RESUMO
RESUMEN Introducción: Los medios de colecta de muestras clínicas con capacidad de desnaturalizar virus reducen los riesgos de contagio durante el transporte y procesamiento. Objetivo: Emplear el medio de transporte de ácidos nucleicos (TAN) en muestras de exudado nasofaríngeo colectadas para el diagnóstico de SARS-CoV-2. Métodos: Se realizó un estudio experimental para demostrar la capacidad del medio de inactivar la infectividad viral. Se tomó como modelo de virus envuelto el virus Zika (VZk), cuyo nivel de bioseguridad es 2. Se evaluó el desempeño clínico del medio TAN para el diagnóstico de SARS-CoV-2. Se empleó una cepa del VZk propagada en la línea celular Vero y, previo a la infección de las células, el VZk se puso en contacto a intervalos de tiempo diferentes (2; 15 y 30 min) con el medio TAN puro; y luego se realizaron diluciones seriadas (10-1-10-4). La inactivación viral se evaluó por RT-PCR, en el sobrenadante y células colectadas, al culminar el periodo de propagación. El desempeño clínico del medio TAN se estimó tomando como referencia el CITOSWAB® VTM, en 30 exudados nasofaríngeos colectados para diagnóstico de la infección por SARS-CoV-2. Resultados: El VZk preservó su infectividad a diluciones del inóculo ≥ 10-2, independientemente del tiempo de contacto. La sensibilidad y especificidad clínica del medio TAN para el diagnóstico de SARS-CoV-2 fueron del 100 %, respectivamente. Conclusiones: Los resultados sugieren que muestras clínicas positivas a VZk en diluciones ≤ 10-1 del medio TAN pueden ser manipuladas de forma segura, lo que pudiera aplicarse potencialmente al diagnóstico molecular del SARS-CoV-2.
ABSTRACT Introduction: Collection media of clinical samples with the capacity to denature viruses reduce the risk of contagion during transportation and processing. Objective: To use the nucleic acids transport media (NATM) in nasopharyngeal swab samples collected for the diagnosis of SARS-CoV-2. Methods: An experimental study was conducted to demonstrate the medium capacity to inactivate viral infectivity. Zika virus (ZIKV), of biosafety level 2, was used as an enveloped virus model. The clinical performance of the NATM for the diagnosis of SARS-CoV-2 was evaluated. A ZIKV strain propagated in the Vero cell line was used and, prior to cells infection, ZIKV was in contact at different intervals (2; 15, and 30 min) with pure NATM; subsequently, serial dilutions (10-1-10-4) were performed. Viral inactivation was evaluated by RT-PCR in the supernatant and the collected cells when the propagation period was completed. CITOSWAB® VTM was used as reference to estimate the clinical performance of the NATM in 30 nasopharyngeal swabs collected for the diagnosis of SARS-CoV-2 infection. Results: ZIKV remained infectious at inoculum dilutions of ≥ 10-2, regardless of contact time. Clinical specificity and sensitivity of the NATM for the diagnosis of SARS-CoV-2 were 100%, respectively. Conclusions: Results suggest that ZIKV positive clinical samples at dilutions ≤ 10-1 of the NATM can be safely handled, which could potentially be applied to the molecular diagnosis of SARS-CoV-2.
Assuntos
HumanosRESUMO
One of the challenges for control and prevention of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is the early diagnostic at the point of care. Several tests based on qualitative antigen detection have been developed; one of these is Elecsys SARS-CoV-2 Antigen immunoassay (Roche Diagnostics). In total, 523 nasopharyngeal swabs were randomly selected with the aims to evaluate sensitivity, specificity, cross-reactivity, positive and negative predictive value (PPV, NPV), and agreement of Elecsys SARS-CoV-2 Antigen immunoassay using reverse transcription-polymerase chain reaction (RT-PCR) STAT-NAT® coronavirus disease-2019 as reference test. Cross-reactivity was estimated using samples positive by RT-PCR to other respiratory viruses (influenza virus, parainfluenza virus, rhinovirus, coronavirus OC43, and HKU1). The overall sensitivity of Elecsys SARS-CoV-2 Antigen was 89.72% (288/321); specificity was 90.59% (183/202); and cross-reactivity to other respiratory viruses were not detected. Elecsys SARS-CoV-2 Antigen immunoassay showed a high sensitivity in samples with cycle threshold value <30, which ranged from 92.81% to 95.40%, independently of symptoms. PPV and NPV were 93.81% and 84.72%, respectively. The κ coefficient was 0.79 (95% confidence interval: 0.73-0.84), showing substantial agreement between both tests. The results suggest Elecsys SARS-CoV-2 Antigen immunoassay could be used as an alternative to RT-PCR testing, or in complement with it, to identify infectious individuals and reduce SARS-CoV-2 transmission.
