Validation of a One-Step Reverse Transcription-Droplet Digital PCR (RT-ddPCR) Approach to Detect and Quantify SARS-CoV-2 RNA in Nasopharyngeal Swabs

Background. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has rapidly spread worldwide from the beginning of 2020. Quantitative reverse transcription-PCR (RT-qPCR) is, to this day, the preferred methodology for viral RNA detection, even if not without problems. To overcome some of the limitations still existing for the detection and quantification of nucleic acids in various applications, the use of one-step reverse transcription-droplet digital PCR (RT-ddPCR) has been established. The purpose of this study was, then, to evaluate the efficacy of ddPCR for the detection of SARS-CoV-2 RNA in nasopharyngeal swabs, optimizing the detection of low-viral load-burdened samples. Methods. The RT-ddPCR workflow was validated for sensitivity, specificity, linearity, reproducibility, and precision using samples from 90 COVID-19-infected patients referred to the Department of Laboratory Medicine of the University Hospital of Udine (Italy). Results. The present study shows that RT-ddPCR allows the detection of as low as 10.3 copies of a SARS-COV-2 E-gene per sample with a higher level of accuracy and precision, especially at low concentration. Conclusion. During the postpeak phase of the SARS-CoV-2 pandemic, it is essential to rely on a highly robust molecular biology method to identify infected subjects, whether they have symptoms or not, in order to prepare appropriate containment measures

SARS-CoV-2 transmission by asymptomatic healthcare workers positive to screening swab: an Italian study

Background SARS-CoV-2 spreads primarily through respiratory droplets of symptomatic individuals. With respect to asymptomatic individuals, there are conflicting results in the literature and a lack of studies specifically examining transmission in healthcare settings. Methods The aim of this retrospective study, conducted in a northeastern Italian region, was to estimate the contagiousness of asymptomatic healthcare workers (HCWs) who tested positive for SARS-CoV-2. Asymptomatic HCWs who tested positive for SARS-CoV-2 by real-time reverse transcription polymerase chain reaction (rRT-PCR) at a regular screening nasopharyngeal or oropharyngeal swab between 1 February 2020 and 15 September 2020 were considered index cases. Contacts who were at high risk of infection and had follow-up swabs were included. Contacts were considered infected if they had a positive follow-up swab and/or symptoms associated with COVID-19 confirmed by a positive test within 14 days of exposure. Information was taken from records previously collected to identify contacts. Infectivity was estimated using the attack rate (AR) with a 95% confidence interval (95% CI). Results Thirty-eight asymptomatic HCWs who were positive at the screening swab and 778 contacts were identified. Contacts included 63.8% of colleagues, 25.6% of patients, 7.7% of family members and 3.0% of other contacts. Seven contacts tested positive for SARS-CoV-2 (AR: 0.91%, 95% CI: 0.89-0.93). Five of them were family members (AR: 8.3%), one was a colleague (0.2%) and one was a contact of other type (4.2%). Conclusions Viral spread by asymptomatic HCWs was less than in other settings. Identification of risk factors for transmission and reliable indicators of infectivity would be important to prioritize preventive measures

The Fall in Antibody Response to SARS-CoV-2: a Longitudinal Study of Asymptomatic to Critically Ill Patients Up to 10 Months after Recovery

The aim of this study was to assess the long-term dynamics and factors associated with the serological response against the severe acute respiratory syndrome coronavirus 2 after primary infection. A prospective longitudinal study was conducted with monthly serological follow-up during the first 4 months, and then at 6, 8, and 10 months after the disease onset of all recovered adult in- and outpatients with coronavirus disease 2019 (COVID-19) attending Udine Hospital (Italy) during the first wave (from March to May 2020). A total of 546 individuals were included (289 female, mean age 53.1 years), mostly with mild COVID-19 (370, 68.3%). Patients were followed for a median of 302 days (interquartile range, 186 to 311). The overall seroconversion rate within 2 months was 32% for IgM and 90% for IgG. Seroreversion was observed in 90% of patients for IgM at 4 months and in 47% for IgG at 10 months. Older age, number of symptoms at acute onset, and severity of acute COVID-19 were all independent predictors of long-term immunity both for IgM (beta, linear regression coefficient, 1.10, P = 0.001; beta 5.15 P = 0.014; beta 43.84 P = 0.021, respectively) and for IgG (beta 1.43 P < 0.001; beta 10.46 P < 0.001; beta 46.79 P, 0.001, respectively), whereas the initial IgG peak was associated only with IgG duration (beta 1.12, P < 0.001). IgM antibodies disappeared at 4 months, and IgG antibodies declined in about half of patients 10 months after acute COVID-19. These effects varied depending on the intensity of the initial antibody response, age, and burden of acute COVID-19

Peer education for medical students on health promotion and clinical risk management

CONTEXT: Health promotion (HP) and clinical risk management (CRM) topics are seldom discussed during medical school lessons. Peer\u2010assisted learning (PAL) has long occurred informally in medical education, and interest in this method has recently grown, as it is considered a valuable technique for both tutors and tutees. AIMS: The aim was to evaluate the impact of HP and CRM PAL intervention on medical students\u2019 (tutees) knowledge level. SETTINGS AND DESIGN: A PAL intervention has been implemented at Udine University medical school during 2017. It was composed of lectures and practical activities conducted by ten near\u2010peer tutors. METHODS: The effectiveness has been evaluated by giving tutees: (1) a knowledge multiple\u2010choice questionnaire, before and after the intervention; (2) a satisfaction questionnaire; and evaluating (3) tutees\u2019 group assignments. STATISTICAL ANALYSIS USED: We performed descriptive analysis; then McNemar, Wilcoxon signed rank, Wilcoxon Mann\u2013Whitney, and t\u2010tests were applied. RESULTS: The number of students addressed by PAL intervention was 62. Difference in total correct answers among pre\u2010 and post\u2010intervention questionnaires showed a statistically significant improvement (P < 0.0001), both when analyzing it globally and by area (HP/CRM). Students\u2019 satisfaction for CRM was greater than for HP area (P = 0.0041). CONCLUSIONS: This educational intervention based on PAL showed its effectiveness producing a statistically significant improvement in students\u2019 knowledge. Our findings confirm that PAL could be a feasible method for HP and CRM topics