The swab site of the upper airways influences the diagnostic sensitivity for the omicron variant of SARS-CoV-2

The cycle-threshold-value (CT -value) is a quantitative value of the polymerase chain reaction (PCR), which represents the gold standard for the detection of severe acute respiratory syndrome coronavirus 2 (SARS CoV 2). The CT -value can be used to indicate the viral load in swabs of the airways. The collection of a specimen is the only part of the testing process, which is performed manually and carries, therefore, a high potential for increasing measurement variability. The comparison of different PCR results is often difficult since the exact swabbing technique of each test and how do swabs relate in a direct comparison is unknown. For these reasons, the infection course in a patient can be hard infer even after multiple swabs. As the Omicron variant spread from 06/2022 to 08/2022, all common modalities of the upper airway swabs (nasopharyngeal, oropharyngeal, combined naso-oropharyngeal, nasal orifice swabs as well as swabs of the buccal mucosa), which were performed on patients with a suspected infection with SARS CoV 2. RT-PCR was used for SARS CoV 2 RNA detection and the sample comparison was based on the CT -values obtained. Viral loads can vary significantly depending on the swab sites of the upper airways. For the maximum clinical sensitivity, a combined naso-oropharyngeal swab should be considered. In case a single point and single sample measurement is the norm, a nasopharyngeal swab can deliver the highest viral load at the presumed beginning of the infection. Furthermore, the findings of this study can be valuable to correctly interpret results of different PCR with different sampling techniques.

Frontline Science: Aggregated neutrophil extracellular traps prevent inflammation on the neutrophil-rich ocular surface

Eye rheum is a physiological discharge, which accumulates at the medial angle of the healthy eye soon after opening in the morning. Microscopic evaluation of eye rheum revealed the presence of viable neutrophils, bacteria, epithelial cells, and particles, aggregated by neutrophil extracellular traps. We observed that in the evening, during eye closure, high C5a recruited neutrophils to the tear film and activated them. In this hypoxic area rich in CO₂ , neutrophils fight microbial aggressors by degranulation. Immediately after eye opening, the microenvironment of the ocular surface changes, the milieu gets normoxic, and loss of CO₂ induces subtle alkalinization of tear film. These conditions favored the formation of neutrophil extracellular traps (NETs) that initially covers the ocular surface and tend to aggregate by eyelid blinking. These aggregated neutrophil extracellular traps (aggNETs) are known as eye rheum and contain several viable neutrophils, epithelial cells, dust particles, and crystals packed together by NETs. Similar to aggNETs induced by monosodium urate crystals, the eye rheum shows a robust proteolytic activity that degraded inflammatory mediators before clinically overt inflammation occur. Finally, the eye rheum passively floats with the tear flow to the medial angle of the eye for disposal. We conclude that the aggNETs-based eye rheum promotes cleaning of the ocular surface and ameliorates the inflammation on the neutrophil-rich ocular surfaces.

[Stress fracture of the calcaneus following aerobic gymnastics]

A stressfracture of the calcaneus after aerobic-gymnastic was observed. In comparance with stressfractures of different localisation there is only little of periostal callus. The leading radiological is spongiosasclerosis.