Background The current standard for COVID-19 diagnosis, RT-qPCR, has important drawbacks for its use as a tool for epidemiological control, including the need of laboratory-processing, high cost, and long turnaround from sampling to results release. Antigen-based rapid diagnostic tests (Ag-RDT) provide a promising alternative for this purpose. Methods We assessed the analytical and clinical performance of the Ag-RDT Panbio COVID-19 Ag Test (Abbott), using RT-qPCR as a reference test. The clinical performance was assessed using nasopharyngeal swabs, collected in routine practice for case confirmation and contact tracing, and nasal mid-turbinate swabs, collected in preventive screenings of asymptomatic individuals. Fresh samples were analysed by RT-q-PCR, stored at -80 C, and analysed using the Ag-RDT according to the manufacturer instructions. Findings The Ag-RDT had a limit of detection of 6.5 *105 copies/reaction. The clinical performance was assessed on 1,406 frozen swabs with a PCR result available: 951 (67.7%) positive and 455 (32.4%) negative. The Ag-RDT identified the presence of SARS-CoV-2 in 872 of 951 PCR-positive samples (91.7%; 95% CI 89.8-93.4 and ruled out its presence in 450 of 455 PCR-negative samples (specificity 98.9%; 95% CI 97.5 - 99.6). Sensitivity increased in samples with lower Ct values (Ct <25, 98.2%; Ct<30, 94.9%) and was higher among symptomatic cases (92.6%) and their contacts (94.2%) than among asymptomatic individuals (79.5%). In the setting of asymptomatic screening, sensitivity also increased with lower Ct values (Ct <25, 100%; Ct<30, 98.6%). Assuming a pre-test probability of 5%, the negative and positive predictive values were 99.6% (99.5 - 99.6) and 81.5% (65.0 - 93.2), respectively. Interpretation The Panbio COVID-19 Ag-RDT has high sensitivity for detecting the presence of SARS-CoV-2 in nasal or nasopharyngeal swabs of both, symptomatic and asymptomatic individuals. The diagnostic performance of the test is particularly good in samples with viral loads associated with high risk of viral transmission (Ct <25), which show high positive and negative predictive values even when assuming a prevalence as low as 5%.

Analytical and clinical performance of the panbio COVID-19 antigen-detecting rapid diagnostic test Dear Editor, Recent articles in this Journal have suggested the potential of antigen-based rapid diagnostic tests (Ag-RDT) as low-cost and ease-of-use tools for massive screening and epidemiological surveillance of SARS-CoV-2 spread. 1 , 2 Based on a pre-screening of four Ag-RDT on 40 frozen specimens from nasopharyngeal swabs with known PCR results (Table S1, Appendix), we selected the Panbio COVID-19 Ag Test (Abbott) for investigating its analytical and clinical performance. The analysis of serial dilutions of a SARS-CoV-2 isolate, propagated in Vero E6 cells, yielded a limit of detection (LoD) of 6.5 × 10 5 genome copies/reaction (Table S2). According to this value, the test would not detect SARS-CoV-2 infection in respiratory specimens with very low viral load. Still, the LoD was one logarithmic unit below the 10 6 copies/mL threshold necessary for successful virus isolate from respiratory samples. 3 The clinical performance was analysed on frozen swabs from 1406 individuals (mean age 40.4 years; SD 24.5) with an RT-qPCR result available: 951 (67.6%) positive and 455 (32.4%) negative. Overall, 446 (31.7%) and 473 (33.6%) samples were nasopharyngeal swabs from symptomatic individuals and contacts exposed to symptomatic cases, respectively, and 487 (34.6%) were nasal mid-turbinate swabs from asymptomatic individuals collected in screening campaigns. The cycle threshold (Ct) of PCR-positive samples was

A molecular diagnostic technique based on real-time PCR was developed for the simultaneous detection of three of the most frequent causative agents of fungal opportunistic pneumonia in AIDS patients: Pneumocystis jirovecii, Histoplasma capsulatum, and Cryptococcus neoformans/Cryptococcus gattii. This technique was tested in cultured strains and in clinical samples from HIV-positive patients. The methodology used involved species-specific molecular beacon probes targeted to the internal transcribed spacer regions of the rDNA. An internal control was also included in each assay. The multiplex real-time PCR assay was tested in 24 clinical strains and 43 clinical samples from AIDS patients with proven fungal infection. The technique developed showed high reproducibility (r 2 of >0.98) and specificity (100%). For H. capsulatum and Cryptococcus spp., the detection limits of the method were 20 and 2 fg of genomic DNA/20 l reaction mixture, respectively, while for P. jirovecii the detection limit was 2.92 log 10 copies/20 l reaction mixture. The sensitivity in vitro was 100% for clinical strains and 90.7% for clinical samples. The assay was positive for 92.5% of the patients. For one of the patients with proven histoplasmosis, P. jirovecii was also detected in a bronchoalveolar lavage sample. No PCR inhibition was detected. This multiplex real-time PCR technique is fast, sensitive, and specific and may have clinical applications.

Background This study aimed to compare self-reported changes on lifestyle behaviors during two phases of the COVID-19 pandemic in Spain, and to evaluate clinical and sociodemographic factors associated with lifestyles. Methods Two cross-sectional web surveys were conducted during lockdown (April 15-May 15, 2020) and seven months later (November 16-December 16, 2020). Lifestyle behaviors were self-reported by a multidimensional scale (SMILE-C). Two separate samples of respondents were analyzed. A multivariate regression model was performed to evaluate the association of SMILE-C scores with demographic and clinical variables. Results The sample comprised, 3412 participants from the first survey (S1) and in the S1 and 3635 from the second (S2). SMILE-C score decreased across surveys ( p < 0.001). The rates of positive screenings for depression and anxiety were similar between the surveys, whereas those for alcohol abuse decreased ( p < 0.001). Most participants in S2 reported that their lifestyle had not changed compared to those before the pandemic. Variables independently associated with an unhealthier lifestyle were working as an essential worker, lower educational level, previous mental disease, worse self-rated health, totally/moderate changes on diet, sleep or social support, as well as positive screenings for alcohol abuse, anxiety and depression. Limitations The cross-sectional design and recruitment by non-probabilistic methods limit inferring causality and the external validity of the results. Conclusions Overall lifestyle worsened seven months after the lockdown in Spain. Several demographic and clinical factors were associated with lifestyle scores. The contribution of common mental disorders to unhealthier lifestyles should be considered in order to prevent the negative impact of the pandemic.

A case of protothecosis causing non-ambulatory paraparesis in a dog without clinical evidence of disseminated infection is described. A five-year-old female Labrador retriever was referred with a 10-day history of progressive non-ambulatory paraparesis and lumbar pain as the only physical and neurological abnormalities. Lumbar myelography revealed severe extradural spinal cord compression extending from L4 to L7 vertebrae, and a right hemilaminectomy was performed. Surgical findings included an adherent whitish hard ill-defined mass. Cytology and biopsy results disclosed the presence of algae enclosed in a matrix of chronic inflammatory infiltrate. Culture confirmed the presence of Prototheca species. Neurological improvement occurred within a month, and the dog received antifungal treatment without evidence of clinical disseminated disease for 6 months, but died after a generalised tonic-clonic seizure. Post-mortem examination revealed multiple foci of inflammatory granulomatous infiltrate and algae-like structures in the brain, lumbar intumescence and cauda equina. Prototheca zopfii was identified using molecular biology methods.