Objectives: The aim of the study was to evaluate the role of procalcitonin (PCT), C-reactive
protein (CRP), and white blood cells (WBCs) in the differential diagnosis between
sepsis and systemic inflammatory response syndrome (SIRS).
Methods: We retrospectively analyzed 2,834 consecutive patients after cardiac surgery operated
between January 2012 and December 2017. From the whole cohort, we identified two groups
based on the postoperative characteristics: patients with sepsis (44 patients) and
patients with a diagnosis of SIRS (40 patients). From the two groups were excluded
patients with endocarditis, patients treated preoperatively with corticosteroid, those
who developed an infection in the ward, and patients who died in the first 48 hours.
Measurements of PCT, CRP, and WBCs were analyzed for the first 5 postoperative days.
Results: Patients who developed sepsis had a higher rate of reoperation during the stay in
the intensive care unit (ICU) compared with the SIRS group (40.9% of patients with
sepsis vs. 10.0% with SIRS, p = 0.0036). Patients with sepsis had also a longer postoperative length of stay in
the ICU (21.3 vs. 4.42 days, p < 0.0001) and were more likely to die in hospital (43.2% of patients with sepsis
vs. 7.5% with SIRS, p = 0.00053). The mean values of PCT in patients with sepsis and SIRS were not statistically
different at any time point. In our data, CRP values were consistently higher in patients
with sepsis from the third to the fifth postoperative day (p = 0.05, p = 0.00064, and p < 0.0001, respectively). In patients with sepsis, WBCs mean values were lower in
the first postoperative day (p = 0.0044) but higher in the fifth (p = 0.01).
Conclusion: CRP is a reliable value in the challenging diagnosis between sepsis and SIRS after
cardiac surgery, especially after the second postoperative day. On the contrary, preliminary
results suggest that PCT and WBCs are less useful to this differential diagnosis.
However, high missingness rates and effect interactions must still be explored. We
started a prospective study to improve our understanding of the role of blood sample
in postoperative sepsis and SIRS.