The Role of Procalcitonin, C-reactive Protein and White Blood Cells in the Differential Diagnosis Between Sepsis and SIRS in Cardiac Surgery Patients

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.