Real-life performance of a COVID-19 rapid antigen detection test targeting the SARS-CoV-2 nucleoprotein for diagnosis of COVID-19 due to the Omicron variant

ObjectivesIt has been suggested that rapid antigen detection assays (RADT) may perform suboptimally in terms of sensitivity for the diagnosis of SARS-CoV-2 Omicron variant infection. To address this issue, we conducted a prospective study in primary health centers to evaluate the clinical performance of the Panbio COVID-19 Ag Rapid Test Device in nasopharyngeal specimens (NP) carried out at the point of care. MethodsWe recruited 244 patients (median age, 40 years; range 2-96; 141 female) with clinical suspicion of COVID-19 (232 adults and 12 children). 228/244 patients had been fully vaccinated (two doses) with licensed COVID-19 vaccines prior to recruitment. Most patients (222/244) were SARS-CoV-2 naive prior to enrollment. Patients were tested by RT-PCR and RADT within 5 days since symptoms onset. Results126 patients (51.6%) tested positive by both RT-PCR and RADT, 90 patients (36.8%) returned negative results by both assays and 28 patients (11.4%) yielded discordant results (RT-PCR+/RADT-). No patients tested RT-PCR-/RADT+. Overall specificity and sensitivity of RADT was 100% (95% CI, 95.9-100%) and 81.8% (95% CI, 75-87.1%) respectively. The sensitivity of the assay increased from 79.6% (95% CI, 66.4-88.5) when considering specimens collected at days 0-1 after symptoms onset, to 86.4% (95% CI, 66.7-95.3) when grouping the specimens obtained on days 4-5. ConclusionThe Panbio COVID-19 Ag Rapid Test Device perform well ([≥]80% sensitivity) as a point-of-care test for early diagnosis of COVID-19 due to the Omicron variant in primary healthcare centers.

Evolution of SARS-CoV-2 immune responses in nursing home residents following full dose of the Comirnaty COVID-19 vaccine

ObjectivesThere is scarce information as to the durability of immune responses elicited by the Comirnaty(R) COVID-19 vaccine in nursing home residents. Here, we assessed SARS-CoV-2-Spike (S)-targeted antibody and functional T cell responses at around 6 months after complete vaccination. MethodsThe sample comprised 46 residents (34 females; age, 60-100 years), of whom 10 had COVID-19 prior to vaccination. Baseline (median of 17.5 days after vaccination) and follow-up (median, 195 days) plasma specimens were available for quantitation of SARS-CoV-2-S antibodies and enumeration of SARS-CoV-2-S-reactive IFN-{gamma} CD4+ and CD8+ T cells by flow cytometry. ResultsIn total, 44/45 participants had detectable SARS-CoV-2-S antibodies at follow-up. Overall, antibody levels were found to decrease (median, 4.8 fold). Antibodies waning was more frequent (P<0.001) in SARS-CoV-2 naive (29/35) than in recovered (1/10) residents. SARS-CoV-2-S IFN-{gamma} CD8+ T cells were detected in 33/46 and 24/46 at baseline and follow-up, respectively. The figures for CD4+ T cell counterparts were 12/46 and 30/46. Detectable SARS-CoV-2 IFN-{gamma} CD8+ and CD4+ T cell responses at follow-up were more common in recovered (8/10 and 7/10, respectively) than in naive residents (9/36 and 25/36, respectively). For those with detectable responses at both time points, SARS-CoV-2-S IFN-{gamma} CD8+ T cell frequencies decreased significantly (P=0.001) over time whereas the opposite (P=0.01) was observed in CD4+ T cells. ConclusionAlmost all residents displayed detectable SARS-CoV-2-S-reactive antibodies and T cell responses, respectively, by around 6 months after complete vaccination with Comirnaty(R) COVID-19 vaccine, albeit generally waning in magnitude over time.

B and T cell immune responses elicited by the BNT162b2 (Pfizer BioNTech) COVID-19 vaccine in nursing home residents

ObjectivesThe immunogenicity of the BNT162b2 COVID-19 vaccine is understudied in elderly people with comorbidities. We assessed SARS-CoV-2-S-targeted antibody and T cell responses following full vaccination in nursing home residents (NHR). MethodsWe recruited 60 NHR (44 female; median age, 87.5 years), of whom 10 had previously had COVID-19, and 18 healthy controls (15 female; median age, 48.5 years). Pre- and post-vaccination blood specimens were available for quantitation of total antibodies binding RBD and enumeration of SARS-CoV-2-S-reactive IFN-{gamma} CD4+ and CD8+ T cells by flow cytometry. ResultsThe seroconversion rate in presumably SARS-CoV-2 naive NHR (95.3%), either with or without comorbidities, was similar to controls (94.4%). A robust booster effect was documented in NHR with prior COVID-19. Plasma antibody levels were higher in convalescent NHR than in individuals across the other two groups. A large percentage of NHR had SARS-CoV-2 S-reactive IFN-{gamma} CD8+ and/or CD4+ T cells at baseline, in contrast to healthy controls. Either CD8+ and/or CD4+ T-cell responses were documented in all control subjects after vaccination. Contrariwise, the percentage of NHR exhibiting detectable SARS-CoV-2 IFN-{gamma} CD8+ or CD4+ T-cell responses (or both), irrespective of their baseline SARS-CoV-2 infection status, dropped consistently after vaccination. Overall, SARS-CoV-2 IFN-{gamma} CD8+ and CD4+ T-cell responses in NHR decreased in post-vaccination specimens. ConclusionThe BNT162b2 COVID-19 vaccine elicits robust SARS-CoV-2-S antibody responses in NHR. Nevertheless, the frequency and magnitude of detectable SARS-CoV-2 IFN-{gamma} T-cell responses after vaccination was lower in NHR compared to controls.

Field evaluation of a rapid antigen test (Panbio COVID-19 Ag Rapid Test Device) for the diagnosis of COVID-19 in primary healthcare centers

We evaluated the Panbio COVID-19 AG Rapid Test Device (RAD) for the diagnosis of COVID-19 in symptomatic patients attended in primary healthcare centers (n=412). Overall specificity and sensitivity of RAD was 100% and 79.6%, respectively, taking RT-PCR as the reference. SARS-CoV-2 could not be cultured from specimens yielding RT-PCR+/RAD- results.

Suitability of Two Rapid Lateral Flow Immunochromatographic Assays for Predicting SARS-CoV-2 Neutralizing Activity of Sera

PurposeAssessment of commercial SARS-CoV-2 immunoassays for their capacity to provide reliable information on sera neutralizing activity is an emerging need. We evaluated the performance of two commercially-available lateral flow immunochromatographic assays (LFIC) (Wondfo SARS-CoV-2 Antibody test and the INNOVITA 2019-nCoV Ab test) in comparison with a SARS-CoV-2 neutralization pseudotyped assay for COVID-19 diagnosis in hospitalized patients, and investigate whether the intensity of the test band in LFIC associates with neutralizing antibody (NtAb) titers. Patients and MethodsNinety sera were included from 51 patients with moderate to severe COVID-19. A green fluorescent protein (GFP) reporter-based pseudotyped neutralization assay (vesicular stomatitis virus coated with SARS-CoV-2 spike protein) was used. Test line intensity was scored using a 4-level scale (0 to 3+). ResultsOverall sensitivity of LFIC assays was 91.1% for the Wondfo SARS-CoV-2 Antibody test, 72.2% for the INNOVITA 2019-nCoV IgG, 85.6% for the INNOVITA 2019-nCoV IgM and 92.2% for the NtAb assay. Sensitivity increased for all assays in sera collected beyond day 14 after symptoms onset (93.9%, 79.6%,93.9% and 93.9%, respectively). Reactivities equal to or more intense than the positive control line ([≥]2+) in the Wondfo assay had a negative predictive value of 100% and a positive predictive value of 96.4% for high NtAb50 titers ([≥]1/160). ConclusionsOur findings support the use of LFIC assays evaluated herein, particularly the Wondfo test, for COVID-19 diagnosis. We also find evidence that these rapid immunoassays can be used to predict high SARS-CoV-2-S NtAb50 titers.

Qualitative assessment of SARS-CoV-2-specific antibody avidity by lateral flow immunochromatographic IgG/IgM antibody assay

Qualitative assessment of SARS-CoV-2-specific antibody avidity was conducted using an urea (6M) dissociation test performed on a lateral flow immunochromatographic IgG/IgM device. We included a total of 76 serum specimens collected from 57 COVID-19 patients, of which 39 tested positive for both IgG and IgM and 37 only for IgG. Sera losing IgG reactivity after urea treatment (n=28) were drawn significantly earlier (P=0.04) after onset of symptoms than those which preserved it (n=48). This assay may be helpful to estimate the time of acquisition of infection in patients with mild to severe COVID-19.

Amplification of human β-glucoronidase gene for appraising the accuracy of negative SARS-CoV-2 RT-PCR results in upper respiratory tract specimens

Real-time reverse transcription polymerase-chain reaction (RT-PCR) is the mainstay of Covid-19 diagnosis. False-negative RT-PCR results may hamper clinical management of patients and hinder the adoption of epidemiological measures to control the pandemic. The current study was aimed at assessing whether amplification of {beta}-glucoronidase (GUSB) gene would help estimate the accuracy of SARS-CoV-2 RT-PCR negative results in upper respiratory tract (URT) specimens. URT specimens that tested negative by SARS-CoV-2 RT-PCR displayed higher GUSB RT-PCR cycle thresholds (CT) (P=0.070) than those testing positive (median, 30.7; range, 27.0-40.0, and median 29.7; range 25.5-36.8, respectively), this reflecting poorer cellularity. Receiver operating characteristic (roc) curve analysis indicated that a CT threshold of 31.2 discriminated best between positive and negative SARS CoV-2 RT-PCRs (area under a curve, 0.66; 95% CI, 0.50-0.81; P=0.08). This cut-off yielded a true negative ratio of 89% and accuracy of 70%. The data suggested that amplification of the GUSB gene by RT-PCR may help to appraise the accuracy of negative SARS-CoV-2 RT-PCR results in patients in whom Covid-19 is eventually diagnosed.

Anti-TNFα therapy and switching in severe uveitis related to Vogt-Koyanagi-Harada syndrome.

The study aimed to describe the effectiveness of switching the anti-TNFα agent when an acceptable clinical response has not been obtained with the first anti-TNFα agent in patients with uveitis in VKH syndrome. Patients diagnosed with VKH syndrome being evaluated from the uveitis unit of a single tertiary hospital from January 1, 2000, to October 30, 2015. Patients who presented uveitis with an inadequate response to a first anti-TNFα and required switching to a second anti-TNFα were selected. Complete clinical response was assumed in patients whose visual acuity was normal and those who showed absence of inflammatory findings (inflammatory cells in the anterior chamber and vitritis) or absence of macular thickening in upon OCT. A systematic review of the literature of anti-TNFα agents in VKH syndrome was performed. Five patients met the criteria of VKH syndrome. Two cases of VKH syndrome with uveitis and inadequate clinical response to an initial anti-TNFα (both IFX) were presented. After switching to Adalimumab (ADA), a satisfactory clinical response was noted in the first month. For the first time, we present two patients with severe uveitis due to VKH syndrome who after inadequately responding to the first anti-TNFα agent showed complete and maintained clinical improvement when switched to a second anti-TNFα agent.