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1.
Biochimica Clinica ; 45(SUPPL 2):S52, 2022.
Article in English | EMBASE | ID: covidwho-1733010

ABSTRACT

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.

2.
Biochimica Clinica ; 44(SUPPL 2):S67, 2020.
Article in English | EMBASE | ID: covidwho-983996

ABSTRACT

Introduction. Saliva has been proposed as a valid alternative to naso-pharyngeal swabs for detecting viral SARS-CoV-2 RNA sequences. In addition salivary glands have been described as a potential SARSCoV-2 virus reservoir, thus supporting the search for antibodies in saliva. Furthermore, the non-invasive nature of saliva collection is conducive to self-collection, patients' compliance for repeated testing, and reduction of risk to operators, thus making saliva an eligible matrix in the SARS-CoV-2 diagnostic process. Aim. The aim of this study was to verify whether standardized and safe saliva collection is suitable for SARS-CoV-2 molecular detection and IgA class antibody measurement. Methods. A total of 49 COVID-19 patients hospitalized at the University-Hospital of Padova (Italy) and 326 subjects who underwent screening underwent naso-pharyngeal (NP) swab and saliva collection using Salivette®. Repeat blood collections were performed to evaluate hematological and coagulation parameters, biochemical markers of inflammation, and renal, liver, heart and pancreatic involvement in hospitalized patients. In all patients and subjects, saliva SARS-CoV-2 (gene E) rRT-PCR was undertaken in parallel with NP swabs. Salivary IgA and serum IgA, IgG, IgM were measured on samples from hospitalized patients. Results. NP swabs were SARSCoV-2 positive in 9/49 patients. The comparison with saliva testing was possible for 43/49 patients, 7 of whom shared positivity, and 35 negativity while in one, the saliva result, not NP-swab, was positive. Positive molecular testing results were significantly associated with disease duration (p=0.0049). All the 326 screened subjects were SARS-CoV-2 negative on both NP and saliva swabs. Among the 27 saliva samples tested for IgA, 18 were IgA positive. Salivary IgA positivity was significantly associated with pneumonia (p=0.002) and CRP values (p=0.0183), not with other clinical and molecular data, or with immunoglubulins in serum.Conclusions. The results reported in the present study demonstrate that a standardized and safe saliva collection method can be adopted to detect SARS-CoV-2 infection in alternative to NP-swabs. Preliminary data on salivary IgA also support the use of saliva in local adaptive immunity patient monitoring.

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