News in Laboratory Diagnostics of Early Sepsis − First Czech Experiences
Sepsis represents one of the most frequent causes of morbidity and mortality in critically ill patients. Laboratory markers play an important role in the diagnosis and prognosis of septic states. The aim of the study by the Czech authors was to evaluate the diagnostic yield of new laboratory markers in the form of monocyte distribution width and specific markers on the surface of neutrophil granulocytes.
Introduction
In infectious diseases, neutrophils and monocytes play a role in the first line of the immune response. Monocytes activate when fighting an infectious agent, increase the intracellular content of lysosomes, and thus change their size. An increase in the value of the so-called monocyte distribution width reflects their activity during an infectious disease.
A great advantage of this examination is the direct determination of the value within the basic blood count with a differential leukocyte count, which can be performed on a special laboratory analyzer. According to a multicenter study conducted by the manufacturer, the cut-off value is 20 units, with an increase above this value in adult patients associated with a higher probability of developing sepsis within 12 hours.
Another promising method in laboratory diagnostics of early sepsis is the determination of the intensity of expression of surface markers CD64 and CD11b on the surface of neutrophils using flow cytometry. When exposed to pro-inflammatory cytokines and bacterial agents, the expression of surface markers significantly increases, while in a resting state, they are present on the surface of neutrophils only in small amounts.
Methodology and Course of the Study
From November 2019 to June 2020, a unique study was conducted at the General University Hospital in Prague, focusing on comparing inflammatory laboratory markers and evaluating their diagnostic yield for early sepsis. Definitive results of the study are not yet available; their processing and preparation for publication is still ongoing.
In addition to the above-mentioned new parameters, already used biochemical inflammation parameters (CRP, lactate, procalcitonin, interleukin IL-6, and presepsin) and hematological inflammation parameters (based on the blood count) were also determined for the study. The hematological examination was extended by the Intensive Care Infection Score (ICIS) parameter, which helps to distinguish sepsis from non-infectious systemic inflammatory response syndrome (SIRS) and is calculated from 5 parameters reflecting the early immune response to infectious agents.
Data from 104 patients were retrospectively evaluated in the study, who were divided into the following groups based on clinical findings and laboratory results: sepsis/septic shock (n = 40), localized infection (n = 35), non-infectious SIRS (n = 14), controls without localized or systemic inflammation (n = 15).
Preliminary Results
The value of monocyte distribution width in septic patients correlated well with leukocyte growth and left shift, but the correlation between MDW and ICIS score was rather variable. The behavior of both parameters towards the value of procalcitonin was also similar. Neither parameter alone had a clear specificity for laboratory diagnosis of sepsis.
However, the behavior of the MDW parameter indicated that it is a better diagnostic parameter for septic states with one undeniable advantage, namely the quick and inexpensive determination within a blood count examination. An interesting finding was the MDW values in the control group, which were around the cut-off value of 20 and in some cases reached up to 24.
During the interim evaluation, the surface marker CD64 on neutrophil granulocytes also appeared very promising, especially in combination with the value of procalcitonin. The fluorescence intensity of the CD64 marker helped distinguish between the septic and control group fairly well, with the septic group having an increase of up to 10×. Conversely, the determination of the CD11b marker on neutrophils does not appear, based on preliminary results, to be a suitable method for diagnosing septic states in adults, often with multiple comorbidities.
Conclusion
From the preliminary results of the study, it appears that the evaluation of monocyte distribution width could become a valuable tool in diagnosing early cases of sepsis in the future, not only due to the simplicity and rapid feasibility of this examination.
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Source: Francová I., Vášová V., Lahoda Brodská H. News in laboratory diagnostics of early sepsis. In vitro diagnostics 2021; 39: 34−36.
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