SPP1 and infection: Furthermore, OPN has been demonstrated to be an independent predictor of both ICU and long-term mortality in critically ill patients (including septic patients); in particular, the prognostic power of OPN levels measured at day three from ICU admission has been found to be superior compared to the one of other routine biomarkers of inflammation, infection and organ failure such as C-reactive protein (CRP), international normalized ratio (INR) and procalcitonin (PCT) [17].