Diagnostic and prognostic role of calprotectin levels in patients with sepsis monitored in the intensive care unit: A prospective study

Introduction and Objective: Sepsis is a syndrome of life-threatening organ dysfunction caused by a dysregulated host response to infection. Early diagnosis of sepsis can facilitate the initiation of rapid and appropriate therapeutic interventions, thereby reducing sepsis-related morbidity and mortality. However, distinguishing sepsis from non-infectious conditions (such as trauma, burn, hemorrhage, hypothermia, pancreatitis, and surgery) and making a rapid diagnosis can be challenging. Sepsis biomarkers are used to assess disease severity and predict prognosis in the early stages of the disease. However, more reliable biomarkers with higher sensitivity and specificity are needed for the early diagnosis and treatment of sepsis. This study aims to evaluate the role of calprotectin (CLP) in the diagnosis of sepsis, its use in monitoring antimicrobial therapy, and its relationship with mortality. Materials and Methods: This prospective study included 36 patients diagnosed with sepsis in the internal medicine intensive care unit of Afyonkarahisar University of Health Sciences Hospital between July 1, 2023, and July 1, 2024. The control group 1 consisted of trauma patients in the anesthesia and reanimation intensive care unit who met the systemic inflammatory response syndrome (SIRS) criteria but had no identified infectious focus. Control group 2 consisted of healthy volunteers who visited the family medicine outpatient clinic for routine health check-ups. The following parameters were monitored: white blood cell (WBC) count, procalcitonin (PCT), C-reactive protein (CRP), CLP level, APACHE II (Acute Physiology and Chronic Health Evaluation) score, SOFA (Sequential Organ Failure Assessment) score, neutrophil/lymphocyte ratio (NEU/LENF), Lactate levels, and patient status. In the study group, parameters were recorded on the day of sepsis diagnosis (Day 1), as well as on Days 3, 5, 7, and 10 after the initiation of appropriate empirical antimicrobial therapy. In the control groups, parameters were recorded only once at the time of presentation. The obtained data were statistically analyzed and compared. Results: In the ROC analysis performed by comparing the mean CLP value in the control groups with the mean CLP value of the patients in the study group at the time of diagnosis, the cut-off value for sepsis diagnosis was calculated as 44.02 ng/L.The sensitivity and specificity for this value were both calculated as 52.8%. The mean CLP level on the first day in the study group was 44.47 ng/mL, while it was 43.42 ng/mL in control group 2, with no significant difference between them (p > 0.05). When the trends of CLP levels were examined in correlation with other biomarkers over time, no statistically significant relationship was found between CLP and CRP, PCT, or WBC (p > 0.05). Conclusion: Serum CLP levels alone are considered an insufficient biomarker for distinguishing sepsis patients from other inflammatory conditions. Due to its susceptibility to various influencing factors, CLP is not an ideal biomarker for diagnosing sepsis or predicting mortality. Further studies with larger populations, investigating CLP levels in body fluids obtained from the infection site in sepsis patients, are needed.