A comparative study of isothermal nucleic acid amplification methods for SARS-CoV-2 detection at point-of-care

COVID-19, caused by the novel coronavirus SARS-CoV-2, has put most of the world under lockdown. Despite approved vaccines, COVID-19 cases, hospitalizations, and deaths have remained on the rise. Rapid diagnosis and necessary public health measures are still key parts to contain the pandemic. Here, the colorimetric isothermal nucleic acid amplification tests (iNAATs) for SARS-CoV-2 detection based on loop-mediated isothermal amplification (LAMP), cross-priming amplification (CPA), and polymerase spiral reaction (PSR) were designed and compared in performance for the first time. The findings showed that, for the detection of SARS-CoV-2 genomic-RNA, LAMP outperformed both CPA and PSR, reaction mix exhibiting the limit of detection (LOD) of roughly 43.14 copies/reaction. The results can be read with the naked eye within 45 minutes, without cross-reactivity to closely related coronaviruses. The direct detection of SARS-CoV-2 RNA in simulated specimens by iNAATs was also successful. Additionally, the lyophilized reagents for LAMP reactions maintained the sensitivity and LOD of the liquid assays. The colorimetric LAMP assay was validated using clinical samples, showing 98.1% sensitivity and 100% specificity upon using extracted samples and 82.4% sensitivity and 86.2% specificity upon using unextracted specimens. The results indicate that the direct colorimetric LAMP assay developed is highly suitable for detecting SARS-CoV-2 at point-of-care.

Evaluation of reverse transcriptase-polymerase spiral reaction assay for rapid and sensitive detection of severe acute respiratory syndrome coronavirus 2.

BACKGROUND AND AIM: Existing real-time reverse transcriptase PCR (RT-qPCR) has certain limitations for the point-of-care detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) since it requires sophisticated instruments, reagents and skilled laboratory personnel. In this study, we evaluated an assay termed the reverse transcriptase-polymerase spiral reaction (RT-PSR) for rapid and visual detection of SARS-CoV-2. METHODS: The RT-PSR assay was optimized using RdRp gene and evaluated for the detection of SARS-CoV-2. The time of 60min and a temperature of 63°C was optimized for targeting the RNA-dependent RNA polymerase gene of SARS-CoV-2. The sensitivity of the assay was evaluated by diluting the in-vitro transcribed RNA, which amplifies as low as ten copies. RESULTS: The specific primers designed for this assay showed 100% specificity and did not react when tested with other lung infection-causing viruses and bacteria. The optimized assay was validated with 190 clinical samples in two phases, using automated RTPCR based TrueNat test, and the results were comparable. CONCLUSIONS: The RT-PSR assay can be considered for rapid and sensitive detection of SARS-CoV-2, particularly in resource-limited settings. To our knowledge, there is as yet no RT-PSR-based kit developed for SARS-CoV-2.

Psychosocial risks factors among victim support workers during the COVID-19 pandemic: a study with the Copenhagen Psychosocial Questionnaire.

BACKGROUND: Being a victim support worker (VSW) involves exposure to victims' suffering, pain, and traumatic events, which may trigger the risk of VSWs developing mental health problems. Psychosocial risks (PSR) and work-related stress are considered the most challenging issues in occupational safety and health, considering they impact individuals, organizations, and economies. METHODS: The purpose of the present study was to identify the PSR in a sample of 196 Portuguese victim support workers (VSW) (Mean age = 36.49; SD = 10.52). A questionnaire with socio-demographic characteristics, variables related to VSW's job, and the Portuguese medium version of the Copenhagen Psychosocial Questionnaire II (COPSOQ II) were used to assess these professionals' perception of PSR factors. RESULTS: The results reveal that although VSW recognizes some psychosocial factors favourable to their health and well-being, they also identify some PSR that place them at intermediate and severe risk, i.e., emotional and cognitive demands, which are the main areas of risk to the VSW. VSW over 38 years old scored higher in job insecurity, burnout, and offensive behaviours. CONCLUSIONS: These findings give important insights into the areas that must be enhanced in this context involving VSW. Additionally, the results highlight the relevance of encouraging a healthy and supportive work environment, preventing and promoting the health and well-being of VSW, particularly when considering the coronavirus disease (COVID-19) pandemic.

Search for fast radio transients using Arecibo drift-scan observations at 1.4 GHz

We conducted a drift-scan observation campaign using the 305-m Arecibo telescope in 2020 January and March when the observatory was temporarily closed during the intense earthquakes and the initial outbreak of the COVID-19 pandemic, respectively. The primary objective of the survey was to search for fast radio transients, including fast radio bursts (FRBs) and rotating radio transients (RRATs). We used the seven-beam ALFA receiver to observe different sections of the sky within the declination region similar to(10 degrees-20 degrees) on 23 nights and collected 160 h of data in total. We searched our data for single-pulse transients, of covering up to a maximum dispersion measure of 11 000 pc cm(-3) at which the dispersion delay across the entire bandwidth is equal to the 13-s transit length of our observations. The analysis produced more than 18 million candidates. Machine learning techniques sorted the radio frequency interference and possibly astrophysical candidates, allowing us to visually inspect and confirm the candidate transients. We found no evidence for new astrophysical transients in our data. We also searched for emission from repeated transient signals, but found no evidence for such sources. We detected single pulses from two known pulsars in our observations and their measured flux densities are consistent with the expected values. Based on our observations and sensitivity, we estimated the upper limit for the FRB rate to be <2.8 x 10(5) sky(-1) d(-1) above a fluence of 0.16 Jy ms at 1.4 GHz, which is consistent with the rates from other telescopes and surveys.