[Diagnostic value of serum procalcitonin for infection in the immunocompromised critically ill patients with suspected infection].

OBJECTIVE: To evaluate the diagnostic and prognostic value of the serum procalcitonin (PCT) level in the non-acquired immune deficiency syndrome (AIDS) immunocompromised critically ill patients suspected to have infection.

METHODS: A retrospective study was conducted in the non-AIDS immunocompromised patients who were admitted to Department of Critical Care Medicine of Xiangya Hospital, Central South University during January 2011 to December 2014. Demographic characteristics, underlying disease, acute physiology and chronic health evaluation II (APACHEII) score at admission, and clinical records including baseline and peak levels of temperature, white blood count (WBC), PCT, and survival rate within 28 days, infection focus, infectious agents (bacterial, fungi or mixed infection), and the severity of infection (sepsis, severe sepsis, or septic shock) were recorded. Receiver operating characteristic (ROC) curve was plotted, and the diagnostic and protective value of above parameters was evaluated.

RESULTS: A total of 98 patients (43 male and 55 female) were enrolled in the study with a median age of 44 (28, 52) years old and a median APACHEII score of 17 (11, 20); 47 with malignant hematological tumor, 45 with autoimmune diseases, and 6 post solid organ transplantation. Among them 53 patients (54.1%) died within 28 days. Twenty-seven patients were diagnosed as systemic inflammatory response syndrome (SIRS) without infection. Among 71 patients with infection, 45 were diagnosed as bacterial infection, 10 with fungal infection, and 16 with mixed infection. Sepsis was diagnosed in 7 patients, severe sepsis in 32 patients, and septic shock in 32 patients. (1) There was no statistical significance in the baseline and peak levels of PCT and WBC, or baseline level of temperature between the groups of SIRS patients without infection and infected patients. The peak level of temperature was significantly higher in the patients with infection as compared with that of the SIRS without infection patients [centigrade: 39.4 (38.9, 40.0) vs. 38.8 (37.8, 39.2), Z=-3.268, P=0.001]. It was showed by subgroup analysis that in patients with hematological malignant disease or autoimmune diseases, higher level of body temperature was found in infection group compared with non-infection SIRS group [centigrade: 39.5 (39.0, 40.0) vs. 39.0 (38.4, 39.4), Z=-2.349, P=0.019; 39.0 (38.4, 39.5) vs. 38.2 (37.0, 38.9), Z=-2.221, P=0.026]. (2) The baseline level of PCT (μg/L) were 0.54 (0.20, 4.19), 2.78 (0.50, 9.54), 1.00 (0.45, 6.89), and 0.22 (0.07, 1.86) in non-infection SIRS patients or the patients with bacterial, fungal, and mixed infection, respectively. The peak level of PCT (μg/L) were 4.19 (1.95, 13.42), 12.37 (3.82, 45.89), 1.82 (0.49, 17.86), and 5.14 (2.66, 12.62), respectively, in each subgroup. When the comparison was conducted among the patients with different infectious agent, the baseline level of PCT in patients with bacterial infection was significantly higher than that in SIRS patients without infection (P=0.026) and mixed infection patients (P=0.001), and the peak level of PCT was significantly higher than that in the SIRS patients without infection (P=0.009) and the patients with fungal infection (P=0.016). ROC curve showed that the higher value was found in the baseline and peak levels of PCT for diagnosis of septic shock in all patients [ area under ROC curve (AUC) of baseline level=0.681±0.054, P=0.001; AUC of peak level=0.690±0.054, P=0.002], and the same value was also found in the baseline and peak levels of PCT for diagnosis of bacterial infection in the patients with malignant hematological tumor (AUC of baseline level=0.687±0.080, P=0.008; AUC of peak level=0.697±0.079, P=0.021). (3) The peak level of PCT (μg/L) were 4.05 (0.53, 31.22), 5.78 (2.14, 16.68), and 11.64 (2.94, 58.14) in subgroup of patients with sepsis, severe sepsis and septic shock, respectively, and they showed no statistical significance among subgroups (P>0.05). A high serum level of peak PCT strongly indicated the presence of septic shock (AUC=0.646±0.060, P=0.019), especially in the subgroup of patients with systemic autoimmune disease (AUC=0.689±0.081, P=0.035). (4) The peak level of PCT (μg/L) in the APACHEII>18 group (38 cases) was significantly higher than that of APACHEII≤18 group [ 60 cases, PCT (μg/L): 11.64 (3.36, 39.39) vs. 4.42 (1.32, 14.70), P=0.016]; there was a certain correlation between the peak level of PCT and the severity of the disease. (5) The peak level of PCT in death group was significantly higher than that of the survival group [μg/L: 9.07 (3.05, 33.09) vs. 4.19 (1.26, 14.61), P=0.043]. ROC curve showed that the peak level of PCT might be valuable in predicting the prognosis in immunocompromised patients (AUC=0.619±0.057, P=0.043).

CONCLUSIONS: The serum level of PCT is found to be a reliable marker for the diagnosis of bacterial infection in immunocompromised critical patients, especially in those with hematologic malignancy. Additionally, PCT provides a useful tool for evaluating the severity of infection and the prognosis of critically ill patients.