scholarly journals Estimating the effectiveness of routine asymptomatic PCR testing at different frequencies for the detection of SARS-CoV-2 infections

BMC Medicine ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Joel Hellewell ◽  
◽  
Timothy W. Russell ◽  
Rupert Beale ◽  
Gavin Kelly ◽  
...  
Keyword(s):  
Vulnerable Populations ◽  
Asymptomatic Infection ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Symptomatic Infection ◽  
Testing Frequency ◽  
Care Workers ◽  
Peak Sensitivity ◽  
Pcr Test ◽  
Over Time

Abstract Background Routine asymptomatic testing using RT-PCR of people who interact with vulnerable populations, such as medical staff in hospitals or care workers in care homes, has been employed to help prevent outbreaks among vulnerable populations. Although the peak sensitivity of RT-PCR can be high, the probability of detecting an infection will vary throughout the course of an infection. The effectiveness of routine asymptomatic testing will therefore depend on testing frequency and how PCR detection varies over time. Methods We fitted a Bayesian statistical model to a dataset of twice weekly PCR tests of UK healthcare workers performed by self-administered nasopharyngeal swab, regardless of symptoms. We jointly estimated times of infection and the probability of a positive PCR test over time following infection; we then compared asymptomatic testing strategies by calculating the probability that a symptomatic infection is detected before symptom onset and the probability that an asymptomatic infection is detected within 7 days of infection. Results We estimated that the probability that the PCR test detected infection peaked at 77% (54–88%) 4 days after infection, decreasing to 50% (38–65%) by 10 days after infection. Our results suggest a substantially higher probability of detecting infections 1–3 days after infection than previously published estimates. We estimated that testing every other day would detect 57% (33–76%) of symptomatic cases prior to onset and 94% (75–99%) of asymptomatic cases within 7 days if test results were returned within a day. Conclusions Our results suggest that routine asymptomatic testing can enable detection of a high proportion of infected individuals early in their infection, provided that the testing is frequent and the time from testing to notification of results is sufficiently fast.

scholarly journals Estimating the effectiveness of routine asymptomatic PCR testing at different frequencies for the detection of SARS-CoV-2 infections

2020 ◽  
Author(s):  
Joel Hellewell ◽  
Timothy W. Russell ◽  
Rupert Beale ◽  
Gavin Kelly ◽  
Catherine Houlihan ◽  
...  
Keyword(s):  
Vulnerable Populations ◽  
Research Unit ◽  
Asymptomatic Infection ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Symptomatic Infection ◽  
Testing Frequency ◽  
Peak Sensitivity ◽  
Pcr Test ◽  
Over Time

AbstractBackgroundRoutine asymptomatic testing using RT-PCR of people who interact with vulnerable populations, such as medical staff in hospitals or care workers in care homes, has been employed to help prevent outbreaks among vulnerable populations. Although the peak sensitivity of RT-PCR can be high, the probability of detecting an infection will vary throughout the course of an infection. The effectiveness of routine asymptomatic testing will therefore depend on testing frequency and how PCR detection varies over time.MethodsWe fitted a Bayesian statistical model to a dataset of twice weekly PCR tests of UK healthcare workers performed by self-administered nasopharyngeal swab, regardless of symptoms. We jointly estimated times of infection and the probability of a positive PCR test over time following infection, we then compared asymptomatic testing strategies by calculating the probability that a symptomatic infection is detected before symptom onset and the probability that an asymptomatic infection is detected within 7 days of infection.FindingsWe estimated that the probability that the PCR test detected infection peaked at 77% (54 - 88%) 4 days after infection, decreasing to 50% (38 - 65%) by 10 days after infection. Our results suggest a substantially higher probability of detecting infections 1–3 days after infection than previously published estimates. We estimated that testing every other day would detect 57% (33-76%) of symptomatic cases prior to onset and 94% (75-99%) of asymptomatic cases within 7 days if test results were returned within a day.InterpretationOur results suggest that routine asymptomatic testing can enable detection of a high proportion of infected individuals early in their infection, provided that the testing is frequent and the time from testing to notification of results is sufficiently fast.FundingWellcome Trust, National Institute for Health Research (NIHR) Health Protection Research Unit, Medical Research Council (UKRI)

scholarly journals Effectiveness of Preventive Measures in Keeping Low Prevalence of SARS-CoV-2 Infection in Health Care Workers in a Referral Children’s Hospital in Southern Italy

2021 ◽  
Vol 13 (1) ◽  
pp. 118-124
Author(s):  
Désirée Caselli ◽  
Daniela Loconsole ◽  
Rita Dario ◽  
Maria Chironna ◽  
Maurizio Aricò
Keyword(s):  
Health Care ◽  
Health Care Workers ◽  
Southern Italy ◽  
Hospital Setting ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Children's Hospital ◽  
Care Workers ◽  
Children’S Hospital ◽  
Second Wave

The coronavirus disease 2019 (COVID-19) pandemic now represents a major threat to public health. Health care workers (HCW) are exposed to biological risk. Little is currently known about the risk of HCW operating in pediatric wards for SARS-CoV-2 infection. The aim is to assess the prevalence of SARS-CoV-2 infection in HCW in a third-level children’s hospital in Southern Italy. An observational cohort study of all asymptomatic HCW (physician, technicians, nurses, and logistic and support operators) was conducted. HCW were screened, on a voluntary basis, for SARS-CoV-2 by RT-PCR on nasopharyngeal swab performed during the first wave of COVID-19. The study was then repeated, with the same modalities, at a 7-month interval, during the “second wave” of the COVID-19 pandemic. At the initial screening between 7 and 24 April 2020, 525 HCW were tested. None of them tested positive. At the repeated screening, conducted between 9 and 20 November 2020, 627 HCW were tested, including 61 additional ones resulting from COVID-emergency recruitment. At this second screening, eight subjects (1.3%) tested positive, thus being diagnosed as asymptomatic carriers of SARS-CoV-2. They were one physician, five nurses, and two HCW from the logistic/support services. They were employed in eight different wards/services. In all cases, the epidemiological investigation showed convincing evidence that the infection was acquired through social contacts. The study revealed a very low circulation of SARS-CoV-2 infection in HCW tested with RT-PCR. All the infections documented in the second wave of epidemic of SARS-CoV-2 were acquired outside of the workplace, confirming that in a pediatric hospital setting, HCW education, correct use of personal protective equipment, and separation of the COVID-patient pathway and staff flow may minimize the risk derived from occupational exposure.

scholarly journals The value of anal swab RT-PCR for COVID-19 diagnosis in adult Indonesian patients

2021 ◽  
Vol 8 (1) ◽  
pp. e000590
Author(s):  
Murdani Abdullah ◽  
Dedy Gunawanjati Sudrajat ◽  
Virly Nanda Muzellina ◽  
Juferdy Kurniawan ◽  
Aulia Rizka ◽  
...  
Keyword(s):  
Clinical Laboratory ◽  
Gastrointestinal Symptoms ◽  
High Specificity ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Severe Condition ◽  
Hospitalised Patients ◽  
Anal Swab ◽  
Low Sensitivity ◽  
Pcr Test

ObjectiveThis study will test the performance of the anal swab PCR test when compared with the nasopharyngeal swab PCR test as a diagnostic tool for COVID-19.DesignAn observational descriptive study which included hospitalised suspected, or probable cases of hopitalised COVID-19 patients, conducted in Dr. Cipto Mangunkusumo National Hospital, Ciputra Hospital, Mitra Keluarga Depok Hospital and Mitra Keluarga Kelapa Gading Hospital, Indonesia. Epidemiological, clinical, laboratory and radiology data were obtained. Nasopharyngeal and anal swabs specimens were collected for SARS-CoV-2 RNA detection.ResultsWe analysed 136 subjects as part of this study. The clinical spectrum of COVID-19 manifesation in this study was typical of hospitalised patients, with 25% classified as mild cases, 14.7% in severe condition and 12.5% of subjects classified as having acute respiratory distress syndrome. When compared with nasopharyngeal swab as the standard specimen for reverse transcription polymerase chain reaction (RT-PCR) detection of SARS-CoV-2 antigen, the sensitivity and specificity of the anal swab was 36.7% and 93.8%, respectively. The positive and negative predictive value were 97.8% and 16.5 %, respectively. The performance of the anal swab remained similar when only the subgroup of patients with gastrointestinal symptoms (n=92, 67.6%) was analysed (sensitivity 40% and specificity 91.7%). Out of all the subjects included in analysis, 67.6% had gastrointestinal symptoms. Similarly, 73.3% of patients in the anal swab-positive group had gastrointestinal symptoms. The two most common gastrointestinal symptoms in the subjects’ population were nausea and anorexia.ConclusionAnal swab specimen has low sensitivity (36.7%) but high specificity (93.8%) for detecting SARS-CoV-2 antigen by RT-PCR. Only one additional positive result was found by anal swab among the nasopharyngeal swab-negative group. Anal swab may not be needed as an additional test at the beginning of a patient’s diagnostic investigation and nasopharyngeal swab RT-PCR remains as the standard diagnostic test for COVID-19.

COVID-19 Reinfection in a Healthcare Worker; Is There a Definitive Immunity Against SARS-CoV-2?

2021 ◽  
Author(s):  
Sayyed Reza Ahmadi ◽  
Saeideh Anvari Ardakani ◽  
Navid Kalani ◽  
Seyed Reza Habibzadeh ◽  
Elnaz Vafadar Moradi ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Healthcare Worker ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Chain Reaction ◽  
Case Presentation ◽  
Long Period ◽  
Polymerase Chain ◽  
Pcr Test ◽  
First Admission

Introduction: While our knowledge is limited about COVID-19 immunity, recent cases of reinfection have raised concerns. Case presentation: Here, we report a case of COVID-19 reinfection after three months from recovery in a healthcare worker with negative IgM and IgG at the second infection and positive nasopharyngeal swab Reverse transcription polymerase chain reaction (RT-PCR) test despite being discharged with two negative RT-PCR tests at the first admission. Symptoms at first admission were fever, headache, sore throat, diarrhea, and vomiting and got changed to myalgia and anosmia. Conclusion: The strength of this case report is the long period (three months) between the infection and reinfection while other cases reported in literature were reinfected less than one month after their first infection.

scholarly journals Conjunctivitis as sole symptom of COVID-19: A case report and review of literature

2020 ◽  
pp. 112067212094628 ◽  
Author(s):  
Zeynep Kayaarasi Ozturker
Keyword(s):  
Health Care ◽  
Case Report ◽  
Blood Analysis ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Care Workers ◽  
Atypical Manifestations ◽  
Novel Virus ◽  
The Right ◽  
Care Worker

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel virus causing an ongoing pandemic in 2020. Although the symptomatic patients infected by SARS-CoV-2 generally show respiratory distress, atypical manifestations such as conjunctivitis are also observed. A series of cases are reported in which reverse transcriptase polymerase chain reaction (RT-PCR) testing on tears had demonstrated the presence of the virus. However, the transmission of the virus through ocular fluids remains unknown. Case description: In this case report, the development of conjunctivitis is presented as the sole symptom of a new coronavirus disease 2019 (COVID-19) in an emergency health care worker. The patient’s first application was to the ophthalmology clinic due to redness, stinging, tearing, and photophobia for one day in the right eye. The patient had no symptoms of fever, cough, shortness of breath, or fatigue. Two days later, the RT-PCR test, blood analysis, and chest computed tomography (CT) were applied to the patient for being in contact with a COVID positive patient. Conjunctival swabs did not identify SARS-CoV-2 by RT-PCR. However, nasopharyngeal swab and blood test confirmed the diagnosis of COVID-19. Chest CT did not show pneumonia. Conclusion: This phenomenon shows that conjunctivitis may occur as a sole manifestation of COVID-19 which needs to be carefully evaluated by health care workers and eye care professionals during the pandemic.

scholarly journals SARS-CoV-2 Detection in Fecal Sample from a Patient with Typical Findings of COVID-19 Pneumonia on CT but Negative to Multiple SARS-CoV-2 RT-PCR Tests on Oropharyngeal and Nasopharyngeal Swab Samples

Medicina ◽  
2021 ◽  
Vol 57 (3) ◽  
pp. 290
Author(s):  
Barbara Brogna ◽  
Carlo Brogna ◽  
Mauro Petrillo ◽  
Adriana Modestina Conte ◽  
Giulio Benincasa ◽  
...  
Keyword(s):  
Respiratory Tract ◽  
Clinical Symptoms ◽  
Nasopharyngeal Swab ◽  
Upper Respiratory Tract ◽  
Rt Pcr ◽  
Chain Reaction ◽  
Negative Results ◽  
Upper Respiratory ◽  
Polymerase Chain ◽  
Pcr Test

Reverse transcriptase polymerase chain reaction (RT-PCR) negative results in the upper respiratory tract represent a major concern for the clinical management of coronavirus disease 2019 (COVID-19) patients. Herein, we report the case of a 43-years-old man with a strong clinical suspicion of COVID-19, who resulted in being negative to multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RT-PCR tests performed on different oropharyngeal and nasopharyngeal swabs, despite serology having confirmed the presence of SARS-CoV-2 IgM. The patient underwent a chest computed tomography (CT) that showed typical imaging findings of COVID-19 pneumonia. The presence of viral SARS-CoV-2 was confirmed only by performing a SARS-CoV-2 RT-PCR test on stool. Performing of SARS-CoV-2 RT-PCR test on fecal samples can be a rapid and useful approach to confirm COVID-19 diagnosis in cases where there is an apparent discrepancy between COVID-19 clinical symptoms coupled with chest CT and SARS-CoV-2 RT-PCR tests’ results on samples from the upper respiratory tract.

scholarly journals Comparison of SARS‐CoV‐2 detection from nasopharyngeal swab samples by the Roche cobas 6800 SARS‐CoV‐2 test and a laboratory‐developed real‐time RT‐PCR test

2020 ◽  
Vol 92 (9) ◽  
pp. 1695-1698 ◽  
Author(s):  
Elisabet Pujadas ◽  
Nnaemeka Ibeh ◽  
Matthew M. Hernandez ◽  
Aneta Waluszko ◽  
Tatyana Sidorenko ◽  
...  
Keyword(s):  
Real Time ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Pcr Test ◽  
Roche Cobas

scholarly journals Covid 19 and orthopaedic surgery in a large trauma centre in India

2020 ◽  
Author(s):  
Kannan Karuppiah Kumar ◽  
Thomas Chandy ◽  
M N Kumar ◽  
Muniramaiah Ravishankar ◽  
Krishan Prasad ◽  
...  
Keyword(s):  
Emergency Surgery ◽  
Orthopaedic Surgery ◽  
Tertiary Care ◽  
Trauma Centre ◽  
High Rate ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Orthopaedic Patients ◽  
Positive Rate ◽  
Pcr Test

Background - We are in the midst of a pandemic caused by the novel SARS-Cov-2 virus. A large percentage of the patients are asymptomatic and hospitals around the world are struggling to restart routine services. We report the results of a universal testing protocol of all patients who underwent orthopaedic surgery in the month of July 2020 in a large orthopaedic speciality hospital in Bangalore, India. Methods - A retrospective study of all patients who underwent orthopaedic surgery in the month of July 2020 at a tertiary care orthopaedic speciality hospital in Bangalore, India. All patients underwent nasopharyngeal swab test before surgery. A questionnaire was used to assess the patient before the RT-PCR nasopharyngeal swab test. Data regarding imaging, investigations and follow up was recorded. Results - In the month of July 2020, 168 patients underwent routine nasopharyngeal RT -PCR swab test for COVID - 19 prior to planned orthopaedic surgical procedure (Both trauma and elective cases). 16 of the RT-PCR tests were positive. However vascular cases and absolute emergencies were done without a RT -PCR test with PPE and all universal precautions. 11 patients underwent emergency surgery without a RT-PCR test. All 16 cases who were positive were asymptomatic. The asymptomatic positive rate was 9.52%. Of the 11 patients who underwent emergency surgery without a RT-PCR test, only one patient had a positive test post - operatively. Conclusions - Routine nasopharyngeal RT-PCR testing revealed a high rate of asymptomatic cases. If the RT-PCR test is positive, it is best to defer the case till the test returns negative. All precautions must be taken while performing emergency surgeries. Our algorithm in managing patients has proven to be effective and can be replicated with ease to continue operating and taking care of orthopaedic patients during this pandemic.

scholarly journals What are the Clinical Implications of a Positive RT-PCR Test 6 Months after a Mild SARS-CoV-2 Infection?

2021 ◽  
Author(s):  
Joao Gabriel De Carvalho ◽  
Kateryna Hvozdara
Keyword(s):  
Surgical Treatment ◽  
Hip Fracture ◽  
Respiratory Symptoms ◽  
Nasopharyngeal Swab ◽  
Clinical Implications ◽  
Rt Pcr ◽  
Testing Methods ◽  
Viral Shedding ◽  
Pcr Test

We present the case of an 84-year-old female patient hospitalized for surgical treatment of a hip fracture who re-tested positive for SARS-CoV-2 with an RT-PCR nasopharyngeal swab approximately 6 months after presenting mild respiratory symptoms with confirmed COVID-19 in April 2020. We discuss the possibility of reinfection, long-term viral shedding and residual positivity, the limitations of RT-PCR swab tests, and the necessity for new testing methods as the COVID-19 pandemic spreads and long-lasting immunity is uncertain.

scholarly journals Impact of Full Vaccination with mRNA BNT162b2 on SARS-CoV-2 Infection: Genomic and Subgenomic Viral RNAs Detection in Nasopharyngeal Swab and Saliva of Health Care Workers

2021 ◽  
Vol 9 (8) ◽  
pp. 1738
Author(s):  
Michela Deiana ◽  
Antonio Mori ◽  
Chiara Piubelli ◽  
Francesca Perandin ◽  
Davide Treggiari ◽  
...  
Keyword(s):  
Health Care ◽  
Real Time ◽  
Health Care Workers ◽  
Low Frequency ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Subgenomic Rna ◽  
Viral Rnas ◽  
Social Settings ◽  
Care Workers

SARS-CoV-2 infection was monitored in 1898 health care workers (HCWs) after receiving full vaccination with BNT162b2. Untill 30 June 2021, 10 HCWs tested positive for SARS-CoV-2 using real time RT-PCR, resulting in a 4-month cumulative incidence of 0.005%. The infection was mildly symptomatic in six (60%) and asymptomatic in four (40%) individuals. Among the infected HCWs, eight consenting individuals provided paired NPS and saliva during the course of infection, for the purpose of the analysis performed in the present study. Genomic and subgenomic viral RNAs were investigated using real-time RT-PCR in both biological specimens. The temporal profile of viral load was measured using ddPCR. Viral mutations were also analysed. Subgenomic viral RNA was detected in 8/8 (100%) NPS and in 6/8 (75%) saliva specimens at the baseline. The expression of subgenomic RNA was observed for up to 7 days in 3/8 (38%) symptomatic cases. Moreover, concordance was observed between NPS and saliva in the detection of viral mutations, and both N501Y and 69/70del (associated with the B.1.1.7 variant) were detected in the majority 6/8 (75%) of subjects, while the K417T mutation (associated with the P.1-type variants) was detected in 2/8 (25%) individuals. Overall, our findings report a low frequency of infected HCWs after full vaccination. It is, therefore, important to monitor the vaccinees in order to identify asymptomatic infected individuals. Saliva can be a surrogate for SARS-CoV-2 surveillance, particularly in social settings such as hospitals.

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