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Biochimica Clinica ; 45(SUPPL 2):S52, 2022.
Article in English | EMBASE | ID: covidwho-1733010


Background. One of the strategies suggested for the containment of SARS-CoV-2 pandemic is testing at risk populations with rapid turn-out of results, contact tracing and isolation of infected individuals, at least until vaccination programs have been completed. Molecular testing of naso-pharyngeal swabs (NPS) is considered gold-standard, but antigenic testing should offer the advantage of being more rapid. Aim. The aim of this study was to evaluate the clinical performance of two chemiluminescent immunoassays on laboratory automated platforms, LIAISON® SARS-CoV-2 Ag Assay (DiaSorin) and Elecsys SARS-CoV-2 Antigen (Roche), to detect SARS-CoV-2 N antigen in NPS. Patients and Methods. A total of 281 subjects were consecutively enrolled (116 M, 165 F) from three different cohorts: 14 were COVID-19 in-patients (Group 1), 149 were patients enrolled at the emergency unit (Group 2) while 118 were healthcare employees under SARS-CoV-2 periodic surveillance (Group 3). All subjects underwent NPS with eSwab Copan. Antigen and molecular testing were performed soon after collection. Results. Thirty subjects were SARS-CoV-2 positive at molecular testing. Liaison antigen was positive (>200 TCID50/ml) in 22/30 (Se=73.3%), equivocal (100-200 TCID50/ml) in 4/30 and negative (<100 TCID50/ml) in 4/30 subjects. Specificity was 61.8% since 60/157 negative samples had equivocal results. With Elecsys sensitivity was 75.9% and specificity 99.5%. ROC curves were performed to compare the two assays and to identify the best cut-off. The areas under the curves were not different (η2=0.14;Prob>η2=0.7077). The highest likelihood ratio for Liaison corresponded to 150 TCID50ml cut-off, while for Elecsys to 1 index value. With these thresholds sensitivity of these two assays were 86% and 87% respectively, with 99% specificity. The limitations in sensitivity were due to false negative results for samples with Ct values at molecular analysis higher than 25. No false negative case was recorded among those with Ct lower than 25. Conclusions. In conclusion NPS SARS-CoV-2 antigen testing with chemiluminescent immunoassays allows the rapid detection of positive samples with a sensitivity and specificity that meet the recommendations of the WHO for this type of testing.

Open Forum Infectious Diseases ; 7(SUPPL 1):S262-S263, 2020.
Article in English | EMBASE | ID: covidwho-1185754


Background: In Italy the pandemic of COVID-19 infection has placed an enormous burden on health authorities: contact precautions are required to avoid viral transmission and people should be subjected to standard infection control procedures. This is crucial in a country experiencing a high number of confirmed cases of COVID-19 infection in Europe and where multidrug-resistant Gram-negative bacteria (MDR-GN) are endemic.The aim of this study was to compare the prevalence of MDR-GN in surveillance rectal swabs (SRS) and in clinical samples (CS) in the period March 1,2020- April, 24 2020 with respect to the previous 2-month period and to the previous year. Methods: The first SRS and the first CS with a MDR-GN isolate detected from 01/01/2019 to 24/04/2020 were included. Analysis was made by comparing three different study periods in 2019 and 2020 (Jan-Dec 2019, Jan-Feb 2020, and Mar-Apr 2020), for medical department, surgical department and intensive care department. Results: Overall, 612 MDR-GN organisms were identified (399 SRS and 213 CS): carbapenemase-producing Klebsiella pneumoniae and Acinetobacter baumanii (CPAB) were the most frequently detected (Figure 1). We observed an increased relative frequency of patients with MDR-GN detected in CS respect to those found in SRS (32.7% vs 44.5% vs 70.6%, p=0.0005): 5/12 CS detected in the last period were isolated from the respiratory tract (Figure 2). Nine patients with COVID-19 pneumonia had MDR-GN. All but two patients had a previous negative SRS performed 4 days before (median value) and the median interval between COVID-19 positivity and MDR-GN positivity was 7 days.The six patients with CPAB isolation were all hospitalized in the same ward, with partially overlapping hospital stays during the study period. In 5 of them, CPAB was detected in the respiratory tract (Figure 3). Conclusion: The first detection of MDR-GN in CS and the nosocomial MDR-GN acquisition despite cohorting due to COVID-19 infection underline the need to reinforce infection control measures in a high prevalence country during COVID-19 pandemia. A correct antimicrobial policy urged because, according to published data, most patients with COVID-19 infection received antimicrobial therapy: furthermore MDR-GN infection could play a role in the negative outcome of these patients.