ABSTRACT
Face masks and personal respirators are used to curb the transmission of SARS-CoV-2 in respiratory droplets; filters embedded in some personal protective equipment could be used as a non-invasive sample source for applications, including at-home testing, but information is needed about whether filters are suited to capture viral particles for SARS-CoV-2 detection. In this study, we generated inactivated virus-laden aerosols of 0.3-2 microns in diameter (0.9 µm mean diameter by mass) and dispersed the aerosolized viral particles onto electrostatic face mask filters. The limit of detection for inactivated coronaviruses SARS-CoV-2 and HCoV-NL63 extracted from filters was between 10 to 100 copies/filter for both viruses. Testing for SARS-CoV-2, using face mask filters and nasopharyngeal swabs collected from hospitalized COVID-19-patients, showed that filter samples offered reduced sensitivity (8.5% compared to nasopharyngeal swabs). The low concordance of SARS-CoV-2 detection between filters and nasopharyngeal swabs indicated that number of viral particles collected on the face mask filter was below the limit of detection for all patients but those with the highest viral loads. This indicated face masks are unsuitable to replace diagnostic nasopharyngeal swabs in COVID-19 diagnosis. The ability to detect nucleic acids on face mask filters may, however, find other uses worth future investigation.
Subject(s)
COVID-19/pathology , Masks/virology , Nasopharynx/virology , SARS-CoV-2/isolation & purification , Adult , Aerosols , Aged , COVID-19/virology , Female , Hospitalization , Humans , Limit of Detection , Male , Middle Aged , Particle Size , RNA, Viral/analysis , Real-Time Polymerase Chain Reaction , SARS-CoV-2/physiology , Static Electricity , Viral Load , Young AdultABSTRACT
OBJECTIVE: Diagnosing residual malignancy after (chemo)radiotherapy presents a diagnostic challenge because of overlapping symptoms and imaging characteristics. We assessed the added diagnostic value of diffusion-weighted imaging (DWI) to positron emission tomography combined with computed tomography (PET-CT) in patients with head and neck squamous cell carcinoma (HNSCC) with residual fluorodeoxyglucose (18F-FDG) uptake at the primary tumor site 3 months after (chemo)radiotherapy. STUDY DESIGN: For this retrospective study from January 2010 to June 2012, 22 cases (median patient age of 61 years; range 41-77 years) were included for analysis. Both PET-CT and magnetic resonance imaging (MRI), including DWI, were performed as part of the institutional protocol and were qualitatively assessed for the presence of residual malignancy at the primary tumor site. RESULTS: The sensitivity and specificity of PET-CT were 100% and 47%, respectively. For DWI, sensitivity and specificity were 80% and 82%, respectively. When DWI was added to PET-CT with residual 18F-FDG uptake, and only a positive read on both PET-CT and DWI was considered to be overall positive, sensitivity remained 80% (95% confidence interval [CI] 28%-99%), and specificity was 88% (95% CI 64%-99%). CONCLUSIONS: In this pilot study of the selected patients with residual 18F-FDG uptake at the primary tumor site 3 months after (chemo)radiotherapy, we demonstrated that the addition of DWI to PET-CT has the potential to increase the specificity of the response evaluation with limited decrease in sensitivity.
