ABSTRACT
Surveillance tools to estimate infection rates in young populations are essential to guide recommendations for school reopening and management during viral epidemics. Ideally, field-deployable non-invasive, sensitive techniques are required to detect low viral load exposures among asymptomatic children. We determined SARS-CoV-2 antibody conversion by high-throughput Luminex assays in saliva samples collected weekly in 1,509 children and 396 adults in 22 Summer schools and 2 pre-schools in 27 venues in Barcelona, Spain, from June 29th to July 31st 2020, between the first and second COVID-19 pandemic waves. Saliva antibody conversion defined as [≥]4-fold increase in IgM, IgA and/or IgG levels to SARS-CoV-2 antigens between two visits over a 5-week period was 3.22% (49/1518), or 2.36% if accounting for potentially cross-reactive antibodies, six times higher than the cumulative infection rate (0.53%) by weekly saliva RT-PCR screening. IgG conversion was higher in adults (2.94%, 11/374) than children (1.31%, 15/1144) (p=0.035), IgG and IgA levels moderately increased with age, and antibodies were higher in females. Most antibody converters increased both IgG and IgA antibodies but some augmented either IgG or IgA, with a faster decay over time for IgA than IgG. Nucleocapsid rather than spike was the main antigen target. Anti-spike antibodies were significantly higher in individuals not reporting symptoms than symptomatic individuals, suggesting a protective role against COVID-19. To conclude, saliva antibody profiling including three isotypes and multiplexing antigens is a useful and more user-friendly tool for screening pediatric populations to determine SARS-CoV-2 exposure and guide public health policies during pandemics.
ABSTRACT
COVID-19 affects children to a lesser extent than adults but they can still get infected and transmit SARS-CoV-2 to their contacts. Field deployable non-invasive sensitive diagnostic techniques are needed to evaluate the infectivity dynamics of the coronavirus in pediatric populations and guide public health interventions. We evaluated the utility of high-throughput Luminex-based assays applied to saliva samples to quantify IgM, IgA and IgG antibodies against five SARS-CoV-2 spike (S) and nucleocapsid (N) antigens in the context of a contacts and infectivity longitudinal study. We compared the antibody levels obtained in saliva versus serum/plasma samples from a group of children and adults tested weekly by RT-PCR over 35 days and diagnosed as positive (n=58), and a group of children and adults who consistently tested negative over the follow up period (n=61), in the Summer of 2020 in Barcelona, Spain. Antibody levels in saliva samples from individuals with confirmed RT-PCR diagnosis of SARS-CoV-2 infection were significantly higher than in negative individuals and correlated with those measured in sera/plasmas. Higher levels of anti-S IgG were found in asymptomatic individuals that could indicate protection against disease in infected individuals. Higher anti-S IgG and IgM levels in serum/plasma and saliva, respectively, in infected children compared to infected adults could also be related to stronger clinical immunity in them. Among infected children, males had higher levels of saliva IgG to N and RBD than females. Despite overall correlation, individual clustering analysis suggested that responses that may not be detected in blood could be patent in saliva, and vice versa, and therefore that both measurements are complementary. In addition to serum/plasma, measurement of SARS-CoV-2-specific saliva antibodies should be considered as a complementary non-invasive assay to better estimate the percentage of individuals who have experienced coronavirus infection. Saliva antibody detection could allow determining COVID-19 prevalence in pediatric populations, alternative to bleeding or nasal swab, and serological diagnosis following vaccination.
ABSTRACT
BackgroundThere is an urgent need to curb COVID-19 pandemic through early identification of asymptomatic but infectious cases. We aimed to validate and implement an optimised screening method for detection of SARS-CoV-2 RNA combining use of self-collected raw saliva samples, single-step heat-treated virus inactivation and RNA extraction, and direct RT-qPCR. Methods and findingsThe study was conducted in Sant Joan de Deu University Hospital (Barcelona, Spain), including: i) analytical validation against standard RT-qPCR in saliva samples; ii) diagnostic validation against standard RT-qPCR using paired saliva-nasopharyngeal samples obtained from asymptomatic teenagers and young and older adults in a youth sports academy; and iii) high throughput pilot screening of asymptomatic health workers and other staff in the study site. The proposed method had comparable analytical performance to standard RT-qPCR in saliva. Diagnostic validation included saliva samples self-collected with supervision by 173 participants during 9-12 weeks and nasopharyngeal samples collected from them. At baseline, all participants (100.0%) were negative for SARS-CoV-2 in both paired saliva-nasopharyngeal samples. In the following weeks, standard RT-qPCR yielded 23 positive results in nasopharyngeal samples whereas paired saliva specimens yielded 22 (95.7%) positive and one inconclusive result. A total of 2,709 participants engaged in the pilot screening, with high rate of participation (83.4% among health workers). Only 17 (0.6%) of saliva samples self-collected by participants in an unsupervised manner were invalid. Saliva was positive in 24 (0.9%) out of 2,692 valid specimens and inconclusive in 27 (1.0%). All 24 saliva-positive participants and 4 with saliva inconclusive results were positive by standard RT-qPCR in nasopharyngeal samples. The pilot showed potential for rapid analytical workflow (up to 384 batched samples can be processed in <2 hours). ConclusionDirect RT-qPCR on self-collected raw saliva is a simple, rapid, and accurate method with potential to be scaled up for enhanced SARS-CoV-2 community-wide screening.
ABSTRACT
OBJECTIVES: To assess the kinetics of procalcitonin (PCT) and C-reactive protein (CRP) in newborns after cardiothoracic surgery (CS), with and without cardiopulmonary bypass, and to assess whether PCT was better than CRP in identifying sepsis in the first 72 hours after CS. PATIENTS AND METHODS: This is a prospective study of newborns admitted to the neonatal intensive care unit after CS. INTERVENTIONS: PCT and CRP were sequentially drawn 2 hours before surgery and at 0, 12, 24, 48, and 72 hours after surgery. RESULTS: A total of 65 patients were recruited, of which 14 were excluded because of complications. We compared the kinetics of PCT and CRP after CS in bypass and non-bypass groups without sepsis; there were no differences in the PCT values at any time (24 hours, P = 0.564; 48 hours, P = 0.117; 72 hours, P = 0.076). Thirty-five patients needed bypass, of whom four were septic (11.4%). Significant differences were detected in the PCT values on comparing the septic group to the nonseptic group at 48 hours after cardiopulmonary bypass (P = 0.018). No differences were detected in the CRP values in these groups. A suitable cutoff for sepsis diagnosis at 48 hours following bypass would be 5 ng/mL, with optimal area under the curve of 0.867 (confidence interval 0.709-0.958), P < 0.0001, and sensitivity and specificity of 87.5% (29.6-99.7) and 72.6% (53.5-86.4), respectively. CONCLUSION: This is a preliminary study but PCT seems to be a good biomarker in newborns after CS. Values over 5 ng/mL at 48 hours after CS should alert physicians to the high risk of sepsis in these patients.
ABSTRACT
OBJECTIVE: To determine whether procalcitonin discriminates between postcardiopulmonary bypass inflammatory syndrome and infectious complication in children better than does C-reactive protein. DESIGN: Prospective study of children admitted to the intensive care unit after cardiopulmonary bypass. PATIENTS: Classified according to a diagnosis of systemic inflammatory response syndrome and bacterial infection or systemic inflammatory response syndrome but no bacterial infection. Two hundred thirty-one cases were recruited. MEASUREMENT AND MAIN RESULTS: Procalcitonin, C-reactive protein, and leukocyte count were measured daily from surgery until day 3. Twenty-two patients were infected (9.5%). Significant differences were detected in the procalcitonin values of the infected group vs. the noninfected group, especially at day 2 (p = .000). There were no differences in the C-reactive protein values. The optimal cutoff for procalcitonin was >2 ng/mL at day 1 and above 4 ng/mL at the day 2. There was a greater sensitivity and specificity than with C-reactive protein as an infection predictor. CONCLUSION: Procalcitonin is useful in the diagnosis of bacterial infection after cardiopulmonary bypass. Because procalcitonin kinetics are different in postcardiopulmonary bypass patients, the cutoff to diagnose infection should be different from the normal cutoff.
