sepsis (LOS).', 'To evaluate the diagnostic value and the dynamics of SAA levels during the course of LOS and to compare it to those of other inflammatory markers.', 'Levels of SAA, C-reactive protein (CRP) and IL-6 together with clinical variables, biochemical parameters and cultures retrieved from all preterm infants suspected of LOS were checked at the first suspicion of sepsis and after 8, 24, 48 and 72 h. Results were compared to healthy, matched infants.', 'One hundred and sixteen infants were included in the study, 38 in the sepsis and 78 in the non-sepsis group. High levels of SAA were observed at sepsis onset, with a gradual decline thereafter, while CRP levels increased only at 24 h after sepsis onset. In the sepsis group, levels of SAA returned faster to baseline than CRP levels. Receiver-operating characteristic analysis values revealed that SAA at 10 mug/ml had the highest sensitivity at 0, 8 and 24 h after sepsis onset (95, 100 and 97%, respectively) and a negative predictive value (97, 100 and 98%, respectively).'] Is serum amyloid A protein a useful inflammatory marker during late-onset sepsis in preterm infants?