Molecular point-of-care tests: efficiency of RT-LAMP in the rapid diagnosis of COVID-19 to assess hospital access.

Background: Safe hospital access needs rapid testing for SARS-CoV-2 to enable rationale use of limited resources. The current standard method for Coronavirus detection is the RT-qPCR. This study aimed to determine the diagnostic performance of the new rapid RT-LAMP test, compared to RT-qPCR, and his efficiency for rapid hospital access through the Emergency Department (E.D.). Method(s): 1576 UTM nasopharyngeal swabs, collected in E.D., have been tested for SARS-CoV-2 infection, using a kit RTLAMP. The same samples were also analyzed with a traditional RT-qPCR assay and the results have been compared in terms of sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). Result(s): The assay has demonstrated a sensitivity of 73.3% (95%CI: 62.4/82.0) and specificity of 87.1% (95%CI: 85.3/88.7), PPV 22.1%, NPV 98.5%. Conclusion(s): ICGENE RNA RT-LAMP kit (ICGENEHEALTH;Enbiotech, Angri, Salerno, Italy) efficiently exclude the presence of infection and reliably detects infectious patients (with Ct<30). RNA RT-LAMP could replace rRTPCR where there is the need to rapidly identify potentially contagious individuals, but its low PPV suggests that positive results should be confirmed by a reference method.Copyright © 2022 EDIZIONI MINERVA MEDICA.

Efficiency of rapid POC antigen in frontline screening for SARS-CoV-2 infection at emergency department admissionc

Background: In the emergency department (ED) setting, rapid testing for SARS-CoV-2 enables early but rationale use of limited isolation resources. The use of Antigen Point Of Care tests (POC Antigen) might be an essential tool especially for the Turn Arround Time of response, but it is necessary to clarify whether POC Antigen can be used safely specially for 'rule-out' (valid negative testing). Methods: Since September 2020, we have implemented POC antigen evaluation in nasopharyngeal (dNP) dry swab (SD Biosensor Standard F COVID-19 Ag FIA) in the first level evaluation path of the patient at ED admission. In each suspected or not suspected COVID-19 patient two sequential dNP swabs were obtained for RTPCR viral tests and for POC Antigen. All the results were retrospectively assessed for the performance, in comparison to the RT-PCR (Cepheid Xpert Xpress SARSCoV-2 and Altona RealStar® SARS-CoV-2 RT-PCR), in terms of sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). Results: We included n = 3645 patients from the ED. The sensitivity of the POC Antigen was 73.0 (95%CI: 66.6/78.5)% and the specificity was 97.2 (95%CI: 96.6/97.7)% with a SARSCoV-2 prevalence of 5.8%;the PPV was 61.8 (95%CI: 55.7/67.7)% and NPV 98.3 (95%CI: 97.8/98.7)%. Thus, n = 57 patients showed false negative POC Antigen results and n = 85 false positive POC Antigen. All positive POC Antigen were quickly confirmed. All the false negative POC Antigen results were tested with high productivity tool. The performance of the POC Antigen was compared with a cut-off threshold cycle (Ct) value of RT-PCR. In patients with Ct values η32, the sensitivity was 79.8 (95%CI: 73.6/84.8)% and the (NPV) 98.8 (95%CI: 98.4/99.2)%. In patients with Ct values η28, the sensitivity was 88.5 (95%CI: 82.9/92.4)% and the (NPV) 99.4 (95%CI: 99.1/99.6)%. In patients with Ct values η25, the sensitivity was 98.1 (95%CI: 94.5/99.3)% and the (NPV) 99.9 (95%CI: 99.7/100)%. Conclusions: We conclude that the use of POC Antigen allowed a rapid classification and an early identification of COVID-19 Infection. In asymptomatic patients, the use of the antigen ensured a low risk of transmission of the infection, being rarely associated to low CT values, index of high viral load.