Use of procalcitonin in diagnosis and follow-up in patients hospitalized in the intensive care unit who develop bacteremia / candidemia

Sepsis and bacteremia/candidemia are frequently seen infections in intensive care unit (ICU) settings and they are significant causes of mortality. In these patients early treatment can be life saving. It takes time to grow bacteria and to diagnose bacteremia with current blood culture systems. So, this study was performed to answer the question of whether procalcitonin can predict bacteremia before the blood culture test was concluded and compare PCT with fever and other infection markers. Between January 2019 and March 2020, among patients hospitalized in primary, secondary or tertiary intensive care units the following features and findings of those patients with suspected infection and who had blood culture were recorded: procalcitonin (PCT), CRP, white blood cell (WBC) count, neutrophil/lymphocyte (N/L) ratio, platelet and lactate test results concomitant with blood culture collection, infection site, clinical and laboratory signs associated with sepsis. Patients with positive blood culture were compared with patients without in terms of body temperature, PCT, CRP lactate levels, WBC count and N/L ratio. The optimum cut off values of markers showing significant difference between groups were determined by the receiver operating characteristics curves (ROC) analysis. When these cut-offvalues were applied, sensitivity, specifity, positive predictive (PPV) and negative predictive values (NPV) of markers to predict bacteremia/candidemia were also determined. Blood culture growth occurred in 60 of 155 patients. When patients with positive blood culture were compared patients without, PCT test results taken at the same day of blood culture showed significant difference between groups while no significant difference was detected in terms of laboratory markers including WBC, N/L, CRP, lactate and platelet count. Median PCT level in patients with positive blood culture was 3 ng/ml while it was 1,38 ng/ml in patients without blood culture positivity (p=0,034). Among paremeters obtained at antibiotic initiation, PCT levels, body temperature and SOFA scores were found to be significinatly higher in bacteremic patients than nonbacteremic patients. The mean of body temperature of bacteremic patients was found to be higher than others (37,81±0,87°C vs 37,36±0,86°C, p=0,001). Optimum PCT and body temperature cut off values to diagnose bacteremia/candidemia were found to be 2,18 ng/ml and 37,8°C after ROC analysis was performed (area under curve (AUC) for PCT 0,63, p=0,025; AUC for body temperature 0,66, p<0,001). At these cut off levels sensitivity, specifity, PPV and NPV's of PCT and body temperature to predict bacteremia were as follows respectively: %62,7, %60, %49, %72 for PCT and %56,7, %74,5, %58,6, %72,9 for body temperature. The optimum cut off of SOFA score was found to be 10. When patients with gram negative bacteremia (GNB) compared with all other patients, it was found that only PCT and body temperature can distinguish patients with Gram negative bacteremia from others (median of PCT level taken on the same day of blood culture was 4,77 while 1,48 in other patients, p=0,037). ROC analysis revealed that the optimum thresholds of PCT and body temperature for diagnosis of GNB were 2,18 ng/ml and 37,8°C (AUC's for both markers were approximately 0,63). Sensitivity, specifity, PPV and NPV of PCT at a cut off of 2,18 ng/ml to diagnose GNB were found to be %78,57, %57,94, %29,33 ve %92,41 respectively. NPV of fever<37,8°C was determined as %88,5. In conclusion, in ICU settings, among patients with suspected infection, fever and PCT levels are usefull in diagnosing bacteremia/candidemia. Patients with GNB had higher PCT levels, therefore the cut off of 2,18 ng/ml which is determined as the optimum cut off for distinguishing bacteremic patients from nonbacteremic ones, is very usefull to exclude GNB. Higher PCT levels show higher spesifity for GNB. Key words: Bacteremia, C-reactive protein, Candidemia, Procalcitonin, Intensive care infection