Rapid antigen test as a tool for the identification of SARS-CoV-2 infection and its potential as a self-testing device

ABSTRACT Background: SARS-CoV-2 virus originated in Wuhan (China) in December (2019) and quickly spread worldwide. Antigen tests are rapid diagnostic tests (RDT) that produce results in 15-30 min and are an important tool for the scale-up of COVID-19 testing. COVID-19 diagnostic tests are authorized for self-testing at home in some countries, including Brazil. Widespread COVID-19 diagnostic testing is required to guide public health policies and control the speed of transmission and economic recovery. Methods: Patients with suspected COVID-19 were recruited at the Hospital da Baleia (Belo Horizonte, Brazil). The SARS-CoV-2 antigen-detecting rapid diagnostic tests were evaluated from June 2020 to June 2021 using saliva, nasal, and nasopharyngeal swab samples from 609 patients. Patient samples were simultaneously tested using a molecular assay (RT-qPCR). Sensitivity, specificity, accuracy, and positive and negative predictive values were determined using the statistical program, MedCalc, and GraphPad Prism 8.0. Results: The antigen-detecting rapid diagnostic tests displayed 98% specificity, 60% sensitivity, 96% positive predictive value, and moderate concordance with RT-qPCR. Substantial agreement was found between the two methods for patients tested < 7 days of symptom onset. Conclusions: Our findings support the use of Ag-RDT as a valuable and safe diagnostic method. Ag-RDT was also demonstrated to be an important triage tool for suspected COVID-19 patients in emergencies. Overall, Ag-RDT is an effective strategy for reducing the spread of SARS-CoV-2 and contributing to COVID-19 control.

Outbreaks of rhinofacial and rhinopharyngeal zygomycosis in sheep in Paraíba, northeastern Brazil

Two outbreaks of zigomycosis with rhinofacial and two other with rhinopharyngeal lesions involving fungi with filamentous coaenocytic hyphae characteristic of entomoph-thoramycetous fungi are reported in the state of Paraíba, northeastern Brazil. One outbreak of rhinofacial zygomycosis occurred during the rainy season affecting 5 sheep. Another outbreak of the clinical form affected one out of 40 sheep during the dry season. Common clinical signs of the rhinofacial infection were bilateral serosanguineous nasal discharge with swelling of nostrils, upper lip, and the skin of the face. At necropsy the nasal mucosa showed dark brownish ulcerated areas which extended from the mucocutaneous region to 10cm inside the nasal vestibule. The mucosa of the hard palate was also ulcerated. The cutting surface of nostrils and palate showed a brownish or red spongeous tissue of friable consistency. One outbreak of rhinopharyngitis took place on an irrigated coconut farm; 7 out of 60 adult sheep were affected. Another outbreak affected a sheep in a flock of 80 during the dry season. Clinical signs as noisy respiration and dyspnoea due to mechanical blockage of the nasal cavities, swelling of the nostrils, and serosanguineous nasal discharge were observed. Six out of 8 sheep in this group showed exophthalmia, keratitis and unilateral corneal ulceration of the eye. The sheep either died of their infection or were euthanized after a clinical course of 7-30 days. At necropsy there was a dense yellow exudate in the nasopharyngeal area affecting the ethmoidal region, turbinate bones, paranasal sinuses, hard and soft palates, orbital cavity, pharynges, regional muscles and lymph nodes. Histopathologically both forms of the disease showed multifocal granulomas with an eosinophilic necrotic reaction (Splendore-Hoeppli phenomenon) containing ribbon-type coenocytic hyphae with 7-30mm in diameter similar to hyphae of zygomycetous fungi, possibly Conidiobolus spp. Outbrea...

Dois surtos de lesões rinofaciais e dois de lesões rinofaríngeas causadas por fungos com hifas filamentosas, raramente septadas, semelhantes às dos fungos entomophthorales, são descritos no Estado da Paraíba. Um surto da forma rinofacial afetou 5 ovinos durante a estação chuvosa. Outro surto desta forma clínica afetou um ovino de um grupo de 40, durante a época seca. Os sinais clínicos da forma rinofacial foram de corrimento serosanguinolento bilateral, com aumento de volume das narinas, lábio superior, e pele da face. Na necropsia, a mucosa nasal apresentava áreas ulceradas de cor marrom escuro, que se estendiam desde a região muco-cutánea até 10cm dentro do vestíbulo nasal. A mucosa do palato duro estava, também, ulcerada. A superfície de corte das narinas e palato apresentava-se marrom ou avermelhada de aspecto esponjoso e friável. Um surto de rinofaringite micótica ocorreu em uma plantação de coco irrigado, afetando 7 ovinos de um rebanho de 60 ovinos adultos. Outro surto desta forma da enfermidade afetou um único animal de um rebanho de 80, durante a época seca. Os animais apresentavam dispnéia, com respiração ruidosa devida ao bloqueio parcial das narinas, e corrimento nasal serosanguinolento. Seis dos oito animais afetados por esta forma da enfermidade apresentaram, em um olho, exoftalmia, ceratite e ulceração da córnea. Todos os ovinos morreram ou foram sacrificados após um curso clínico de 7-30 dias. Na necropsia exsudato amarelo consistente foi observado na região etmoidal, ossos turbinados, seios paranasais, palatos duro e mole, órbita, faringe, e músculos e linfonodos regionais. No estudo histológico, ambas as formas da doença mostraram granulomas multifocais com áreas necróticas eosinofílicas (material de Splendore-Hoeppli) contendo hifas com 7-30mm de diâmetro, raramente septadas, semelhantes às dos fungos entomophthorales, possivelmente Conidiobolus spp. Surtos de ambas as formas de rinite micótica são freqüentes na região ...