The purpose of the study is to evaluate the real-time performance of a new host response test (SeptiCyte RAPID) for differentiating sepsis from non-infection/systemic inflammatory response syndrome among patients suspected of sepsis within the first 24 hours of intensive care unit (ICU) admission.

The ability of SeptiCyte RAPID to differentiate sepsis from infection-negative systemic inflammation will be determined using retrospective physician diagnosis performed by an external panel of three physicians not involved with the care of the patients.

Inclusion Criteria:

1. ≥18 years old on the date of ICU admission

2. Systemic Inflammatory Response Syndrome (SIRS) present, as defined by the presence of two or more of the following:

   1. Temperature > 38°C or < 36°C
   2. Heart Rate > 90 beat/min
   3. Tachypnea > 20/min or PaCO2 < 32 mmHg
   4. WBC count > 12 000/mm3 or < 4 000/mm3 or > 10% immature neutrophils (bands)

3. Consent to study inclusion, either by patient or legal surrogate before study-related sample processing

4. Study sample collection within 24 hours of ICU admission order

Exclusion Criteria:

1. Age less than 18 years old on the day of ICU admission
2. No order to admit to ICU
3. Not physically admitted to ICU
4. Commencement of non-prophylactic antibiotics ≥ 24 hours prior to ICU admission
5. Study sample collection > 24 hours from ICU admission order
6. No clinical cultures or serologic tests obtained when sepsis was suspected
7. Elective cardiac surgery patients with an expected duration in ICU of less than 24 hours
8. Transfer from another ICU where subject was admitted for ≥ 24 hours.

Patients suspected of sepsis, admitted to an Intensive Care Unit