Rapid point-of-care detection of SARS-CoV-2 infection in exhaled breath using ion mobility spectrometry: a pilot study.

BACKGROUND: An effective testing strategy is essential for pandemic control of the novel Coronavirus disease 2019 (COVID-19) caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Breath gas analysis can expand the available toolbox for diagnostic tests by using a rapid, cost-beneficial, high-throughput point-of-care test. We conducted a bi-center clinical pilot study in Germany to evaluate breath gas analysis using multi-capillary column ion mobility spectrometry (MCC-IMS) to detect SARS-CoV-2 infection. METHODS: Between September 23, 2020, and June 11, 2021, breath gas measurements were performed on 380 patients (SARS-CoV-2 real-time polymerase chain reaction (PCR) positive: 186; PCR negative: 194) presenting to the emergency department (ED) with respiratory symptoms. RESULTS: Breath gas analysis using MCC-IMS identified 110 peaks; 54 showed statistically significant differences in peak intensity between the SARS-CoV-2 PCR-negative and PCR-positive groups. A decision tree analysis classification resulted in a sensitivity of 83% and specificity of 86%, but limited robustness to dataset changes. Modest values for the sensitivity (74%) and specificity (52%) were obtained using linear discriminant analysis. A systematic search for peaks led to a sensitivity of 77% and specificity of 67%; however, validation by transferability to other data is questionable. CONCLUSIONS: Despite identifying several peaks by MCC-IMS with significant differences in peak intensity between PCR-negative and PCR-positive samples, finding a classification system that allows reliable differentiation between the two groups proved to be difficult. However, with some modifications to the setup, breath gas analysis using MCC-IMS may be a useful diagnostic toolbox for SARS-CoV-2 infection. TRIAL REGISTRATION: This study was registered at ClinicalTrials.gov on September 21, 2020 (NCT04556318; Study-ID: HC-N-H-2004).

A proof of concept study for the differentiation of SARS-CoV-2, hCoV-NL63, and IAV-H1N1 in vitro cultures using ion mobility spectrometry.

Rapid, high-throughput diagnostic tests are essential to decelerate the spread of the novel coronavirus disease 2019 (COVID-19) pandemic. While RT-PCR tests performed in centralized laboratories remain the gold standard, rapid point-of-care antigen tests might provide faster results. However, they are associated with markedly reduced sensitivity. Bedside breath gas analysis of volatile organic compounds detected by ion mobility spectrometry (IMS) may enable a quick and sensitive point-of-care testing alternative. In this proof-of-concept study, we investigated whether gas analysis by IMS can discriminate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from other respiratory viruses in an experimental set-up. Repeated gas analyses of air samples collected from the headspace of virus-infected in vitro cultures were performed for 5 days. A three-step decision tree using the intensities of four spectrometry peaks correlating to unidentified volatile organic compounds allowed the correct classification of SARS-CoV-2, human coronavirus-NL63, and influenza A virus H1N1 without misassignment when the calculation was performed with data 3 days post infection. The forward selection assignment model allowed the identification of SARS-CoV-2 with high sensitivity and specificity, with only one of 231 measurements (0.43%) being misclassified. Thus, volatile organic compound analysis by IMS allows highly accurate differentiation of SARS-CoV-2 from other respiratory viruses in an experimental set-up, supporting further research and evaluation in clinical studies.

Surgical trauma and postoperative immune dysfunction.

BACKGROUND: In postoperative sepsis, mortality is increased due to the surgically induced immune dysfunction. Further causes of this traumatic effect on the immune system include burn injuries and polytrauma, as well as endogenous traumata like stroke. Several animal models have been defined to analyse the characteristics of trauma-induced immune suppression. This article will correlate our results from animal studies and clinical observations with the recent literature on postoperative immune suppression. METHODS: The previously described model of surgically induced immune dysfunction (SID) was performed in mice by laparotomy and manipulation of the small intestine in the antegrade direction. Blood samples were collected 6 and 72 h following SID to analyse the white blood cell count and corticosterone levels. To assess the postoperative immune status in humans, we analysed expression of HLA-DR on monocytes of 118 patients by flow cytometry prior to and 24, 48 and 72 h after surgery. RESULTS: The postoperative immune suppression in our SID model is characterised by lymphocytopenia and significantly increased corticosterone levels in mice dependent on the degree of surgical trauma. This is comparable to the postoperative situation in humans: major and especially long-lasting surgery results in a significantly reduced expression of HLA-DR on circulating monocytes. Previous studies describe a similar situation following burn injury and endogenous trauma, i.e. stroke. CONCLUSIONS: We suggest the completion of our previously published sepsis classification due to the immune status at the onset of sepsis: type A as the spontaneously acquired sepsis and type B as sepsis in trauma-induced pre-existing immune suppression.