Clinical diagnosis of sepsis and the combined use of biomarkers and culture- and non-culture-based assays

Volume, conductivity, and scatter parameters of leukocytes as early markers of sepsis and treatment response

INTRODUCTION:

Morphologic changes in the size and granularity of leukocytes seen in sepsis could be measured using the volume, conductivity, and scatter (VCS parameters) from the automated hematology analyzers. The objective of this study is to find the clinical usefulness of VCS parameters as possible indicators of sepsis and to determine the effect of treatment on these parameters.

METHODS:

This observational study was conducted in a tertiary level hospital in India. Hemogram and VCS parameters obtained from LH 750 (Beckman coulter, Fullerton, CA) from 134 proven blood culture-positive cases of sepsis were reviewed on the day of culture positivity (day 0), day 3, and day 7 were analyzed and compared with those of samples from otherwise healthy 100 participants. Statistical analysis of data was done, and cutoff value was established using receiver-operator characteristic curve.

RESULTS:

Out of 134 culture-positive cases, 55.2% (n = 74) Gram-negative and 44.8% (n = 60) Gram-positive bacteria were isolated. The mean neutrophil volume (MNV) and mean monocyte volume (MMV) were higher in the sepsis group compared to that of the control group (165.43 ± 18.21 vs. 140.59 ± 7.6, P = 0.001 for MNV and 179.8 ± 14.16 vs. 164.54 ± 9.6, P = 0.001 for MMV). A significant decrease in MNV and MMV was observed with the initiation of the treatment. Significant changes in scatter and conductivity parameters were also noticed. A cutoff value of 150.2 for MNV gave a sensitivity and specificity of 79.1% and 95%, respectively, with an area under the curve (AUC) of 92.3%. With a cutoff of 168.3, MMV had a sensitivity of 80.6% and specificity of 77.5%, AUC of 83%.

CONCLUSION:

VCS parameters such as MNV and MMV can be easily obtained by an automated hematology analyzer and could be used for early detection and therapeutic response in sepsis.

Enhanced Signal Amplification in a Toll-like Receptor-4 Biosensor Utilizing Ferrocene-Terminated Mixed Monolayers

A major challenge in effectively treating infections is to provide timely diagnosis of a bacterial or viral agent. Current cell culture methods require >24 h to identify the cause of infection. The Toll-like Receptor (TLR) family of proteins can identify classes of pathogens and has been shown to work well in an impedance-based biosensor, where the protein is attached to an electrode via a self-assembled monolayer (SAM). While the sensitivity of these sensors has been good, they contain a high resistance (>1 kΩ) SAM, generating relatively small signals and requiring longer data collection, which is ill-suited to implementation outside of a laboratory. Here, we describe a novel approach to increase the signal magnitude and decrease the measurement time of a TLR-4 biosensor by inserting a redox-active ferrocenyl-terminated alkanethiol into a mixed SAM containing hydroxyl- and carboxyl-terminated alkanethiols. The SAM formation and modification was confirmed via contact angle and X-ray photoelectron spectroscopy measurements, with TLR-4 immobilization demonstrated through a modified immunosorbent assay. It is shown that these TLR-4 biosensors respond selectively to their intended target, Gram-negative bacteria at levels between 1 and 10⁵ lysed cells/mL, while remaining insensitive to Gram-positive bacteria or viral particles at up to 10⁵ particles/mL. Furthermore, the signal enhancement due to the addition of ferrocene decreased the measurement time to less than 1 min and has enabled this sensor to be used with an inexpensive, portable, hand-held potentiostat that could be easily implemented in field settings.

Tumor Cell Detection by Mass Spectrometry Using Signal Ion Emission Reactive Release Amplification

A method is presented for the detection of circulating tumor cells (CTC) using mass spectrometry (MS), through reporter-ion amplification. Particles functionalized with short-chain peptides are bound to cells through antibody-antigen interactions. Selective release and MS detection of peptides is shown to detect as few as 690 cells isolated from a 10 mL blood sample. Here we present proof-of-concept results that pave the way for further investigations.

Expression of CD11c and EMR2 on neutrophils: potential diagnostic biomarkers for sepsis and systemic inflammation

There is a need for cellular biomarkers to differentiate patients with sepsis from those with the non-infectious systemic inflammatory response syndrome (SIRS). In this double-blind study we determined whether the expression of known (CD11a/b/c, CD62L) and putative adhesion molecules [CD64, CD97 and epidermal growth factor (EGF)-like molecule containing mucin-like hormone receptor (EMR2)] on blood neutrophils could serve as useful biomarkers of infection and of non-infectious SIRS in critically ill patients. We studied 103 patients with SIRS, 83 of whom had sepsis, and 50 healthy normal subjects, using flow cytometry to characterize neutrophils phenotypically in whole blood samples. Patients with SIRS had an increased prevalence of neutrophils expressing CD11c, CD64 and EMR2 in comparison with healthy subjects (P < 0.001), but normal expression of CD11a, CD11b, CD62L and CD97. An increase in the percentage of neutrophils bearing CD11c was associated with sepsis, EMR2 with SIRS and CD64 with sepsis and SIRS. Neutrophils expressing CD11c had the highest sensitivity (81%) and specificity (80%) for the detection of sepsis, and there was an association between the percentage of neutrophils expressing EMR2 and the extent of organ failure (P < 0.05). Contrary to other reports, we did not observe an abnormal expression of CD11b or CD62L on neutrophils from patients with SIRS, and suggest that this discrepancy is due to differences in cell processing protocols. We propose that blood neutrophils expressing CD11c and EMR2 be considered as potential biomarkers for sepsis and SIRS, respectively.

Soluble urokinase-type plasminogen activator receptor (suPAR) – a possible biomarker for bacteremia in sepsis / Forma solubilă a receptorului pentru activatorul de plasminogen de tip urokinază (suPAR) – un biomarker posibil pentru bacteriemie în sepsis

Background. Validating new sepsis biomarkers can contribute to early diagnosis and initiation of therapy. The aim of this study is to evaluate the sepsis predictive capacity of soluble urokinase plasminogen receptor (suPAR) and its role in evaluating the prognosis of bloodstream infections. Material and method. We conducted a prospective pilot study on 49 systemic inflammatory response syndrome (SIRS) patients admitted to the intensive care unit (ICU), that were divided, on the basis of bacteremia in group A (SIRS with bacteremia, n=14) and group B (SIRS without bacteremia, n=35). Hemoculture and blood samples were drawn on the first day to determine suPAR, C-reactive protein (CRP) and procalcitonin (PCT). We set to identify significant cut-off values in estimating bacteremia and mortality in septic patients. Results. In group A, suPAR values were 14.3 ng/mL (range 10-45.5 ng/mL) and in group B, 9.85 ng/mL (range 3.4-48 ng/mL) p=0.008. Area under the curve (AUC) for suPAR was 0.745 (95% CI: 0.600-0.859), for CRP 0.613 (95% CI: 0.522-0.799) and for PCT 0.718 (95% CI: 0.477-0.769). Cut-off value for suPAR in bacteremia prediction was 9.885 ng/mL, with 100% sensibility and 51.43% specificity. Mortality in group A was 85.7% (12/14) and in group B 74.3% (26/39), p>0.05. Area under the curve (AUC) for suPAR was 0.750 (95% CI: 0.455-0.936), for CRP 0.613 (95% CI: 0.413-0.913) and for PCT 0.618 (95% CI: 0.373-0.888). Cut-off value of suPAR in predicting mortality was 11.5 ng/mL, with 66.67% sensibility and 100% specificity. Conclusions. In our study suPAR had a predictive capacity for bacteremia and seems to be an independent factor for mortality prognosis in septic patients.