The Unknown Sequential Behavior of Neutrophil Extracellular Traps in Parapneumonic Effusions

According to Twaddell et al1Twaddell S.H. Gibson P.G. Grainge C. Baines K.J. Parapneumonic effusions are characterized by elevated levels of neutrophil extracellular traps.Chest. 2021; 160: 1645-1655Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar in an article published in CHEST (November 2021), concentrations of neutrophil extracellular trap (NET)-related mediators were significantly higher in the parapneumonic effusions than those of other origins. Thus, the use of these markers would enable physicians to diagnose parapneumonic effusions more clearly. Besides, the results of this study suggest the potential therapeutic benefit of deoxyribonuclease in parapneumonic effusions and empyema. However, we would like to raise one question: Do these markers fluctuate over time due to disease progression? The authors clarified how to collect pleural fluid samples in their study, but not when. Although it is very complicated to tell the onset of parapneumonic effusions or empyema, it would matter whether the samples were collected on admission or a few days later. It also seems critical whether these samples were obtained before or after antibiotic administration. In short, the timing of sample collection is essential when discussing acute inflammatory reactions and inflammatory-related markers. For example, C-reactive protein can fluctuate by the day. The peak concentrations of this protein have been known to reach from 36 to 50 hours after the onset of infection.2Lelubre C. Anselin S. Zouaoui Boudjeltia K. Biston P. Piagnerelli M. Interpretation of C-reactive protein concentrations in critically ill patients.Biomed Res Int. 2013; 2013: 124021Crossref PubMed Scopus (77) Google Scholar Thus, it is sometimes confusing to interpret C-reactive protein levels in the acute phase of infectious diseases. NET-related mediators do not seem to be an exception to this type of issue. Furthermore, it is also challenging to determine the onset of underlying disorders in malignant and transudative effusions cases. Ultimately, it seems undeniable that NET-related mediators were elevated in these cases if samples were collected soon after the onset. We believe uncovering the sequential behavior of NET-related mediators would enable physicians and researchers to use them more effectively. Therefore, further studies should be accumulated to clarify the behavior of these mediators and to determine clinical settings in which they are helpful. Parapneumonic Effusions Are Characterized by Elevated Levels of Neutrophil Extracellular TrapsCHESTVol. 160Issue 5PreviewHigh levels of some NET-related mediators in parapneumonic effusions correlate with inflammation. Effusions of other causes do not show high levels of NETs. These results may have treatment implications because NETs may be an important contributor to the inflammation and viscosity of parapneumonic effusions and may help us to understand the therapeutic benefit of deoxyribonuclease in empyema. Full-Text PDF ResponseCHESTVol. 161Issue 4PreviewWe thank Drs Ito and Ogawa for their considered attention to our article.1 We agree there remains much that is unknown about the onset and progression of neutrophil extracellular traps (NETs) in parapneumonic and other effusions. We expect that NETs levels will fluctuate within effusions over time (in keeping with other circumstances in which they are seen2,3); however, the degree and timing is, as far as we are aware, unknown. Full-Text PDF