Comparative sensitivity evaluation for 122 CE-marked rapid diagnostic tests for SARS-CoV-2 antigen, Germany, September 2020 to April 2021

Establishing quality assurance for COVID-19 antigen tests in the Indo Pacific Region: A multi-site implementation study

BACKGROUND

Quality assurance programs (QAPs) are used to evaluate the analytical quality of a diagnostic test and provide feedback to improve quality processes in testing. Rapid diagnostic tests were used in both laboratory and non-laboratory settings to diagnose COVID-19, although varied in reported performance. We aimed to design and implement a QAP for antigen rapid diagnostic tests (Ag-RDTs) for COVID-19 in Cambodia, Lao PDR, and Papua New Guinea.

METHODS

Inactivated SARS-CoV-2 material derived from cell culture of Wildtype, Delta, and Omicron isolates were used to manufacture 435 quality control (QC) panels (consisting of a single positive and negative sample) and 36 external quality assessment (EQA) panels for use across 15 sites in accordance with provided training and protocols.

RESULTS

In total, 369 QC results and 112 EQA results were submitted by electronic reporting or paper forms by two countries. 19·3 % (34/176) positive and 99·5 % (192/193) negative samples were correctly reported in the QC, and 37·5 % (30/80) positive and 97·5 % (39/40) negative samples were correctly reported in the EQA.

CONCLUSION

This QAP demonstrates the importance of operator training and the design of QAP materials, which may have contributed to the high rate of false-negative interpretations in known COVID-19 positive samples. The implementation of this project, to our knowledge the first of its kind in the region and one of only a few globally, emphasised the importance of quality assurance principles, including non-laboratory community testing sites, to promote diagnostic quality for COVID-19 testing.

Development of a Peptide Aptamer-Based TRFIA for the Quantitive Detection of SARS-CoV-2 Nucleocapsid Protein

This study, we employed computer-aided design to develop 27 peptide aptamers, and initially screened 11 candidates with binding energies less than - 6.0 kcal/mol. Subsequently, three peptide aptamers with strong specificity were selected using a direct time-resolved fluorescence immunoassay (TRFIA). Peptide aptamer B3, in combination with monoclonal antibody R001, was used to construct a TRFIA-based sandwich assay system. The performance of this system was evaluated concerning sensitivity, specificity, and reproducibility, and was further tested using 20 simulated pharyngeal swab samples. The dominant peptide aptamer, B3(RGQGVPI), was identified as the most promising candidate. This peptide demonstrated high specificity for the SARS-CoV-2 nucleocapsid (N) protein, with the lowest detectable concentration of 203.78 pg/mL. Importantly, the peptide had no cross-reactions with other potential interferents, including RSV, Flu A, and MP, confirming its specificity. The assay also exhibited good reproducibility, with coefficients of variation of 11.33% and 8.00% at different concentrations in pharyngeal swab samples. Additionally, the LOB and LOD in clinical samples were 31.59 pg/mL and 243.70 pg/mL and the correlation coefficient R2 was 0.9784, which indicated that the method had good resistance to clinical interference. In this study, we successfully developed a sandwich TRFIA method based on the peptide aptamer B3-R001, which can be used to quantitatively measure the SARS-CoV-2 N protein level in pharyngeal swabs. Compared to antibodies, peptide aptamers are easily synthesized, inexpensive, and show great potential for clinical applications. This method provides a novel approach for rapidly detecting viral pathogens, contributing to the advancement of diagnostic tools.

A Truncated Multi-Thiol Aptamer-Based SARS-CoV-2 Electrochemical Biosensor: Towards Variant-Specific Point-of-Care Detection with Optimized Fabrication

With the goal of fast and accurate diagnosis of infectious diseases, this study presents a novel electrochemical biosensor that employs a refined aptamer (C9t) for the detection of spike (S) protein SARS-CoV-2 variants in a flexible multielectrode aptasensor array with PoC capabilities. Two aptamer modifications were employed: removing the primer binding sites and including two dithiol phosphoramidite anchor molecules. Thus, reducing fabrication time from 24 to 3 h and increasing the stability and sparseness for multi-thiol aptasensors compared to a standard aptasensor using single thiols, without a reduction in aptamer density. The biosensor fabrication, optimization, and detection were verified in detail by electrochemistry, QCM-D, SPR, and XPS. The analyte-receptor binding was further confirmed spectroscopically at the level of individual molecules by AFM-IR. The aptasensor possesses a low limit of detection (8.0 fg/mL), the highest sensitivity reported for S protein (209.5 signal per concentration decade), and a wide dynamic detection range (8.0 fg/mL-38 ng/mL) in nasopharyngeal samples, covering the clinically relevant range. Furthermore, the C9t aptasensor showed high selectivity for SARS-CoV-2 S proteins over biomarkers for MERS-CoV, RSV, and Influenza. Even more, it showed a three times higher sensitivity for the Omicron in comparison to the Wuhan strain (wild type), alpha, and beta variants of the SARS-CoV-2 virus. Those results demonstrate the creation of an affordable and variant-selective refined C9t aptasensor that outperformed current rapid diagnosis tests.

Multiplex molecular assays for the laboratory-based and point-of-care diagnosis of infections caused by seasonal influenza, COVID-19, and RSV

INTRODUCTION

SARS-CoV-2, seasonal influenza, and respiratory syncytial virus (RSV) are major causes of acute respiratory infections in all age groups and responsible for an enormous socio-economic burden. The recently coined term 'tripledemic' describes co-circulation of these three viruses, a novel epidemiological paradigm that poses profound public health implications.

AREAS COVERED

Real-time reverse transcription polymerase chain reaction (RT-PCR) is now considered the reference method for the diagnosis of SARS-CoV-2, influenza, and RSV infections. Syndromic-based multiplex RT-PCR panels that simultaneously detect several respiratory viruses have become increasingly common. This review explores available molecular diagnostics (MDx) platforms for the diagnosis of SARS-CoV-2, influenza, and RSV in the same biological sample. Within some limitations of the published validation and diagnostic accuracy studies, both laboratory-based and point-of-care multiplex panels proved highly performant in identifying SARS-CoV-2, influenza A, influenza B, and RSV. Improved operational efficiency and faster turnaround times make these assays potentially cost-effective or even cost-saving.

EXPERT OPINION

The adoption of multiplex MDx assays for the contemporary detection of SARS-CoV-2, influenza, RSV, and other respiratory pathogens will likely increase in the next few years. To maximize the clinical usefulness and cost-effectiveness of these assays, locally issued guidelines and protocols on their implementation should be adopted.

Comparison of diagnostic accuracy of rapid antigen tests for COVID-19 compared to the viral genetic test in adults: a systematic review and meta-analysis

OBJECTIVE

The objective of this review was to determine the diagnostic accuracy of the currently available and upcoming point-of-care rapid antigen tests (RATs) used in primary care settings relative to the viral genetic real-time reverse transcriptase polymerase chain reaction (RT-PCR) test as a reference for diagnosing COVID-19/SARS-CoV-2 in adults.

INTRODUCTION

Accurate COVID-19 point-of-care diagnostic tests are required for real-time identification of SARS-CoV-2 infection in individuals. Real-time RT-PCR is the accepted gold standard for diagnostic testing, requiring technical expertise and expensive equipment that are unavailable in most primary care locations. RATs are immunoassays that detect the presence of a specific viral protein, which implies a current infection with SARS-CoV-2. RATs are qualitative or semi-quantitative diagnostics that lack thresholds that provide a result within a short time frame, typically within the hour following sample collection. In this systematic review, we synthesized the current evidence regarding the accuracy of RATs for detecting SARS-CoV-2 compared with RT-PCR.

INCLUSION CRITERIA

Studies that included nonpregnant adults (18 years or older) with suspected SARS-CoV-2 infection, regardless of symptomology or disease severity, were included. The index test was any available SARS-CoV-2 point-of-care RAT. The reference test was any commercially distributed RT-PCR-based test that detects the RNA genome of SARS-CoV-2 and has been validated by an independent third party. Custom or in-house RT-PCR tests were also considered, with appropriate validation documentation. The diagnosis of interest was COVID-19 disease and SARS-CoV-2 infection. This review considered cross-sectional and cohort studies that examined the diagnostic accuracy of COVID-19/SARS-CoV-2 infection where the participants had both index and reference tests performed.

METHODS

The keywords and index terms contained in relevant articles were used to develop a full search strategy for PubMed and adapted for Embase, Scopus, Qinsight, and the WHO COVID-19 databases. Studies published from November 2019 to July 12, 2022, were included, as SARS-CoV-2 emerged in late 2019 and is the cause of a continuing pandemic. Studies that met the inclusion criteria were critically appraised using QUADAS-2. Using a customized tool, data were extracted from included studies and were verified prior to analysis. The pooled sensitivity, specificity, positive predictive, and negative predictive values were calculated and presented with 95% CIs. When heterogeneity was observed, outlier analysis was conducted, and the results were generated by removing outliers.

RESULTS

Meta-analysis was performed on 91 studies of 581 full-text articles retrieved that provided true-positive, true-negative, false-positive, and false-negative values. RATs can identify individuals who have COVID-19 with high reliability (positive predictive value 97.7%; negative predictive value 95.2%) when considering overall performance. However, the lower level of sensitivity (67.1%) suggests that negative test results likely need to be retested through an additional method.

CONCLUSIONS

Most reported RAT brands had only a few studies comparing their performance with RT-PCR. Overall, a positive RAT result is an excellent predictor of a positive diagnosis of COVID-19. We recommend that Roche's SARS-CoV-2 Rapid Antigen Test and Abbott's BinaxNOW tests be used in primary care settings, with the understanding that negative results need to be confirmed through RT-PCR. We recommend adherence to the STARD guidelines when reporting on diagnostic data.

REVIEW REGISTRATION

PROSPERO CRD42020224250.

Fused Audio Instance and Representation for Respiratory Disease Detection

Audio-based classification techniques for body sounds have long been studied to aid in the diagnosis of respiratory diseases. While most research is centered on the use of coughs as the main acoustic biomarker, other body sounds also have the potential to detect respiratory diseases. Recent studies on the coronavirus disease 2019 (COVID-19) have suggested that breath and speech sounds, in addition to cough, correlate with the disease. Our study proposes fused audio instance and representation (FAIR) as a method for respiratory disease detection. FAIR relies on constructing a joint feature vector from various body sounds represented in waveform and spectrogram form. We conduct experiments on the use case of COVID-19 detection by combining waveform and spectrogram representation of body sounds. Our findings show that the use of self-attention to combine extracted features from cough, breath, and speech sounds leads to the best performance with an area under the receiver operating characteristic curve (AUC) score of 0.8658, a sensitivity of 0.8057, and a specificity of 0.7958. Compared to models trained solely on spectrograms or waveforms, the use of both representations results in an improved AUC score, demonstrating that combining spectrogram and waveform representation helps to enrich the extracted features and outperforms the models that use only one representation. While this study focuses on COVID-19, FAIR's flexibility allows it to combine various multi-modal and multi-instance features in many other diagnostic applications, potentially leading to more accurate diagnoses across a wider range of diseases.

Development and Diagnosis Performance of IgM-Based Rapid Antigen Test for Early Detection of SARS-CoV-2 Infection in a Large Cohort of Suspected COVID-19 Cases - USA, Poland, and Sweden, 2021-2022

Introduction

Antigen testing has been crucial in effectively managing the coronavirus disease 2019 (COVID-19) pandemic. This study evaluated the clinical performance of a nasopharyngeal swab (NPS)-based antigen rapid diagnostic test (Ag-RDT) compared to the gold standard real-time reverse transcription-polymerase chain reaction (RT-PCR) for early detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Methods

We developed an IgM-based rapid antigen test for early detection of SARS-CoV-2 infection. Between July 2021 and January 2022, we analyzed 1,030 NPS samples from participants at three centers in different countries, using both antigen rapid diagnostic tests (Ag-RDT) and RT-PCR.

Results

The Ag-RDT demonstrated minimal detection limits as low as 0.1 ng/mL for recombinant N antigen and 100 TCID50/mL for heat-inactivated SARS-CoV-2 virus. Specificity assessments involving four human coronaviruses and 13 other respiratory viruses showed no cross-reactivity. The Ag-RDT assay (ALLtest) exhibited high sensitivity (93.18%-100%) and specificity (99.67%-100%) across all centers. Factors such as cycle threshold (Ct) values and the timing of symptoms since onset were influential, with sensitivity increasing at lower Ct values (<30) and within the first week of symptoms.

Conclusion

The ALLtest Ag-RDT demonstrated high reliability and significant potential for diagnosing suspected COVID-19 cases.

Comparison of the diagnostic accuracy of the Pluslife Mini Dock RHAM technology with Abbott ID Now and Cepheid GenXpert: A retrospective evaluation study

Rapid and sensitive detection of pathogens is critical in interrupting the transmission chain of infectious diseases. Currently, real-time (RT-)PCR represents the gold standard for the detection of SARS-CoV-2. RNase HII-assisted amplification (RHAM) is a promising technology, enabling reliable point-of-care (PoC) testing; however, its diagnostic accuracy has not yet been investigated. The present study compared the Pluslife Mini Dock (RHAM technology), with Abbott ID Now and Cepheid GeneXpert IV. The positive percent agreement (PPA) and negative percent agreement (NPA) were determined in 100 SARS-CoV-2 positive and 210 SARS-CoV-2 negative samples. Further, the reliability of the Pluslife Mini Dock was investigated in different SARS-CoV-2 variants (Delta and Omicron subvariants). The PPA was 99.00% for Pluslife, 100.00% for Abbott ID Now, and 99.00% for Cepheid GeneXpert, with an NPA of 100.00%, 98.90%, and 93.72%, respectively. Abbott ID Now demonstrated the highest rate of invalid results. All SARS-CoV-2 analysed variants were detected by the Pluslife device. Altogether, the Pluslife Mini Dock demonstrated a PPA of 99.16% (235/237) for CT < 36 and an NPA of 100.00% (313/313), respectively. In conclusion, the Pluslife Mini Dock demonstrated better analytical performance than Abbott ID Now and Cepheid GeneXpert IV, representing a highly accurate and rapid PoC alternative to RT-PCR.

Diagnostic performance of rapid antigen tests (RAT) for COVID-19 and factors associated with RAT-negative results among RT-PCR-positive individuals during Omicron BA.2, BA.5 and XBB.1 predominance

BACKGROUND

While numerous studies have evaluated the real-world performance of rapid antigen tests (RATs), data on the effect of Omicron sublineages such as XBB and reinfections on RAT performance is limited. We assessed the performance of RATs and factors associated with RAT-negative results among individuals who tested SARS-CoV-2-positive by reverse transcription-polymerase chain reaction (RT-PCR).

METHODS

We conducted a retrospective study among Singapore residents who underwent testing for SARS-CoV-2 with RAT (Acon Flowflex or SD Biosensor) and RT-PCR in the same clinical encounter between 9 May 2022 and 21 November 2022. RT-PCR served as a reference standard for RAT performance. Logistic regression was used to estimate the odds ratios (OR) of factors associated with negative RAT results among RT-PCR-positive cases.

RESULTS

Of 8,620 clinical encounters analysed, 3,519 (40.8%) were SARS-CoV-2-positive on RT-PCR. Overall sensitivity and specificity of RAT was 84.6% (95% CI 83.3-85.7%) and 99.4% (95% CI 99.1-99.6%) respectively. Acon Flowflex consistently achieved higher sensitivity and specificity than SD Biosensor test kit. Among RT-PCR-positive cases, individuals who had a previous documented SARS-CoV-2 infection, coinfection with another respiratory pathogen or tested ≥ 6 days from symptom onset had higher odds of testing RAT-negative, but the associations were attenuated after adjustment for cycle threshold values (proxy for viral load). There was no significant difference in RAT performance between Omicron sublineages BA.2, BA.5 and XBB.1.

CONCLUSION

Diagnostic performance of RAT was not affected by changes in predominant circulating Omicron sublineages. However, reinfection cases may be under ascertained by RAT. In individuals with a previous SARS-CoV-2 infection episode or symptom onset ≥ 6 days prior to testing, a confirmatory RT-PCR may be considered if there is high clinical suspicion.

Diagnostic performance of rapid antigen testing for SARS-CoV-2: the COVid-19 AntiGen (COVAG) extension study

Background

This study is the extension of the COVAG study. We compared two RATs, the Panbio COVID-19 Ag Rapid Test (Abbott) and the SD Biosensor Q SARS-CoV-2 Rapid Antigen Test (Roche), against RT-PCR on the foil of new variants.

Methods

We included 888 all-comers at a diagnostic center between October 20, 2021, and March 18, 2022. RT-PCR-positive samples with a Ct value ≤32 were examined for SARS-CoV-2 variants.

Findings

The sensitivity of the Abbott-RAT and Roche-RAT were 65 and 67%, respectively. For both RATs, lower Ct values were significantly correlated with higher sensitivity. For samples with Ct values ≤25, the sensitivities of the Roche-RAT and of the Abbott-RAT were 96 and 95%, for Ct values 25-30 both were 19%, and for Ct values ≥30 they were 6 and 2%, respectively. The RATs had substantially higher sensitivities in symptomatic than asymptomatic participants (76, 77%, vs. 29, 31%, for Abbott-RAT, Roche-RAT, respectively) and in participants referred to testing by their primary care physician (84, 85%) compared to participants who sought testing due to referral by the health department (55, 58%) or a warning by the Corona-Warn-App (49, 49%). In persons with self-reported previous COVID-19 sensitivities were markedly lower than in patients without previous COVID-19: 27% vs. 75% for Roche-RAT and 27% vs. 73% for Abbott-RAT. We did not find significant correlation between vaccination status and sensitivity. The Omicron variant was detected with a sensitivity of 94 and 92%, the delta variant with a sensitivity of 80 and 80% for Abbott-RAT and Roche-RAT, respectively. This difference is attributable to the lower Ct values of the Omicron samples compared to the Delta samples. When adjusted for the Ct value, a multivariate logistic regression did not show a significant difference between Omicron and Delta. In terms of sensitivity, we found no significant difference between the wild-type and the Omicron and Delta variants, but a significantly lower sensitivity to the alpha variant compared to the other variants.The specificities were > 99% overall.

Usefulness of the Rapid Antigen Test in Detecting SARS-CoV-2 for Infection Control in Hospitals

BACKGROUND

We aimed at evaluating the diagnostic performance of rapid antigen test (RAT) compared to polymerase chain reaction (PCR) for severe acute respiratory syndrome coronavirus 2 and the possible transmission of infection to close contacts from patients with negative RAT and positive PCR results.

MATERIALS AND METHODS

Patients/guardians urgently requiring admission to the ward on the same day had been hospitalized with RAT-negative result before the PCR results were available. We performed an epidemiologic investigation of the close contacts of those with negative RAT but positive PCR results after hospitalization.

RESULTS

A total of 4,237 RATs were performed from March to August 2022. When the PCR test was used as the reference, RAT had a sensitivity of 28.8% (17/59; 95% confidence interval [CI], 17.8 - 42.1), a specificity of 100% (4,220/4,220; 95% CI, 99.9 - 100.0), a positive predictive value of 100.0% (17/17; 95% CI, 100.0 - 100.0), and a negative predictive value of 99.0% (4,178/4,220; 95% CI, 99.3 - 99.8). The epidemiologic investigation revealed that among the 32 patients with negative RAT and subsequent positive PCR results after admission into multi-patient room, two (6.3%) showed secondary coronavirus disease 2019.

CONCLUSION

The secondary transmission rate from patients with negative RAT and positive PCR results was low. Our data suggest that RAT may be useful for rapid exclusion of high transmissible cases. However, further evaluation using whole genome sequencing is needed to determine the potential for transmissibility in cases showing a negative RAT but a positive PCR result.

Comparison of pre-labelled primers and nucleotides as DNA labelling method for lateral flow detection of Legionella pneumophila amplicons

Labelling of nucleic acid amplicons during polymerase chain reaction (PCR) or isothermal techniques is possible by using both labelled primers and labelled nucleotides. While the former is the widely used method, the latter can offer significant advantages in terms of signal enhancement and improving the detection limit of an assay. Advantages and disadvantages of both methods depend on different factors, including amplification method, detection method and amplicon length. In this study, both methods for labelling PCR products for lateral flow assay (LFA) analysis (LFA-PCR) were analysed and compared. It was shown that labelling by means of nucleotides results in an increase in label incorporation rates. Nonetheless, this advantage is negated by the need for post-processing and competitive interactions. In the end, it was possible to achieve a detection limit of 3 cell equivalents for the detection of the Legionella-DNA used here via primer labelling. Labelling via nucleotides required genomic DNA of at least 3000 cell equivalents as starting material as well as an increased personnel and experimental effort.

The swab site of the upper airways influences the diagnostic sensitivity for the omicron variant of SARS-CoV-2

The cycle-threshold-value (CT -value) is a quantitative value of the polymerase chain reaction (PCR), which represents the gold standard for the detection of severe acute respiratory syndrome coronavirus 2 (SARS CoV 2). The CT -value can be used to indicate the viral load in swabs of the airways. The collection of a specimen is the only part of the testing process, which is performed manually and carries, therefore, a high potential for increasing measurement variability. The comparison of different PCR results is often difficult since the exact swabbing technique of each test and how do swabs relate in a direct comparison is unknown. For these reasons, the infection course in a patient can be hard infer even after multiple swabs. As the Omicron variant spread from 06/2022 to 08/2022, all common modalities of the upper airway swabs (nasopharyngeal, oropharyngeal, combined naso-oropharyngeal, nasal orifice swabs as well as swabs of the buccal mucosa), which were performed on patients with a suspected infection with SARS CoV 2. RT-PCR was used for SARS CoV 2 RNA detection and the sample comparison was based on the CT -values obtained. Viral loads can vary significantly depending on the swab sites of the upper airways. For the maximum clinical sensitivity, a combined naso-oropharyngeal swab should be considered. In case a single point and single sample measurement is the norm, a nasopharyngeal swab can deliver the highest viral load at the presumed beginning of the infection. Furthermore, the findings of this study can be valuable to correctly interpret results of different PCR with different sampling techniques.

[From the practice of monitoring SARS-CoV-2 test sites in the city of Cologne]

In spring 2021, a law for the nationwide opening of test centers in Germany was passed. The local health department fulfilled the task of monitoring the test centers that subsequently opened throughout Cologne regarding the infectious and hygienic risks. Inspections were carried out using structured checklists. A retrospect evaluation of the identified deficiencies was run for the period between March 15 and July 31, 2021. In 84% of the cases, hygienic deficiencies were found when the test sites were inspected for the first time. 35% of the test sites were closed immediately, most of them temporarily. These first results provide information on frequent and important hygienic problems of the rapid set up of test sites and important advice for avoiding those and thus protecting employees and test persons.

Application of Octenidine into Nasal Vestibules Does Not Influence SARS-CoV-2 Detection via PCR or Antigen Test Methods

The targeted or universal decolonization of patients through octenidine for nasal treatment and antiseptic body wash for 3 to 5 days prior elective surgery has been implemented in several surgical disciplines in order to significantly reduce surgical site infections (SSIs) caused by Staphylococcus aureus carriage. However, as most healthcare facilities also screen patients on admission for pilot infection, it is imperative that a prophylactic nasal decolonization procedure not yield a false negative SARS-CoV-2 status in otherwise positive patients. We assessed the effect of a commercially available octenidine-containing nasal gel on two different screening methods-antigen (Ag) detection based on colloidal gold immunochromatography and RT-PCR-in a prospective-type accuracy pilot study in asymptomatic SARS-CoV-2-positive inpatients. All patients still showed a positive test result after using the octenidine-containing nasal gel for about 3 days; therefore, its application did not influence SARS-CoV-2 screening, which is of high clinical relevance. Of note is that Ag detection was less sensitive, regardless of the presence of octenidine. From an infection prevention perspective, these results favor octenidine-based decolonization strategies, even during seasonal SARS-CoV-2 periods. As only asymptomatic patients are considered for elective interventions, screening programs based on RT-PCR technology should be preferred.

Improved detection of infection with SARS-CoV-2 Omicron variants of concern in healthcare workers by a second-generation rapid antigen test

IMPORTANCE

The results from this study demonstrate the usefulness of a second-generation rapid antigen test for early detection of infection with the SARS-CoV-2 Omicron variant of concern (VoC) and reveal a higher sensitivity to detect immune escape Omicron VoCs compared to a first-generation rapid antigen test (89.4% vs 83.7%) in the high-risk group of healthcare workers.

Establishment and application of national reference panels for SARS-CoV-2 antigen detection kit

To develop a national reference panel for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen detection kit and establish a quality standard. The cultures of SARS-CoV-2 and other pathogens were collected to establish a national reference panel for SARS-CoV-2 antigen detection. The stability and homogeneity of the reference panel were evaluated. Based on World Health Organization (WHO) guidance and nucleic acid quantitative results, a quality standard reference panel was established. Currently, three generations of SARS-CoV-2 antigen national reference materials with batch numbers 370095-202001, 370095-202202, and 370095-202203 have been successfully established. These national reference panels comprised 8 positive samples, 20 negative samples, 1 repetitive sample, and 1 lower detection limit sample. The stability and homogeneity of the reference panel meet the requirements. The quality standards are as follows: the positive and negative coincidence rates are 8/8 and 20/20, respectively. The 10 test results of the medium and low-concentration repetitive reference materials should be positive, and the color rendering should be uniform (or the coefficient of variance should not be higher than 20.0%). The lower detection limit should be at least 5 × 105 U/mL (equivalent to copies/mL), and higher concentrations above the lower detection limit must be positive. A national reference panel for the SARS-CoV-2 antigen detection kit has been established. As the standard of SARS-CoV-2 antigen reagents, the reference panel has played a crucial role in the pre-marketing quality evaluation and post-marketing quality supervision in China.

Serological methods for the detection of antibodies against monkeypox virus applicable for laboratories with different biosafety levels

The monkeypox virus (MPXV) outbreak in 2022 has renewed interest in the detection of antibodies against orthopox viruses (OPXV) and MPXV, as serological methods can aid diagnostics and are key to epidemiological studies. Here three complementary serological methods are described with different strengths to aid the development and evaluation of in-house assays: An immunofluorescence assay (IFA) for specific detection of IgG and IgM, an enzyme-linked immunosorbent assay for higher sample throughput to aid epidemiological studies and a neutralization test to detect virus neutralizing antibodies. As implementation of MPXV-specific diagnostics is often hampered by the requirement for a dedicated biosafety level 3 laboratory (BSL-3), the focus of this study is on biosafety aspects to facilitate safe testing also under BSL-2 conditions. To this aim, it was analyzed whether OPXV, which can be handled under BSL-2 conditions, could be used as less virulent alternatives to MPXV. Furthermore, an inactivation method was established to remove up to five log-steps of infectious virus particles from viraemic sera without compromising antibody detection. The results show that immunological cross-reactivity between OPXV provides an opportunity for the interchangeable usage of different OPXV species in serological assays, enabling MPXV serology outside of BSL-3 facilities.

Performance evaluation of SARS-CoV-2 antigen detection in the post-pandemic era: multi-laboratory assessment

OBJECTIVES

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen detection is an indispensable tool for epidemic surveillance in the post-pandemic era. Faced with irregular performance, a comprehensive external quality assessment (EQA) scheme was conducted by the National Center for Clinical Laboratories (NCCL) to evaluate the analytical performance and status of SARS-CoV-2 antigen tests.

METHODS

The EQA panel included ten lyophilized samples containing serial 5-fold dilutions of inactivated SARS-CoV-2-positive supernatants of the Omicron BA.1 and BA.5 strains and negative samples, which were classified into "validating" samples and "educational" samples. Data were analyzed according to qualitative results for each sample.

RESULTS

A total of 339 laboratories in China participated in this EQA scheme, and 378 effective results were collected. All validating samples were correctly reported by 90.56 % (307/339) of the participants and 90.21 % (341/378) of the datasets. The positive percent agreement (PPA) was >99 % for samples with concentrations of 2 × 107 copies/mL but was 92.20 % (697/756) for 4 × 106 copies/mL and 25.26 % (382/1,512) for 8 × 105 copies/mL samples. Colloidal gold was the most frequently used (84.66 %, 320/378) but showed the lowest PPAs (57.11 %, 1,462/2,560) for positive samples compared with fluorescence immunochromatography (90 %, 36/40) and latex chromatography (79.01 %, 335/424). Among 11 assays used in more than 10 clinical laboratories, ACON showed a higher sensitivity than other assays.

CONCLUSIONS

The EQA study can help to validate whether it's necessary to update antigen detection assays for manufacturers and provide participants with information about the performance of assays to take the first step toward routine post-market surveillance.

Clinical Evaluation and Comparison of Two Microfluidic Antigenic Assays for Detection of SARS-CoV-2 Virus

Given the ongoing pandemic, there is a need to identify SARS-CoV-2 and differentiate it from other respiratory viral infections in various critical settings. Since its introduction, rapid antigen testing is spreading worldwide, but diagnostic accuracy is extremely variable and often in disagreement with the manufacturer's specifications. Our study compared the clinical performances of two microfluidic rapid antigen tests towards a molecular assay, starting from positive samples. A total of 151 swabs collected at the Microbiology and Virology Laboratory of A.O. "SS Antonio e Biagio e C. Arrigo" (Alessandria, Italy) for the diagnosis of SARS-CoV-2 were simultaneously tested to evaluate accuracy, specificity, and agreement with the RT-qPCR results. Both assays showed an overall agreement of 100% for negative specimens, while positive accuracy comprised between 45.10% and 54.90%. According to the manufacturer's instructions, the greatest correlation between the antigenic and molecular assays was observed for the subset with high viral load (18/19, 94.74%), while it dramatically decreased for other subsets. Moreover, the ability to differentiate between SARS-CoV-2 and Flu provides an added value and could be addressed in an epidemic context. However, an in-house validation should be performed due to differences observed in performance declared by manufacturers and those actually obtained.

Structure and content of the EU-IVDR : Current status and implications for pathology

BACKGROUND

Regulation (EU) 2017/746 on in vitro diagnostic medical devices (IVDR) was passed by the European Parliament and the Council of the European Union on 5 April 2017 and came into force on 26 May 2017. A new amending regulation, which introduces a phased implementation of the IVDR with new transitional provisions for certain in vitro diagnostic medical devices (IVDs) and a later date of application of some requirements for in-house devices for healthcare facilities, was adopted on 15 December 2021. The combined use of CE-certified IVDs (CE-IVDs), in-house IVDs (IH-IVDs), and research use only (RUO) devices are a cornerstone of diagnostics in pathology departments and crucial for optimal patient care. The IVDR not only regulates the manufacture and placement on the market of industrially manufactured IVDs, but also imposes conditions on the manufacture and use of IH-IVDs for internal use by healthcare facilities.

OBJECTIVES

Our work provides an overview of the background and structure of the IVDR and identifies core areas that need to be interpreted and fleshed out in the context of the legal framework as well as expert knowledge.

CONCLUSIONS

The gaps and ambiguities in the IVDR crucially require the expertise of professional societies, alliances, and individual stakeholders to successfully facilitate the implementation and use of the IVDR in pathology departments and to avoid aberrant developments.

[Diagnostic performance of two antigen-tests compared to one PCR-Test to detect SARS-CoV-2 in an emergency department and emergency service]

BACKGROUND

In the German hospital landscape and emergency care the COVID-19 pandemic was a stress test. Emergency medical health care in Germany is ensured by the supply chain between prehospital emergency rescue and clinical emergency care in the emergency rooms. In hospitals and emergency care settings a rapid, simple, accurate, and cost-effective test is needed to identify SARS-CoV‑2. In the central emergency department it is important to strictly separate patients with suspected COVID-19 from non-infected emergency persons.

METHODS

Given the background mentioned above, the performance of antigen tests in the ambulance service of the city Jena and the central emergency department of the university hospital Jena was analysed and in addition verified by using the RT-PCR gold standard. Several multiple testing procedures were performed by using antigen tests in the ambulance service and the central emergency department, and by using one or both of these antigen tests followed by the RT-PCR test. A total of 980 patients were included in the study over a two-month period (October/November 2022).

RESULTS

The average age of all patients was 65 years. More than half of the actively treated patients came from the city of Jena. The sensitivity and specificity of the antigen tests were 66.7% and 99.2% in the clinical setting (the central emergency department) and 68.8% and 96.7% in the prehospital setting (in the ambulance service) compared to RT-PCR. In the prehospital setting the sensitivity of the antigen testing was slightly higher (2%) than the clinical antigen testing. Regarding the parallel testing, 6% of antigen tests had a false negative SARS-CoV‑2 antigen test result in the ambulance service and 4.6% of antigen tests had a false negative SARS-CoV‑2 antigen test result in the central emergency department. The false-negative antigen tests, and thus the potentially unrecognized individuals, were further reviewed by considering the Ct-value.

CONCLUSION

The use of antigen testing in the ambulance service and the emergency department can lead to a quick classification of COVID and non-COVID areas of an emergency department. The measurement accuracy of antigen testing in the ambulance service and central emergency department is not equivalent to the RT-PCR. Nevertheless, antigen testing is a useful initial screening tool for early detection of SARS-CoV‑2 in prehospital and clinical settings. Dual antigen testing may be useful for more accurate diagnosis of the SARS-CoV‑2 pathogen.

Rapid antigen tests for SARS-CoV-2-a synopsis of the medical evidence

SARS-CoV-2, the causative agent of the COVID-19 pandemic, continues to influence health, economy, and stability worldwide. Diagnostic testing for SARS-CoV-2 is important to contain the COVID-19 pandemic. With the commercial availability of certified antigen (Ag) rapid diagnostic tests (RDTs), which can be used to identify an infection with SARS-CoV-2 an easy-to-use tool was introduced. Self-tests can offer advantages to complement professionally administered rapid antigen detection or nucleic acid amplification testing (NAAT). Compared to real-time polymerase chain reaction (RT-PCR), Ag-RDTs are cost inexpensive, do not need specialized laboratory equipment, facilitating high-throughput testing. However, Ag-RDT sensitivities are strongly dependent on the viral load within the specimen, which has limited their application in clinical settings so far. The methodical limitations of Ag-RDTs may produce false negative test results, particularly when specimens with low viral loads are examined. This may facilitate viral transmissions if protective measurements are lifted mistakenly.

Ten rapid antigen tests for SARS-CoV-2 widely differ in their ability to detect Omicron-BA.4 and -BA.5

Since late 2021, the variant landscape of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been dominated by the variant of concern (VoC) Omicron and its sublineages. We and others have shown that the detection of Omicron-BA.1 and -BA.2-positive respiratory specimens by rapid antigen tests (RATs) is impaired compared to Delta VoC-containing samples. Here, in a single-center retrospective laboratory study, we evaluated the performance of ten most commonly used RATs for the detection of Omicron-BA.4 and -BA.5 infections. We used 171 respiratory swab specimens from SARS-CoV-2 RNA-positive patients, of which 71 were classified as BA.4 and 100 as BA.5. All swabs were collected between July and September 2022. 50 SARS-CoV-2 PCR-negative samples from healthy individuals, collected in October 2022, showed high specificity in 9 out of 10 RATs. When assessing analytical sensitivity using clinical specimens, the 50% limit of detection (LoD50) ranged from 7.6 × 104 to 3.3 × 106 RNA copies subjected to the RATs for BA.4 compared to 6.8 × 104 to 3.0 × 106 for BA.5. Overall, intra-assay differences for the detection of these two Omicron subvariants were not significant for both respiratory swabs and tissue culture-expanded virus isolates. In contrast, marked heterogeneity was observed among the ten RATs: to be positive in these point-of-care tests, up to 443-fold (BA.4) and up to 56-fold (BA.5) higher viral loads were required for the worst performing RAT compared to the best performing RAT. True-positive rates for Omicron-BA.4- or -BA.5-containing specimens in the highest viral load category (Ct values < 25) ranged from 94.3 to 34.3%, dropping to 25.6 to 0% for samples with intermediate Ct values (25-30). We conclude that the high heterogeneity in the performance of commonly used RATs remains a challenge for the general public to obtain reliable results in the evolving Omicron subvariant-driven pandemic.

Results of German external quality assessment schemes for SARS-CoV-2 antigen detection

The COVID-19 pandemic illustrated the important role of diagnostic tests, including lateral flow tests (LFTs), in identifying patients and their contacts to slow the spread of infections. INSTAND performed external quality assessments (EQA) for SARS-CoV-2 antigen detection with lyophilized and chemically inactivated cell culture supernatant of SARS-CoV-2 infected Vero cells. A pre-study demonstrated the suitability of the material. Participants reported qualitative and/or quantitative antigen results using either LFTs or automated immunoassays for five EQA samples per survey. 711 data sets were reported for LFT detection in three surveys in 2021. This evaluation focused on the analytical sensitivity of different LFTs and automated immunoassays. The inter-laboratory results showed at least 94% correct results for non-variant of concern (VOC) SARS-CoV-2 antigen detection for viral loads of ≥ 4.75 × 106 copies/mL and SARS-CoV-2 negative samples. Up to 85% had success for a non-VOC viral load of ~ 1.60 × 106 copies/mL. A viral load of ~ 1.42 × 107 copies/mL of the Delta VOC was reported positive in > 96% of results. A high specificity was found with almost 100% negative SARS-CoV-2 antigen results for HCoV 229E and HCoV NL63 positive samples. Quantitative results correlated with increasing SARS-CoV-2 viral load but showed a broad scatter. This study shows promising SARS-CoV-2 antigen test performance of the participating laboratories, but further investigations with the now predominant Omicron VOC are needed.

Evaluation of the diagnostic accuracy of two point-of-care tests for COVID-19 when used in symptomatic patients in community settings in the UK primary care COVID diagnostic accuracy platform trial (RAPTOR-C19)

BACKGROUND AND OBJECTIVE

Point-of-care lateral flow device antigen testing has been used extensively to identify individuals with active SARS-CoV-2 infection in the community. This study aimed to evaluate the diagnostic accuracy of two point-of-care tests (POCTs) for SARS-CoV-2 in routine community care.

METHODS

Adults and children with symptoms consistent with suspected current COVID-19 infection were prospectively recruited from 19 UK general practices and two COVID-19 testing centres between October 2020 and October 2021. Participants were tested by trained healthcare workers using at least one of two index POCTs (Roche-branded SD Biosensor Standard™ Q SARS-CoV-2 Rapid Antigen Test and/or BD Veritor™ System for Rapid Detection of SARS-CoV-2). The reference standard was laboratory triplex reverse transcription quantitative PCR (RT-PCR) using a combined nasal/oropharyngeal swab. Diagnostic accuracy parameters were estimated, with 95% confidence intervals (CIs), overall, in relation to RT-PCR cycle threshold and in pre-specified subgroups.

RESULTS

Of 663 participants included in the primary analysis, 39.2% (260/663, 95% CI 35.5% to 43.0%) had a positive RT-PCR result. The SD Biosensor POCT had sensitivity 84.0% (178/212, 78.3% to 88.6%) and specificity 98.5% (328/333, 96.5% to 99.5%), and the BD Veritor POCT had sensitivity 76.5% (127/166, 69.3% to 82.7%) and specificity 98.8% (249/252, 96.6% to 99.8%) compared with RT-PCR. Sensitivity of both devices dropped substantially at cycle thresholds ≥30 and in participants more than 7 days after onset of symptoms.

CONCLUSIONS

Both POCTs assessed exceed the Medicines and Healthcare products Regulatory Agency target product profile's minimum acceptable specificity of 95%. Confidence intervals for both tests include the minimum acceptable sensitivity of 80%. In symptomatic patients, negative results on these two POCTs do not preclude the possibility of infection. Tests should not be expected to reliably detect disease more than a week after symptom onset, when viral load may be reduced.

REGISTRATION

ISRCTN142269.

A coupled experimental and statistical approach for an assessment of SARS-CoV-2 infection risk at indoor event locations

Indoor event locations are particularly affected by the SARS-CoV-2 pandemic. At large venues, only incomplete risk assessments exist, whereby no suitable measures can be derived. In this study, a physical and data-driven statistical model for a comprehensive infection risk assessment has been developed. At venues displacement ventilation concepts are often implemented. Here simplified theoretical assumptions fail for the prediction of relevant airflows for airborne transmission processes. Thus, with locally resolving trace gas measurements infection risks are computed more detailed. Coupled with epidemiological data such as incidences, vaccination rates, test sensitivities, and audience characteristics such as masks and age distribution, predictions of new infections (mean), situational R-values (mean), and individual risks on- and off-seat can be achieved for the first time. Using the Stuttgart State Opera as an example, the functioning of the model and its plausibility are tested and a sensitivity analysis is performed with regard to masks and tests. Besides a reference scenario on 2022-11-29, a maximum safety scenario with an obligation of FFP2 masks and rapid antigen tests as well as a minimum safety scenario without masks and tests are investigated. For these scenarios the new infections (mean) are 10.6, 0.25 and 13.0, respectively. The situational R-values (mean) - number of new infections caused by a single infectious person in a certain situation - are 2.75, 0.32 and 3.39, respectively. Besides these results a clustered consideration divided by age, masks and whether infections occur on-seat or off-seat are presented. In conclusion this provides an instrument that can enable policymakers and operators to take appropriate measures to control pandemics despite ongoing mass gathering events.

SARS-CoV-2 Testing of Emergency Department Patients Using cobas® Liat® and eazyplex® Rapid Molecular Assays

Rapid testing for Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) of patients presenting to emergency departments (EDs) facilitates the decision for isolation on admission to hospital wards. Differences in the sensitivity of molecular assays have implications for diagnostic workflows. This study evaluated the performance of the cobas^® Liat^® RT-PCR, which is routinely used as the initial test for ED patients in our hospitals, compared with the eazyplex^® RT-LAMP. A total of 378 oropharyngeal and nasal swabs with positive Liat^® results were analysed. Residual sample aliquots were tested using NeuMoDx™, cobas^® RT-PCR, and the eazyplex^® assay. Patients were divided into asymptomatic (n = 157) and symptomatic (n = 221) groups according to the WHO case definition. Overall, 14% of positive Liat^® results were not confirmed by RT-PCR. These samples were mainly attributed to 26.8% of asymptomatic patients, compared to 3.8% of the symptomatic group. Therefore, positive Liat^® results were used to provisionally isolate patients in the ED until RT-PCR results were available. The eazyplex^® assay identified 62% and 90.6% of RT-PCR-confirmed cases in asymptomatic and symptomatic patients, respectively. False-negative eazyplex^® results were associated with RT-PCR Ct values > 30, and were more frequent in the asymptomatic group than in the symptomatic group (38.1% vs. 5.1%, respectively). Both the Liat^® and eazyplex^® assays are suitable for testing symptomatic patients. Their use in screening asymptomatic patients depends on the need to exclude any infection or identify those at high risk of transmission.

[The Diagnostic Test: Goodness, Characteristics, and Interpretation: Under the Impact of the Corona Pandemic and Different SARS-CoV-2 Tests]

INTRODUCTION

Many diagnostic tests are currently being performed around the world to detect SARS-CoV-2 infection. Positive and negative test results are not one hundred percent accurate, but have far-reaching consequences. There are false positives (test positive, uninfected) and false negatives (test negative, infected). A positive/negative result does not necessarily mean that the test subject is actually infected/non-infected. This article has two objectives: 1. to explain the most important characteristics of diagnostic tests with binary outcome 2. to point out problems and phenomena of interpretation of diagnostic tests, on the basis of different scenarios.

METHOD

Presentation of the basic concepts of the quality of a diagnostic test (sensitivity, specificity) and pre-test probability (prevalence of test group). Calculation (including formulas) of further important quantities.

RESULTS

In the basic scenario, sensitivity is 100%, specificity 98.8%, and pre-test probability of 1.0% (10 infected persons per 1,000 tested). For 1,000 diagnostic tests, the statistical mean is 22 positive cases, 10 of which are true-positive. The positive predictive probability is 45.7%. The prevalence calculated from this (22/1,000 tests) overestimates the actual prevalence (10/1,000 tests) by a factor of 2.2. All cases with a negative test outcome are true negative. The prevalence has a strong influence on the positive and negative predictive value. This phenomenon occurs even with otherwise very good test values of sensitivity and specificity. At a prevalence of only 5 infected persons per 10,000 (0.05%), the positive predictive probability drops to 4.0%. Lower specificity amplifies this effect, especially with small numbers of infected persons.

CONCLUSION

If the sensitivity or specificity is below 100%, diagnostic tests are always error-prone. If the prevalence of infected persons is low, a large number of false positive results are to be expected - even if the test is of good quality with a high sensitivity and especially a high specificity. This is accompanied by low positive predictive values, i. e. positive tested persons are not infected. A false positive test result in the first test can be clarified by carrying out a second test.

Facile and Unplugged Surface Plasmon Resonance Biosensor with NIR-Emitting Perovskite Nanocomposites for Fast Detection of SARS-CoV-2

The emergence of the coronavirus disease 2019 (COVID-19) pandemic prompted researchers to develop portable biosensing platforms, anticipating to detect the analyte in a label-free, direct, and simple manner, for deploying on site to prevent the spread of the infectious disease. Herein, we developed a facile wavelength-based SPR sensor built with the aid of a 3D printing technology and synthesized air-stable NIR-emitting perovskite nanocomposites as the light source. The simple synthesis processes for the perovskite quantum dots enabled low-cost and large-area production and good emission stability. The integration of the two technologies enabled the proposed SPR sensor to exhibit the characteristics of lightweight, compactness, and being without a plug, just fitting the requirements of on-site detection. Experimentally, the detection limit of the proposed NIR SPR biosensor for refractive index change reached the 10-6 RIU level, comparable with that of state-of-the-art portable SPR sensors. In addition, the bio-applicability of the platform was validated by incorporating a homemade high-affinity polyclonal antibody toward the SARS-CoV-2 spike protein. The results demonstrated that the proposed system was capable of discriminating between clinical swab samples collected from COVID-19 patients and healthy subjects because the used polyclonal antibody exhibited high specificity against SARS-CoV-2. Most importantly, the whole measurement process not only took less than 15 min but also needed no complex procedures or multiple reagents. We believe that the findings disclosed in this work can open an avenue in the field of on-site detection for highly pathogenic viruses.

A multi-country phase 2 study to evaluate the suitcase lab for rapid detection of SARS-CoV-2 in seven Sub-Saharan African countries: Lessons from the field

BACKGROUND

The COVID-19 pandemic led to severe health systems collapse, as well as logistics and supply delivery shortages across sectors. Delivery of PCR related healthcare supplies continue to be hindered. There is the need for a rapid and accessible SARS-CoV-2 molecular detection method in low resource settings.

OBJECTIVES

To validate a novel isothermal amplification method for rapid detection of SARS-CoV-2 across seven sub-Sharan African countries.

STUDY DESIGN

In this multi-country phase 2 diagnostic study, 3,231 clinical samples in seven African sites were tested with two reverse transcription Recombinase-Aided Amplification (RT-RAA) assays (based on SARS-CoV-2 Nucleocapsid (N) gene and RNA-dependent RNA polymerase (RdRP) gene). The test was performed in a mobile suitcase laboratory within 15 min. All results were compared to a real-time RT-PCR assay. Extraction kits based on silica gel or magnetic beads were applied.

RESULTS

Four sites demonstrated good to excellent agreement, while three sites showed fair to moderate results. The RdRP gene assay exhibited an overall PPV of 0.92 and a NPV of 0.88. The N gene assay exhibited an overall PPV of 0.93 and a NPV 0.88. The sensitivity of both RT-RAA assays varied depending on the sample Ct values. When comparing sensitivity between sites, values differed considerably. For high viral load samples, the RT-RAA assay sensitivity ranges were between 60.5 and 100% (RdRP assay) and 25 and 98.6 (N assay).

CONCLUSION

Overall, the RdRP based RT-RAA test showed the best assay accuracy. This study highlights the challenges of implementing rapid molecular assays in field conditions. Factors that are important for successful deployment across countries include the implementation of standardized operation procedures, in-person continuous training for staff, and enhanced quality control measures.

CoVSense: Ultrasensitive Nucleocapsid Antigen Immunosensor for Rapid Clinical Detection of Wildtype and Variant SARS-CoV-2

The widespread accessibility of commercial/clinically-viable electrochemical diagnostic systems for rapid quantification of viral proteins demands translational/preclinical investigations. Here, Covid-Sense (CoVSense) antigen testing platform; an all-in-one electrochemical nano-immunosensor for sample-to-result, self-validated, and accurate quantification of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N)-proteins in clinical examinations is developed. The platform's sensing strips benefit from a highly-sensitive, nanostructured surface, created through the incorporation of carboxyl-functionalized graphene nanosheets, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conductive polymers, enhancing the overall conductivity of the system. The nanoengineered surface chemistry allows for compatible direct assembly of bioreceptor molecules. CoVSense offers an inexpensive (<$2 kit) and fast/digital response (<10 min), measured using a customized hand-held reader (<$25), enabling data-driven outbreak management. The sensor shows 95% clinical sensitivity and 100% specificity (Ct<25), and overall sensitivity of 91% for combined symptomatic/asymptomatic cohort with wildtype SARS-CoV-2 or B.1.1.7 variant (N = 105, nasal/throat samples). The sensor correlates the N-protein levels to viral load, detecting high Ct values of ≈35, with no sample preparation steps, while outperforming the commercial rapid antigen tests. The current translational technology fills the gap in the workflow of rapid, point-of-care, and accurate diagnosis of COVID-19.

Performance of 20 rapid antigen detection tests to detect SARS-CoV-2 B.1.617.2 (Delta) and B.1.1.529 (Omicron) variants using a clinical specimen panel from January 2022, Berlin, Germany

BackgroundThere are conflicting reports on the performance of rapid antigen detection tests (RDT) in the detection of the SARS-CoV-2 Omicron (B.1.1.529) variant; however, these tests continue to be used frequently to detect potentially contagious individuals with high viral loads.AimThe aim of this study was to investigate comparative detection of the Delta (B.1.617.2) and Omicron variants by using a selection of 20 RDT and a limited panel of pooled combined oro- and nasopharyngeal clinical Delta and Omicron specimens.MethodsWe tested 20 CE-marked RDT for their performance to detect SARS-CoV-2 Delta and Omicron by using a panel of pooled clinical specimens collected in January 2022 in Berlin, Germany.ResultsWe observed equivalent detection performance for Delta and Omicron for most RDT, and sensitivity was widely in line with our previous pre-Delta/Omicron evaluation. Some variation for individual RDT was observed either for Delta vs Omicron detection, or when compared with the previous evaluation, which may be explained both by different panel sizes resulting in different data robustness and potential limitation of batch-to-batch consistency. Additional experiments with three RDT using non-pooled routine clinical samples confirmed comparable performance to detect Delta vs Omicron. Overall, RDT that were previously positively evaluated retained good performance also for Delta and Omicron variants.ConclusionOur findings suggest that currently available RDT are sufficient for the detection of SARS-CoV-2 Delta and Omicron variants.

Direct-to-consumer laboratory testing (DTCT): challenges and implications for specialists in laboratory medicine

In vitro diagnostics (IVD) testing is a powerful tool for medical diagnosis, and patients' safety is guaranteed by a complex system of personnel qualification of the specialist in laboratory medicine, of process control, and legal restrictions in healthcare, most of them under national regulation. Direct-to-consumer laboratory testing (DTCT) is testing ordered by the consumer and performed either by the consumer at home or analysis of self-collected samples in a laboratory. However, since DTCT are not always subject to effective competent authority oversight, DTCT may pose risks to lay persons using and relying on it for healthcare decision-making. Laboratory medicine specialists should be very cautious when new DTCTs are introduced. As qualified professionals, they should feel obliged to warn and educate patients and the public about the risks of inappropriate and harmful DTCT.

Clinical Evaluation of an Antigen Home Test Using Surface-Enhanced Raman Spectroscopy and Stacking Pad for SARS-CoV-2 Screening with Nasal and Salivary Swab Samples

This prospective study aimed to evaluate the performance of the InstaView COVID-19 (coronavirus diseases 2019) Antigen Home Test (InstaView AHT) which detects severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens. In this test kit, surface-enhanced Raman spectroscopy was used, a stacking pad was inserted, and nasal swab and salivary swab samples were used simultaneously to improve performance. The clinical performance of the InstaView AHT was compared to that of RT-PCR using nasopharyngeal samples. The participants without any prior training were recruited and performed the sample collection, testing, and interpretation of the results by themselves. Of the 91 PCR-positive patients, 85 had positive InstaView AHT results. The sensitivity and specificity of the InstaView AHT were 93.4% (95% confidence interval [CI]: 86.2-97.5) and 99.4% (95% CI: 98.2-99.9). The sensitivity of the InstaView AHT was above 90% for all samples obtained from patients with Ct ≤ 20, 20 < Ct ≤ 25, and 25 < Ct ≤ 30 (100%, 95.1%, and 92.0%, respectively). The InstaView AHT can be used as an alternative to RT-PCR testing because of its relatively high sensitivity and specificity, especially when SARS-CoV-2 prevalence is high, and the availability of RT-PCR testing is limited.

Evaluation of Four Rapid Antigen Tests for the Detection of SARS-CoV-2 Infection with Nasopharyngeal Swabs

Owing to the high transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, the capacity of testing systems based on the gold standard real-time reverse transcription–polymerase chain reaction (rRT-PCR) is limited. Rapid antigen tests (RATs) can substantially contribute to the prevention of community transmission, but their further assessment is required. Here, using 1503 nasopharyngeal swabs, we compared the diagnostic performance of four RAT kits (Abbott Panbio™ COVID-19 Ag Rapid Test, SD Biosensor Standard™ Q COVID-19 Ag Test, Humasis COVID-19 Ag Test, and SG Medical Acrosis COVID-19 Ag Test) to the cycle threshold (Ct) values obtained from rRT-PCR. The precision values, area under the curve values, SARS-CoV-2 variant detection ability, and non-SARS-CoV-2 specificity of all four kits were similar. An assay using the Acrosis kit had a significantly better positive detection rate with a higher recall value and cut-off value than that using the other three RAT kits. During the current COVID-19 pandemic, the Acrosis kit is an effective tool to prevent the spread of SARS-CoV-2 in communities.

Analysis of seven SARS-CoV-2 rapid antigen tests in detecting omicron (B.1.1.529) versus delta (B.1.617.2) using cell culture supernatants and clinical specimens

PURPOSE

Omicron is rapidly spreading as a new SARS-CoV-2 variant of concern (VOC). The question whether this new variant has an impact on SARS-CoV-2 rapid antigen test (RAT) performance is of utmost importance. To obtain an initial estimate regarding differences of RATs in detecting omicron and delta, seven commonly used SARS-CoV-2 RATs from different manufacturers were analysed using cell culture supernatants and clinical specimens.

METHODS

For this purpose, cell culture-expanded omicron and delta preparations were serially diluted in Dulbecco's modified Eagle's Medium (DMEM) and the Limit of Detection (LoD) for both VOCs was determined. Additionally, clinical specimens stored in viral transport media or saline (n = 51) were investigated to complement in vitro results with cell culture supernatants. Ct values and RNA concentrations were determined via quantitative reverse transcription polymerase chain reaction (RT-qPCR).

RESULTS

The in vitro determination of the LoD showed no obvious differences in detection of omicron and delta for the RATs examined. The LoD in this study was at a dilution level of 1:1,000 (corresponding to 3.0-5.6 × 106 RNA copies/mL) for tests I-V and at a dilution level of 1:100 (corresponding to 3.7-4.9 × 107 RNA copies/mL) for tests VI and VII. Based on clinical specimens, no obvious differences were observed between RAT positivity rates when comparing omicron to delta in this study setting. Overall positivity rates varied between manufacturers with 30-81% for omicron and 42-71% for delta. Test VII was only conducted in vitro with cell culture supernatants for feasibility reasons. In the range of Ct < 23, positivity rates were 50-100% for omicron and 67-93% for delta.

CONCLUSION

In this study, RATs from various manufacturers were investigated, which displayed no obvious differences in terms of analytical LoD in vitro and RAT positivity rates based on clinical samples comparing the VOCs omicron and delta. However, differences between tests produced by various manufacturers were detected. In terms of clinical samples, a focus of this study was on specimens with high virus concentrations. Further systematic, clinical and laboratory studies utilizing large datasets are urgently needed to confirm reliable performance in terms of sensitivity and specificity for all individual RATs and SARS-CoV-2 variants.

Variable detection of Omicron-BA.1 and -BA.2 by SARS-CoV-2 rapid antigen tests

During 2022, the COVID-19 pandemic has been dominated by the variant of concern (VoC) Omicron (B.1.1.529) and its rapidly emerging subvariants, including Omicron-BA.1 and -BA.2. Rapid antigen tests (RATs) are part of national testing strategies to identify SARS-CoV-2 infections on site in a community setting or to support layman's diagnostics at home. We and others have recently demonstrated an impaired RAT detection of infections caused by Omicron-BA.1 compared to Delta. Here, we evaluated the performance of five SARS-CoV-2 RATs in a single-centre laboratory study examining a total of 140 SARS-CoV-2 PCR-positive respiratory swab samples, 70 Omicron-BA.1 and 70 Omicron-BA.2, as well as 52 SARS-CoV-2 PCR-negative swabs collected from March 8th until April 10th, 2022. One test did not meet minimal criteria for specificity. In an assessment of the analytical sensitivity in clinical specimen, the 50% limit of detection (LoD50) ranged from 4.2 × 104 to 9.2 × 105 RNA copies subjected to the RAT for Omicron-BA.1 compared to 1.3 × 105 to 1.5 × 106 for Omicron-BA.2. Overall, intra-assay differences for the detection of Omicron-BA.1-containing and Omicron-BA.2-containing samples were non-significant, while a marked overall heterogeneity among the five RATs was observed. To score positive in these point-of-care tests, up to 22-fold (LoD50) or 68-fold (LoD95) higher viral loads were required for the worst performing compared to the best performing RAT. The rates of true-positive test results for these Omicron subvariant-containing samples in the highest viral load category (Ct values < 25) ranged between 44.7 and 91.1%, while they dropped to 8.7 to 22.7% for samples with intermediate Ct values (25-30). In light of recent reports on the emergence of two novel Omicron-BA.2 subvariants, Omicron-BA.2.75 and BJ.1, awareness must be increased for the overall reduced detection rate and marked differences in RAT performance for these Omicron subvariants.

Virus variant-specific clinical performance of SARS coronavirus two rapid antigen tests in point-of-care use, from November 2020 to January 2022

OBJECTIVES

Antigen rapid diagnostic tests (RDTs) for SARS coronavirus 2 (SARS-CoV-2) are quick, widely available, and inexpensive. Consequently, RDTs have been established as an alternative and additional diagnostic strategy to quantitative reverse transcription polymerase chain reaction (RT-qPCR). However, reliable clinical and large-scale performance data specific to a SARS-CoV-2 virus variant of concern (VOC) are limited, especially for the Omicron VOC. The aim of this study was to compare RDT performance among different VOCs.

METHODS

This single-centre prospective performance assessment compared RDTs from three manufacturers (NADAL, Panbio, MEDsan) with RT-qPCR including deduced standardized viral load from oropharyngeal swabs for detection of SARS-CoV-2 in a clinical point-of-care setting from November 2020 to January 2022.

RESULTS

Among 35 479 RDT/RT-qPCR tandems taken from 26 940 individuals, 164 of the 426 SARS-CoV-2 positive samples tested true positive with an RDT corresponding to an RDT sensitivity of 38.50% (95% CI, 34.00-43.20%), with an overall specificity of 99.67% (95% CI, 99.60-99.72%). RDT sensitivity depended on viral load, with decreasing sensitivity accompanied by descending viral load. VOC-dependent sensitivity assessment showed a sensitivity of 42.86% (95% CI, 32.82-53.52%) for the wild-type SARS-CoV-2, 43.42% (95% CI, 32.86-54.61%) for the Alpha VOC, 37.67% (95% CI, 30.22-45.75%) for the Delta VOC, and 33.67% (95% CI, 25.09-43.49%) for the Omicron VOC. Sensitivity in samples with high viral loads of ≥106 SARS-CoV-2 RNA copies per mL was significantly lower in the Omicron VOC (50.00%; 95% CI, 36.12-63.88%) than in the wild-type SARS-CoV-2 (79.31%; 95% CI, 61.61-90.15%; p 0.015).

DISCUSSION

RDT sensitivity for detection of the Omicron VOC is reduced in individuals infected with a high viral load, which curtails the effectiveness of RDTs. This aspect furthert: limits the use of RDTs, although RDTs are still an irreplaceable diagnostic tool for rapid, economic point-of-care and extensive SARS-CoV-2 screening.

[Use of and Attitudes toward Tests for the Detection of SARS-CoV-2 and Corresponding Antibodies: Results of a Nationally Representative Survey in Late Summer 2021]

OBJECTIVE

There is a lack of knowledge regarding utilization of and attitudes towards tests for the detection of SARS-CoV-2 in Germany. Our work aimed to reduce this gap.

METHODS

Data were taken from a nationally representative online survey (August 24th to 3rd September 2021, n=3,075; mean age: 44.5 years). Utilization of and attitudes toward Covid-19-tests were quantified in detail.

RESULTS

In sum, 79.1% of respondents had already undergone an appropriate test to detect SARS-CoV-2 test (mainly rapid antigen testing at rapid testing centers and self-testing) or an antibody test. With the exception of a PCR test, Covid-19 tests were rarely perceived as uncomfortable. Respondents were most likely to prefer a rapid antigen test in a rapid testing center. The main reasons for using self-testing as well as rapid antigen testing at rapid testing centers were (i) protection of others, (ii) for their own health precautions, and (iii) traveling. The main reasons for not using self-testing/rapid antigen testing at the workplace/training center were: (i) already vaccinated against Covid-19/recovered from Covid-19, followed by (ii) the home office workplace, and (iii) a lack of perceived benefit. Nearly 80% were somewhat or very satisfied, with access to testing at the workplace/training center and rapid testing centers.

CONCLUSION

Our work described the use of and aspects of attitudes toward tests for the detection of SARS-CoV-2 in Germany in late summer 2021. At that time, such test offers were already used quite often and were predominantly perceived as not being very unpleasant. The protection of other individuals was one of the main reasons for the use of such tests. Future research in this area is desirable (e. g., among the oldest old and in times when free-of-charge testing is no longer offered).

What is the prevalence of COVID-19 detection by PCR among deceased individuals in Lusaka, Zambia? A postmortem surveillance study

OBJECTIVES

To determine the prevalence of COVID-19 postmortem setting in Lusaka, Zambia.

DESIGN

A systematic, postmortem prevalence study.

SETTING

A busy, inner-city morgue in Lusaka.

PARTICIPANTS

We sampled a random subset of all decedents who transited the University Teaching Hospital morgue. We sampled the posterior nasopharynx of decedents using quantitative PCR. Prevalence was weighted to account for age-specific enrolment strategies.

INTERVENTIONS

Not applicable-this was an observational study.

PRIMARY OUTCOMES

Prevalence of COVID-19 detections by PCR. Results were stratified by setting (facility vs community deaths), age, demographics and geography and time.

SECONDARY OUTCOMES

Shifts in viral variants; causal inferences based on cycle threshold values and other features; antemortem testing rates.

RESULTS

From 1118 decedents enrolled between January and June 2021, COVID-19 was detected among 32.0% (358/1116). Roughly four COVID-19+ community deaths occurred for every facility death. Antemortem testing occurred for 52.6% (302/574) of facility deaths but only 1.8% (10/544) of community deaths and overall, only ~10% of COVID-19+ deaths were identified in life. During peak transmission periods, COVID-19 was detected in ~90% of all deaths. We observed three waves of transmission that peaked in July 2020, January 2021 and ~June 2021: the AE.1 lineage and the Beta and Delta variants, respectively. PCR signals were strongest among those whose deaths were deemed 'probably due to COVID-19', and weakest among children, with an age-dependent increase in PCR signal intensity.

CONCLUSIONS

COVID-19 was common among deceased individuals in Lusaka. Antemortem testing was rarely done, and almost never for community deaths. Suspicion that COVID-19 was the cause of deaths was highest for those with a respiratory syndrome and lowest for individuals <19 years.

A brief review on the validation of biology methods for COVID-19 detection

The COVID-19 global pandemic has been going on for more than two years, and the evolution of SARS-CoV-2 with many variants of concern still poses a risk to public health. Sufficient access to qualified and validated testing plays an important role in detecting and alerting trends of the pandemic and provides evidence for making decisions in preventive strategies and policies. Depending on the method of testing and laboratory conditions, validation parameters (i.e., analytical sensitivity, limit of detection, diagnostic sensitivity, analytical specificity, diagnostic specificity, repeatability, reproducibility, robustness, positive predictive value, negative predictive value, applicability, practicability, and time to results) can be very different. With three main types of COVID-19 detection kits available, comprising nucleic acid, serological, and antigen detection, the kind of validation parameters that should be used becomes a complicated consideration and takes time to assess. Our review provides valuable and comprehensive information for laboratories in the assessment and selection of the optimal parameters to validate new COVID-19 test kits.

Canine real-time detection of SARS-CoV-2 infections in the context of a mass screening event

Introduction

Previous research demonstrated that medical scent detection dogs have the ability to distinguish SARS-CoV-2 positive from negative samples with high diagnostic accuracy. To deploy these dogs as a reliable screening method, it is mandatory to examine if canines maintain their high diagnostic accuracy in real-life screening settings. We conducted a study to evaluate the performance of medical scent detection dogs under real-life circumstances.

Methods

Eight dogs were trained to detect SARS-CoV-2 RT-qPCR-positive samples. Four concerts with a total of 2802 participants were held to evaluate canines’ performance in screening individuals for SARS-CoV-2 infection. Sweat samples were taken from all participants and presented in a line-up setting. In addition, every participant had been tested with a SARS-CoV-2 specific rapid antigen test and a RT-qPCR and they provided information regarding age, sex, vaccination status and medical disease history. The participants’ infection status was unknown at the time of canine testing. Safety measures such as mask wearing and distance keeping were ensured.

Results

The SARS-CoV-2 detection dogs achieved a diagnostic specificity of 99.93% (95% CI 99.74% to 99.99%) and a sensitivity of 81.58% (95% CI 66.58% to 90.78%), respectively. The overall rate of concordant results was 99.68%. The majority of the study population was vaccinated with varying vaccines and vaccination schemes, while several participants had chronic diseases and were under chronic medication. This did not influence dogs’ decisions.

Conclusion

Our results demonstrate that SARS-CoV-2 scent detection dogs achieved high diagnostic accuracy in a real-life scenario. The vaccination status, previous SARS-CoV-2 infection, chronic disease and medication of the participants did not influence the performance of the dogs in detecting the acute infection. This indicates that dogs provide a fast and reliable screening option for public events in which high-throughput screening is required.

Head-to-head comparison of the accuracy of saliva and nasal rapid antigen SARS-CoV-2 self-testing: cross-sectional study

BACKGROUND

The diagnostic accuracy of unsupervised self-testing with rapid antigen diagnostic tests (Ag-RDTs) is mostly unknown. We studied the diagnostic accuracy of a self-performed SARS-CoV-2 saliva and nasal Ag-RDT in the general population.

METHODS

This large cross-sectional study consecutively included unselected individuals aged ≥ 16 years presenting for SARS-CoV-2 testing at three public health service test sites. Participants underwent molecular test sampling and received two self-tests (the Hangzhou AllTest Biotech saliva self-test and the SD Biosensor nasal self-test by Roche Diagnostics) to perform themselves at home. Diagnostic accuracy of both self-tests was assessed with molecular testing as reference.

RESULTS

Out of 2819 participants, 6.5% had a positive molecular test. Overall sensitivities were 46.7% (39.3-54.2%) for the saliva Ag-RDT and 68.9% (61.6-75.6%) for the nasal Ag-RDT. With a viral load cut-off (≥ 5.2 log10 SARS-CoV-2 E-gene copies/mL) as a proxy of infectiousness, these sensitivities increased to 54.9% (46.4-63.3%) and 83.9% (76.9-89.5%), respectively. For the nasal Ag-RDT, sensitivities were 78.5% (71.1-84.8%) and 22.6% (9.6-41.1%) in those symptomatic and asymptomatic at the time of sampling, which increased to 90.4% (83.8-94.9%) and 38.9% (17.3-64.3%) after applying the viral load cut-off. In those with and without prior SARS-CoV-2 infection, sensitivities were 36.8% (16.3-61.6%) and 72.7% (65.1-79.4%). Specificities were > 99% and > 99%, positive predictive values > 70% and > 90%, and negative predictive values > 95% and > 95%, for the saliva and nasal Ag-RDT, respectively, in most analyses. Most participants considered the self-performing and result interpretation (very) easy for both self-tests.

CONCLUSIONS

The Hangzhou AllTest Biotech saliva self Ag-RDT is not reliable for SARS-CoV-2 detection, overall, and in all studied subgroups. The SD Biosensor nasal self Ag-RDT had high sensitivity in individuals with symptoms and in those without prior SARS-CoV-2 infection but low sensitivity in asymptomatic individuals and those with a prior SARS-CoV-2 infection which warrants further investigation.

Point-of-care detection of SARS-CoV-2 antigen among symptomatic vs. asymptomatic persons: Testing for COVID-19 vs. infectivity

Background

Management of the coronavirus disease 2019 (COVID-19) pandemic caused by a novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) requires rapid and simple methods to detect COVID-19 patients and identify potential infectors. This study aimed to evaluate the utility of a point-of-care (PoC) rapid antigen diagnostic test (Ag-RDT) in these settings.

Patients and methods

Individuals who consecutively presented for SARS-CoV-2 testing at a tertiary care center in Buenos Aires, Argentina, underwent PoC Ag-RDT testing and real-time RT-PCR (qRT-PCR) on the same day during June 2021.

Results

Of 584 included subjects, 108 (18.5%) were symptomatic for COVID-19 while the remaining presented for miscellaneous reasons unrelated to possible or confirmed contact with a SARS-CoV-2-infected individual. A positive Ag-RDT result was obtained in 26 (24.1%) symptomatic and 7 (1.5%) asymptomatic persons (p < 0.001), which was concordant with qRT-PCR in 105/108 [97.2%, Cohen's kappa coefficient (κ) = 0.927] symptomatic and 467/476 (98.1% κ = 0.563) asymptomatic participants, with a positive percentage agreement (PPA; 95% confidence interval) of 89.7% (71.5-97.3%) and 42.9% (18.8-70.4%), respectively. None of the 11 false-negative diagnoses showed a C_t-value ≤20. Considering only failures with a C_t-value below 31 as hypothetical infectivity threshold of 10⁵ SARS-CoV-2 RNA copies/mL, concordance was observed in 98.1% (κ = 0.746) in the asymptomatic population, accounting for a PPA of 66.7% (30.9-91%).

Conclusions

PoC Ag-RDT accurately detected active SARS-CoV-2 infection and showed acceptable diagnostic performance in asymptomatic persons potentially spreading infectious virus. Ag-RDT may therefore be useful to slow down or stop transmission by enabling adequate decisions on isolation at a public health level.

[Development of specific guidance for the safe opening and operation of recreational destinations under pandemic conditions]

Background

The SARS-CoV‑2 pandemic led to the closure of leisure and recreation facilities worldwide. As part of a model study funded by the Baden-Wuerttemberg Ministry of Social Affairs, Health and Integration, it was possible to demonstrate how a hygiene and safety concept can be successfully implemented in practice using the example of the opening and operation of an amusement park in Baden-Wuerttemberg (Germany) under scientific supervision.

Objective

The aim of the model project was, besides the verification of a possible infection event through a visit to the amusement park, to develop and review a recommended course of action for the safe opening and operation of leisure facilities under pandemic conditions, which can be transferred to other destinations.

Methods

A variety of data sources were used for this project: Recurrent expert rounds of multidisciplinary teams (business administration, healthcare research, sociology and medicine), aerosol measurement data, observation protocols, official infection statistics and interview data from visitor surveys.

Results

The action plan developed in this project provides guidance and recommendations for operators of recreation and leisure facilities to implement measures that enhance staff and guest safety, allowing facilities to operate under pandemic conditions.

Conclusion

This study sets a precedent using the example of a recreational park in Baden-Wuerttemberg (Germany) to serve as a guide for other facilities; however, operations in the leisure and tourism sector are unique and measures are accordingly difficult to transfer directly. The recommended action plan is further intended to support policy makers in future pandemic situations regarding measures to close, open and operate such facilities.

Diagnostic accuracy of rapid point-of-care tests for diagnosis of current SARS-CoV-2 infections in children: a systematic review and meta-analysis

OBJECTIVE

To systematically assess the diagnostic accuracy of rapid point-of-care tests for diagnosis of current SARS-CoV-2 infections in children under real-life conditions.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

MEDLINE, Embase, Cochrane Database for Systematic Reviews, INAHTA HTA database, preprint servers (via Europe PMC), ClinicalTrials.gov, WHO ICTRP from 1 January 2020 to 7 May 2021; NICE Evidence Search, NICE Guidance, FIND Website from 1 January 2020 to 24 May 2021.

REVIEW METHODS

Diagnostic cross-sectional or cohort studies were eligible for inclusion if they had paediatric study participants and compared rapid point-of care tests for diagnosing current SARS-CoV-2 infections with reverse transcription polymerase chain reaction (RT-PCR) as the reference standard. The Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool was used to assess the risk of bias and the applicability of the included studies. Bivariate meta-analyses with random effects were performed. Variability was assessed by subgroup analyses.

RESULTS

17 studies with a total of 6355 paediatric study participants were included. All studies compared antigen tests against RT-PCR. Overall, studies evaluated eight antigen tests from six different brands. Only one study was at low risk of bias. The pooled overall diagnostic sensitivity and specificity in paediatric populations was 64.2% (95% CI 57.4% to 70.5%) and 99.1% (95% CI 98.2% to 99.5%), respectively. In symptomatic children, the pooled diagnostic sensitivity was 71.8% (95% CI 63.6% to 78.8%) and the pooled diagnostic specificity was 98.7% (95% CI 96.6% to 99.5%). The pooled diagnostic sensitivity in asymptomatic children was 56.2% (95% CI 47.6% to 64.4%) and the pooled diagnostic specificity was 98.6% (95% CI 97.3% to 99.3%).

CONCLUSIONS

The performance of current antigen tests in paediatric populations under real-life conditions varies broadly. Relevant data were only identified for very few antigen tests on the market, and the risk of bias was mostly unclear due to poor reporting. Additionally, the most common uses of these tests in children (eg, self-testing in schools or parents testing their toddlers before kindergarten) have not been addressed in clinical performance studies yet. The observed low diagnostic sensitivity may impact the planned purpose of the broad implementation of testing programmes.

PROSPERO REGISTRATION NUMBER

CRD42021236313.

Potential Use of Exhaled Breath Condensate for Diagnosis of SARS-CoV-2 Infections: A Systematic Review and Meta-Analysis

Background. Reverse-transcriptase polymerase chain reaction (RT-qPCR) assays performed on respiratory samples collected through nasal swabs still represent the gold standard for COVID-19 diagnosis. Alternative methods to this invasive and time-consuming options are still being inquired, including the collection of airways lining fluids through exhaled breath condensate (EBC). Materials and Methods. We performed a systematic review and meta-analysis in order to explore the reliability of EBC as a way to collect respiratory specimens for RT-qPCR for diagnosis of COVID-19. Results. A total of 4 studies (205 specimens), were ultimately collected, with a pooled sensitivity of 69.5% (95%CI 26.8–93.4), and a pooled specificity of 98.3% (95%CI 87.8–99.8), associated with high heterogeneity and scarce diagnostic agreement with the gold standard represented by nasal swabs (Cohen’s kappa = 0.585). Discussion. Even though non-invasive options for diagnosis of COVID-19 are still necessary, EBC-based RT-qPCR showed scarce diagnostic performances, ultimately impairing its implementation in real-world settings. However, as few studies have been carried out to date, and the studies included in the present review are characterized by low numbers and low sample power, further research are requested to fully characterize the actual reliability of EBC-based RT-qPCR in the diagnosis of COVID-19.

[Structure and content of the EU-IVDR : Current status and implications for pathology]

BACKGROUND

Regulation (EU) 2017/746 on in vitro diagnostic medical devices (IVDR) was passed by the European Parliament and the Council of the European Union on 5 April 2017 and came into force on 26 May 2017. A new amending regulation, which introduces a phased implementation of the IVDR with new transitional provisions for certain in vitro diagnostic medical devices and a later date of application of some requirements for in-house devices for healthcare facilities, was adopted on 15 December 2021. The combined use of CE-IVDs, in-house IVDs, and RUO products are a cornerstone of diagnostics in pathology departments and crucial for optimal patient care. The IVDR not only regulates the manufacture and placement on the market of industrially manufactured IVDs, but also imposes conditions on the manufacture and use of IH-IVDs for internal use by healthcare facilities.

OBJECTIVES

Our work provides an overview of the background and structure of the IVDR and identifies core areas that need to be interpreted and fleshed out in the context of the legal framework as well as expert knowledge.

CONCLUSIONS

The gaps and ambiguities in the IVDR crucially require the expertise of professional societies, alliances, and individual stakeholders to successfully facilitate the implementation and use of the IVDR in pathology departments and to avoid aberrant developments.