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Signa Vitae

Journal of Intensive Care and Emergency Medicine

Diagnostic markers of serious bacterial infections in infants aged 29 to 90 days

Abstract

Objectives: The diagnosis of serious bacterial infection (SBI) is difficult due to a lack of clinical evidence. The purpose of this study was to determine which inflammatory markers can be used to detect SBI in febrile infants.

Methods: This retrospective cohort study included infants aged 29 to 90 days who visited a tertiary hospital emergency department in Korea between July 2016 and June 2018. The diagnostic characteristics of the neutrophil-to-lymphocyte ratio (NLR), procalcitonin (PCT), C-reactive protein (CRP), white blood cell (WBC) count, and absolute neutrophil cell (ANC) count for detecting SBI were described. Their cutoff values were calculated based on receiver operating characteristic (ROC) curve analysis.

Results: Among 528 infants, 199 were finally enrolled. SBI was detected in 68 (34.2%) of these infants. The median values of all investigated diagnostic markers were significantly higher in infants with SBI than the values in those without: WBC (12.72 vs. 9.91 k/μL), ANC (6.28 vs. 3.14 k/μL), CRP (26.6 vs. 2.8 mg/L), NLR (1.29 vs. 0.78), and PCT (0.5 vs. 0 ng/mL). The areas under the ROC curves for discriminating SBI were: 0.705 (95% confidence interval [CI], 0.629-0.781), 0.793 (95% CI, 0.731-0.856), 0.832 (95% CI, 0.775-0.889), 0.722 (95% CI, 0.651-0.792), and 0.695 (95% CI, 0.611-0.780) for WBC, ANC, CRP, NLR, and PCT, respectively. Using a cutoff value of 0.67 for NLR, the negative predictive value was 90.8% for identifying SBI.

Conclusions: CRP was the best single discriminatory marker of SBI, while NLR was the best parameter for considering discharge.

Key words: bacterial infection, urinary tract infection, clinical marker, discharge planning

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Procalcitonin – potential, limitations and availability

Abstract

Bacterial infections and sepsis are major problems in critically ill patients. Timely diagnosis and therapy reduce morbidity and mortality. Many studies have included the investigation of various biomarkers whose elevated concentrations can indicate sepsis; among them, PCT proved to be most useful.

PCT is synthesized in the thyroid gland as a prohormone of calcitonin. In healthy individuals the PCT concentration is <0.1 ng/mL.

The advantage of the PCT is a high negative predictive value for the exclusion of sepsis, with the cut-off value of 0.5 ng/ml. A concentration between 2 and 10 ng/ml indicates strong sepsis, whereas a value ≥10 ng/ml is associated with septic shock. In addition to the diagnosis of sepsis, the measurement of PCT concentration is useful for the introduction and monitoring of antibiotic therapy, which is performed according to an algorithm based on the cut-off value for PCT.

Immunoassays are used to measure PCT concentrations in serum or plasma. It is possible to determine the concentration in whole blood by using point-of-care testing.

In pathological conditions that are not associated with sepsis, PCT is useful as a prognostic indicator of disease complications. Some studies suggest that PCT is a potential early indicator of acute coronary syndrome.

Key words: procalcitonin, bacterial infection, sepsis, intensive care unit

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