Optimal diagnostic fever thresholds using non-contact infrared thermometers under COVID-19.

Fever screening is an effective method to detect infectors associated with different variants of coronavirus disease 2019 (COVID-19) based on the fact that most infectors with COVID-19 have fever symptoms. Non-contact infrared thermometers (NCITs) are widely used in fever screening. Nevertheless, authoritative data is lacking in defining "fever" at different body surface sites when using NCITs. The purpose of this study was to determine the optimal diagnostic threshold for fever screening using NICTs at different body surface sites, to improve the accuracy of fever screening and provide theoretical reference for healthcare policy. Participants (n = 1860) who were outpatients or emergency patients at Chengdu Women's and Children's Central Hospital were recruited for this prospective investigation from March 1 to June 30, 2021. NCITs and mercury axillary thermometers were used to measure neck, temple, forehead and wrist temperatures of all participants. Receiver operating characteristic curves were used to reflect the accuracy of NCITs. Linear correlation analysis was used to show the effect of age on body temperature. Multilinear regression analysis was used to explore the association between non-febrile participant's covariates and neck temperature. The mean age of participants was 3.45 ± 2.85 years for children and 28.56 ± 7.25 years for adults. In addition 1,304 (70.1%) participants were children (≤12), and 683 (36.7%) were male. The neck temperature exhibited the highest accuracy among the four sites. Further the optimal fever diagnostic thresholds of NCITs at the four body surface measurement sites were neck (36.75 °C, sensitivity: 0.993, specificity: 0.858); temple (36.55 °C, sensitivity: 0.974, specificity: 0.874); forehead (36.45 °C, sensitivity: 0.961, specificity: 0.813); and wrist (36.15 °C, sensitivity: 0.951, specificity: 0.434). Based on the findings of our study, we recommend 36.15, 36.45, 36.55, and 36.75 °C as the diagnostic thresholds of fever at the wrist, forehead, temple and neck, respectively. Among the four surface sites, neck temperature exhibited the highest accuracy.

Fast detection of harmful trace elements in glycyrrhiza using standard addition and internal standard method - laser-induced breakdown spectroscopy (SAIS-LIBS)

Glycyrrhiza is traditional Chinese medicine, whose active compounds have great potential in treating COVID-19. Detecting harmful trace elements of glycyrrhiza has become essential. However, it is not easy to detect trace elements due to the complex matrix of nonstandard glycyrrhiza. Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) can be used in quantitive of nonstandard, but its stability and accuracy are low. To detect trace elements of glycyrrhiza quickly and accurately, this work introduced the standard addition method and internal standard method into LIBS, namely SAIS-LIBS. SAIS-LIBS was applied to determine trace copper and manganese in glycyrrhiza. The results showed that SAIS-LIBS had higher efficiency (<0.3 h), and could be up to 3-25 times more accuracy and stability than CF-LIBS. Furthermore, SAIS-LIBS results and inductively coupled plasma-optical emission spectroscopy (ICP-OES) were very similar (p-values > 0.05). This research provided a foundation for the rapid and accurate detection of harmful trace elements in glycyrrhiza.

In vitro inactivation of SARS-CoV-2 by commonly used disinfection products and methods (preprint)

Background Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is currently a global pandemic, and there is a lack of laboratory studies targeting pathogen resistance.Objective To investigate the effect of selected disinfection products and methods on the inactivation of SARS-CoV-2.Methods We used quantitative suspension testing to evaluate the effectiveness of the disinfectant/method.Results Available chlorine of 250 mg/L, 500 mg/L, and 1000 mg/L required 20 min, 5 min, and 0.5 min to efficiently inactivate SARS-CoV-2, respectively. A 600-fold dilution of 17% concentration of di-N-decyldimethylammonium bromide (283 mg/L) and the same concentration of di-N-decyldimethylammonium chloride required only 0.5 min to efficiently inactivate the virus. Ethanol, at 30% concentration for 1 min, and 40% and above for 0.5 min, could efficiently inactivate SARS-CoV-2. Heat takes approximate 30 min at 56°C, or 10 min above 70°C, or 5 min above 90°C to inactivate the virus.Conclusions The chlorinated disinfectants, Di-N-decyldimethylammonium bromide / chloride, ethanol, and heat were effective in inactivating SARS-CoV-2. The response of SARS-CoV-2 to disinfectants is very similar to that of SARS-CoV.

Development of a lateral flow immunoassay strip for rapid detection of IgG antibody against SARS-CoV-2 virus.

The ongoing worldwide SARS-CoV-2 epidemic clearly has a tremendous influence on public health. Molecular detection based on oral swabs was used for confirmation of SARS-CoV-2 infection. However, high false negative rates were reported. We describe here the development of a point-of-care (POC) serological assay for the detection of IgG antibody against SARS-CoV-2. The principle of a lateral flow immunoassay strip (LFIAs) consists of fixing SARS-CoV-2 nucleocapsid protein to the surface of the strip and coupling anti-human IgG with colloidal gold nanoparticles (Au NPs). A series of parameters of this method were optimized, including the concentration of coating antigen, BSA blocking concentration and pH value for conjugation. The entire detection process took 15-20 min with a volume of 80 µL of the analyte solution containing 10 µL of serum and 70 µL sample diluent. The performance of the established assay was evaluated using serum samples of the clinically diagnosed cases of Coronavirus Disease 2019 (COVID-19). Our results indicated that the LFIAs for SARS-CoV-2 had satisfactory stability and reproducibility. As a result, our fast and easy LFIAs could provide a preliminary test result for physicians to make the correct diagnosis of SARS-CoV-2 infections along with alternative testing methods and clinical findings, as well as seroprevalence determination, especially in low-resource countries.

Rapid Detection of IgM Antibodies against the SARS-CoV-2 Virus via Colloidal Gold Nanoparticle-Based Lateral-Flow Assay.

Last year, the novel coronavirus disease (COVID-19) emerged in Wuhan, and it has rapidly spread to many other countries and regions. COVID-19 exhibits a strong human-to-human transmission infectivity and could cause acute respiratory diseases. Asymptomatic carriers are able to infect other healthy persons, and this poses a challenge for public health; the World Health Organization (WHO) has already announced COVID-19 as a global pandemic. Nucleic acid testing, considered as the current primary method for diagnosing COVID-19, might lead to false negatives and is difficult to be applied for every suspected patient because of the existence of asymptomatic carriers. Meanwhile, detecting specific antibodies in blood, such as the IgM antibody, against the SARS-CoV-2 virus is another choice for COVID-19 diagnosis, as it is widely accepted that IgM is an important indicator in the acute infection period. In this study, a colloidal gold nanoparticle-based lateral-flow (AuNP-LF) assay was developed to achieve rapid diagnosis and on-site detection of the IgM antibody against the SARS-CoV-2 virus through the indirect immunochromatography method. For preparing AuNP-LF strips, the SARS-CoV-2 nucleoprotein (SARS-CoV-2 NP) was coated on an analytical membrane for sample capture, and antihuman IgM was conjugated with AuNPs to form the detecting reporter. Optimization of AuNP-LF assay was carried out by altering the pH value and the amount of antihuman IgM. The performance of AuNP-LF assay was evaluated by testing serum samples of COVID-19 patients and normal humans. The results were compared with the real-time polymerase chain reaction. The sensitivity and specificity of AuNP-LF assay were determined to be 100 and 93.3%, respectively, and an almost perfect agreement was exhibited by Kappa statistics (κ coefficient = 0.872). AuNP-LF assay showed outstanding selectivity in the detection of IgM against the SARS-CoV-2 virus with no interference from other viruses such as severe fever with thrombocytopenia syndrome virus (SFTSV) and dengue virus (DFV). AuNP-LF assay was able to achieve results within 15 min and needed only 10-20 µL serum for each test. As a whole, in the light of its advantages such as excellent specificity and stability, easy operation, low cost, and being less time-consuming, AuNP-LF assay is a feasible method for the diagnosis of COVID-19 in primary hospitals and laboratories, especially in emergency situations in which numerous samples need to be tested on time.

Association of viral load with serum biomakers among COVID-19 cases.

Since SARS-CoV-2 spreads rapidly around the world, data have been needed on the natural fluctuation of viral load and clinical indicators associated with it. We measured and compared viral loads of SARS-CoV-2 from pharyngeal swab, IgM anti-SARS-CoV-2, CRP and SAA from serum of 114 COVID-19 patients on admission. Positive rates of IgM anti-SARS-CoV-2, CRP and SAA were 80.7%, 36% and 75.4% respectively. Among IgM-positive patients, viral loads showed different trends among cases with different severity, While viral loads of IgM-negative patients tended to increase along with the time after onset. As the worsening of severity, the positive rates of CRP and SAA also showed trends of increase. Different CRP/SAA type showed associations with viral loads in patients in different severity and different time after onset. Combination of the IgM and CRP/SAA with time after onset and severity may give suggestions on the viral load and condition judgment of COVID-19 patients.