Quantitative SARS-CoV-2 viral-load curves in paired saliva and nasal swabs inform appropriate respiratory sampling site and analytical test sensitivity required for earliest viral detection

Early detection of SARS-CoV-2 infection is critical to reduce asymptomatic and pre-symptomatic transmission, curb the spread of variants, and maximize treatment efficacy. Low-analytical-sensitivity nasal-swab testing is commonly used for surveillance and symptomatic testing, but the ability of these tests to detect the earliest stages of infection has not been established. In this study, conducted between September 2020 and June 2021 in the greater Los Angeles County, California area, initially-SARS-CoV-2-negative household contacts of individuals diagnosed with COVID-19 prospectively self-collected paired anterior-nares nasal-swab and saliva samples twice daily for viral-load quantification by high-sensitivity RT-qPCR and digital-RT-PCR assays. We captured viral-load profiles from the incidence of infection for seven individuals and compared diagnostic sensitivities between respiratory sites. Among unvaccinated persons, testing saliva with a high-analytical-sensitivity assay detected infection up to 4.5 days before viral loads in nasal swabs reached concentrations detectable by low-analytical-sensitivity nasal-swab tests. For most participants, nasal swabs reached higher peak viral loads than saliva, but were undetectable or at lower loads during the first few days of infection. High-analytical-sensitivity saliva testing was most reliable for earliest detection. Our study illustrates the value of acquiring early (within hours after a negative high-sensitivity test) viral-load profiles to guide the appropriate analytical sensitivity and respiratory site for detecting earliest infections. Such data are challenging to acquire but critical to design optimal testing strategies with emerging variants in the current pandemic and to respond to future viral pandemics.

Performance evaluation of the BD SARS-CoV-2 reagents for the BD MAX™ system

Background The RT-qPCR assay for detecting SARS-CoV-2 virus is the favorable approach to test suspected COVID-19 cases. However, discordant results can occur when two or more assays are compared. Variability in analytical sensitivities between assays, among other factors, may account for these differences in reporting. Methods The limits of detection (LOD) for the BD SARS-CoV-2 Reagents for BD MAXTM System ('MAX SARS-CoV-2 assay'), the Biomerieux BioFire® Respiratory Panel 2.1 ('BioFire SARS-CoV-2 assay'), the Roche cobas SARS-CoV-2 assay ('cobas SARS-CoV-2 assay'), and the Hologic Aptima® SARS-CoV-2 assay Panther® ('Aptima SARS-CoV-2 assay') RT-qPCR systems were determined using a total of 84 contrived nasopharyngeal specimens with seven target levels for each comparator. The positive and negative percent agreement (PPA and NPA, respectively) for the MAX SARS-CoV-2 assay were compared to the Aptima SARS-CoV-2 assay in a post-market clinical study utilizing 708 paired nasopharyngeal specimens collected from suspected COVID-19 cases. Discordant results were further tested by the cobas and BioFire SARS-CoV-2 assays. Results The measured LOD for the MAX SARS-CoV-2 assay (251 copies/mL) was comparable to the cobas SARS-CoV-2 assay (298 copies/mL) and the BioFire SARS-CoV-2 assay (302 copies/mL); the Aptima SARS-CoV-2 assay had a LOD of 612 copies/mL. The MAX SARS-CoV-2 assay had a PPA of 100% (95%CI: [97.3%-100.0%]) and a NPA of 96.7% (95%CI: [94.9%-97.9%]) when compared to the Aptima SARS-CoV-2 assay. Conclusions The MAX SARS-CoV-2 assay exhibited a high analytical sensitivity and specificity for SARS-CoV-2 detection. The clinical performance of the MAX SARS-CoV-2 assay agreed with another sensitive EUA cleared assay.

Theoretical framework for retrospective studies of the effectiveness of SARS-CoV-2 vaccines

ABSTRACTObservational studies of the effectiveness of vaccines to prevent COVID-19 are needed to inform real-world use. These are now in planning amid the ongoing rollout of SARS-CoV-2 vaccines globally. While traditional case-control (TCC) and test-negative design (TND) studies feature prominently among strategies used to assess vaccine effectiveness, such studies may encounter important threats to validity. Here we review the theoretical basis for estimation of vaccine direct effects under TCC and TND frameworks, addressing specific natural history parameters of SARS-CoV-2 infection and COVID-19 relevant to these designs. Bias may be introduced by misclassification of cases and controls, particularly when clinical case criteria include common, non-specific indicators of COVID-19. When using diagnostic assays with high analytical sensitivity for SARS-CoV-2 detection, individuals testing positive may be counted as cases even if their symptoms are due to other causes. The TCC may be particularly prone to confounding due to associations of vaccination with healthcare-seeking behavior or risk of infection. The TND reduces but may not eliminate this confounding, for instance if individuals who receive vaccination seek care or testing for less-severe infection. These circumstances indicate the two study designs cannot be applied naively to datasets gathered through public health surveillance or administrative sources. We suggest practical strategies to reduce bias in vaccine effectiveness estimates at the study design and analysis stages.

Cytoplasmic aggregation of uranium in human dopaminergic cells after continuous exposure to soluble uranyl at non-cytotoxic concentrations

ABSTRACTUranium exposure can lead to neurobehavioral alterations in particular of the monoaminergic system, even at non-cytotoxic concentrations. However, the mechanisms of uranium neurotoxicity after non-cytotoxic exposure are still poorly understood. In particular, imaging uranium in neurons at low intracellular concentration is still very challenging. We investigated uranium intracellular localization by means of synchrotron X-ray fluorescence imaging with high spatial resolution (< 300 nm) and high analytical sensitivity (< 1 μg.g-1 per 300 nm pixel). Neuron-like SH-SY5Y human cells differentiated into a dopaminergic phenotype were continuously exposed, for seven days, to a non-cytotoxic concentration (10 μM) of soluble natural uranyl. Cytoplasmic submicron uranium aggregates were observed accounting on average for 62% of the intracellular uranium content. In some aggregates, uranium and iron were co-localized suggesting common metabolic pathways between uranium and iron storage. Uranium aggregates contained no calcium or phosphorous indicating that detoxification mechanisms in neuron-like cells are different from those described in bone or kidney cells. Uranium intracellular distribution was compared to fluorescently labeled organelles (lysosomes, early and late endosomes) and to fetuin-A, a high affinity uranium-binding protein. A strict correlation could not be evidenced between uranium and the labelled organelles, or with vesicles containing fetuin-A. Our results indicate a new mechanism of uranium cytoplasmic aggregation after non-cytotoxic uranyl exposure that could be involved in neuronal defense through uranium sequestration into less reactive species. The remaining soluble fraction of uranium would be responsible for protein binding and the resulting neurotoxic effects.

Androgen deficiency in women and possibilities for its hormonal diagnostics

The authors describe the distribution patterns of free testosterone concentrations in the saliva of women who previously underwent ovariectomy, in postmenopausal women, in those presenting with clinical signs of hyperandrogenism, and in healthy women in the follicular phase of the menstrual cycle. The level of salivary free testosterone in postmenopausal women and after ovariectomy was lower than in younger premenopausal patients. Women with clinical signs of hyperandrogenism showed higher free testosterone levels than the age-matched young healthy subjects. The salivary free testosterone levels in 60-75% of the ovariectomzed, postmenopausal, and hyperandogenic women remained within their normal range in young healthy women. It is concluded that high analytical sensitivity of the chemiluminescent method for the measurement of free testosterone in the saliva makes possible its application to the screening for androgen status of the women at risk of testosterone deficiency.

A new sample isolation procedure for microchemical analysis of functional liver cell heterogeneity.

In conjunction with the investigation of intercellular compartmentation of liver carbohydrate metabolism, a new procedure for isolation of tissue samples from freeze-dried cryosections was developed. It was designed to permit assessment of functional differences between sinusoids of portal and septal origin, and to extend investigation of liver cell heterogeneity along sinusoids to the level of the structural-functional unit. Application of this procedure, together with microchemical assays of high analytical sensitivity, enabled measurement of 50 individual glucose and glucose-6-P values in a single cross-sectional area of about 0.75 mm2 of a liver unit. Preliminary results on the distribution of glucose and glucose-6-P indicated that, in a state of overall glucose release glucose levels were significantly higher in the center than in the periphery of the unit. Overall glucose release by the liver resulted from both release and uptake of glucose along sinusoids. Glucose-6-P was highest in the periphery and decreased toward the center. Microchemical data, furthermore, indicated possible functional heterogeneity of sinusoids, insofar as both glucose and glucose-6-P gradients were steeper in "portal-central" than in "septal-central" sinusoids.