The long pentraxin-3 (PTX3) is a key component of the humoral arm of the innate 
immune system. PTX3 is produced locally in response to pro-inflammatory stimuli. 
To investigate PTX3 levels and its use as a biomarker in patients with systemic 
inflammation, we developed a solid-phase enzyme-linked immunosorbent assay based 
on novel anti-PTX3 monoclonal antibodies detecting PTX3 with high sensitivity. 
The assay was applied on 261 consecutive patients admitted to an intensive care 
unit prospectively monitored with the systemic inflammatory response syndrome 
(SIRS). 100 blood donors were included as controls. PTX3 levels were elevated in 
patients (median = 71.3 ng/ml) compared with the controls (median = 0 ng/ml) 
(Mann-Whitney, p<0.0001). ROC analysis showed that PTX3 levels were 
significantly specific (85.0%) and sensitive (89.1%) to discriminate between 
healthy controls and patients (area under the curve (AUC) 0.922 (95% CI 0.892 to 
0.946, p<0.0001)). Higher levels of PTX3 were associated with the development of 
sepsis, severe sepsis and septic shock (p = 0.0001). The serum levels of PTX3 
correlated significantly with SAPS2 score (Spearman's rho 0.28, p<0.0001). 
Patients with high levels of PTX3 at admission did have a higher 90 day 
mortality rate than patients with the 25% lowest levels (Cox regression 
analysis, hazard ratio 3.0, p = 0.0009). In conclusion, we have established a 
highly sensitive and robust assay for measurement of PTX3 and found that its 
serum concentrations correlated with disease severity and mortality in patients 
with SIRS and sepsis.