Seroprevalence and indexes of IgG antibodies for SARS-CoV-2 infection among People Living With HIV, tuberculosis patients and healthcare workers, in Salvador, Brazil

ABSTRACT Introduction: COVID-19 can trigger different clinical presentations in distinct population groups, some of which are considered at higher risk of SARS-CoV-2 infection. Little is known about the susceptibility of certain populations to the infection. Objectives: We aimed to determine the prevalence of COVID-19 among People Living With HIV/AIDS (PLWH) attending a tertiary public hospital in Salvador, Brazil, patients with active pulmonary tuberculosis and Hospital's Healthcare Workers (HCW), and to compare their SARS-CoV-2 antibody levels. Methods: In this observational study we included 2294 participants from June 9, 2020 to August 10, 2021. IgG SARS-CoV-2 antibodies from all participants (275 PLWH, 42 with active tuberculosis and 1977 healthcare workers) were measured. Prevalence of COVID-19 and antibodies indexes were compared across groups. Results: We detected a higher prevalence of COVID-19 in patients with active tuberculosis (42.9%) than in PLWH (22.5%) or HCW (11.7%). Previously vaccinated participants with a COVID-19 history had median higher IgG antibody indexes (8.2; IQR: 5.5-10) than those vaccinated who did not have COVID-19 until the time of this study (4.1; IQR: 1.6-6.2, p < 0.001). Conclusion: Prevalence of previous SARS-CoV-2 infection was higher among tuberculosis patients than that found in HCW and PLWH, but antibodies levels were similar across groups.

Validation of the GeneXpert Xpress SARS-CoV-2 PCR assay using saliva as biological specimen.

In the pandemic, rapid and accurate detection of SARS-CoV-2 is crucial in controlling the outbreak. Recent studies have shown a high detection rate using saliva/oral fluids as specimens for laboratory detection of the virus. We intended to evaluate the test performance of the Xpert Xpress SARS-CoV-2 cartridge assay in comparison to a conventional qRT-PCR testing, using saliva as biological specimen. Forty saliva samples from symptomatic participants were collected. Conventional qRT-PCR was performed for amplification of E and RdRp genes and the Xpert Xpress SARS-CoV-2 assay amplified E and N2 genes. In the conventional assay, the median cycle threshold value of the E gene was 34.9, and of the RdRp gene was 38.3. In the Xpert Xpress assay, the median cycle threshold value of the E gene was 29.7, and of the N2 gene was 31.6. These results can allow a broaden use of molecular tests for management of COVID-19 pandemic, especially in resources-limited settings.

Validation of the GeneXpert Xpress SARS-CoV-2 PCR assay using saliva as biological specimen

ABSTRACT In the pandemic, rapid and accurate detection of SARS-CoV-2 is crucial in controlling the outbreak. Recent studies have shown a high detection rate using saliva/oral fluids as specimens for laboratory detection of the virus. We intended to evaluate the test performance of the Xpert Xpress SARS-CoV-2 cartridge assay in comparison to a conventional qRT-PCR testing, using saliva as biological specimen. Forty saliva samples from symptomatic participants were collected. Conventional qRT-PCR was performed for amplification of E and RdRp genes and the Xpert Xpress SARS-CoV-2 assay amplified E and N2 genes. In the conventional assay, the median cycle threshold value of the E gene was 34.9, and of the RdRp gene was 38.3. In the Xpert Xpress assay, the median cycle threshold value of the E gene was 29.7, and of the N2 gene was 31.6. These results can allow a broaden use of molecular tests for management of COVID-19 pandemic, especially in resources-limited settings.

Saliva is a reliable, non-invasive specimen for SARS-CoV-2 detection.

BACKGROUND: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the cause of Coronavirus Disease 2019 (COVID-19). Although Real Time Reverse Transcription Polymerase Chain Reaction (qRT-PCR) of respiratory specimens is the gold standard test for detection of SARS-CoV-2 infection, collecting nasopharyngeal swabs causes discomfort to patients and may represent considerable risk for healthcare workers. The use of saliva as a diagnostic sample has several advantages. OBJECTIVES: The aim of this study was to validate the use of saliva as a biological sample for diagnosis of COVID-19. METHODS: This study was conducted at Infectious Diseases Research Laboratory (LAPI), in Salvador, Brazil. Participants presenting with signs/symptoms suggesting SARS-CoV-2 infection underwent a nasopharyngeal swab (NPS) and/or oropharyngeal swab (OPS), and saliva collection. Saliva samples were diluted in PBS, followed by RNA isolation and RT-Real Time PCR for SARS-CoV-2. Results of conventional vs saliva samples testing were compared. Statistical analyses were performed using Statistical Package for the Social Sciences software (SPSS) version 18.0. RESULTS: One hundred fifty-five participants were recruited and samples pairs of NPS/OPS and saliva were collected. The sensitivity and specificity of RT-PCR using saliva samples were 94.4% (95% CI 86.4-97.8) and 97.62% (95% CI 91.7-99.3), respectively. There was an overall high agreement (96.1%) between the two tests. CONCLUSIONS: Use of self-collected saliva samples is an easy, convenient, and low-cost alternative to conventional NP swab-based molecular tests. These results may allow a broader use of molecular tests for management of COVID19 pandemic, especially in resources-limited settings.