Showing papers on "Rapid diagnostic test published in 2021"

Performance and operational feasibility of antigen and antibody rapid diagnostic tests for COVID-19 in symptomatic and asymptomatic patients in Cameroon: a clinical, prospective, diagnostic accuracy study.

Abstract: Summary Background Real-time PCR is recommended to detect SARS-CoV-2 infection. However, PCR availability is restricted in most countries. Rapid diagnostic tests are considered acceptable alternatives, but data are lacking on their performance. We assessed the performance of four antibody-based rapid diagnostic tests and one antigen-based rapid diagnostic test for detecting SARS-CoV-2 infection in the community in Cameroon. Methods In this clinical, prospective, diagnostic accuracy study, we enrolled individuals aged at least 21 years who were either symptomatic and suspected of having COVID-19 or asymptomatic and presented for screening. We tested peripheral blood for SARS-CoV-2 antibodies using the Innovita (Biological Technology; Beijing, China), Wondfo (Guangzhou Wondfo Biotech; Guangzhou, China), SD Biosensor (SD Biosensor; Gyeonggi-do, South Korea), and Runkun tests (Runkun Pharmaceutical; Hunan, China), and nasopharyngeal swabs for SARS-CoV-2 antigen using the SD Biosensor test. Antigen rapid diagnostic tests were compared with Abbott PCR testing (Abbott; Abbott Park, IL, USA), and antibody rapid diagnostic tests were compared with Biomerieux immunoassays (Biomerieux; Marcy l'Etoile, France). We retrospectively tested two diagnostic algorithms that incorporated rapid diagnostic tests for symptomatic and asymptomatic patients using simulation modelling. Findings 1195 participants were enrolled in the study. 347 (29%) tested SARS-CoV-2 PCR-positive, 223 (19%) rapid diagnostic test antigen-positive, and 478 (40%) rapid diagnostic test antibody-positive. Antigen-based rapid diagnostic test sensitivity was 80·0% (95% CI 71·0–88·0) in the first 7 days after symptom onset, but antibody-based rapid diagnostic tests had only 26·8% sensitivity (18·3–36·8). Antibody rapid diagnostic test sensitivity increased to 76·4% (70·1–82·0) 14 days after symptom onset. Among asymptomatic participants, the sensitivity of antigen-based and antibody-based rapid diagnostic tests were 37·0% (27·0–48·0) and 50·7% (42·2–59·1), respectively. Cohen's κ showed substantial agreement between Wondfo antibody rapid diagnostic test and gold-standard ELISA (κ=0·76; sensitivity 0·98) and between Biosensor and ELISA (κ=0·60; sensitivity 0·94). Innovita (κ=0·47; sensitivity 0·93) and Runkun (κ=0·43; sensitivity 0·76) showed moderate agreement. An antigen-based retrospective algorithm applied to symptomatic patients showed 94·0% sensitivity and 91·0% specificity in the first 7 days after symptom onset. For asymptomatic participants, the algorithm showed a sensitivity of 34% (95% CI 23·0–44·0) and a specificity of 92·0% (88·0–96·0). Interpretation Rapid diagnostic tests had good overall sensitivity for diagnosing SARS-CoV-2 infection. Rapid diagnostic tests could be incorporated into efficient testing algorithms as an alternative to PCR to decrease diagnostic delays and onward viral transmission. Funding Medecins Sans Frontieres WACA and Medecins Sans Frontieres OCG. Translations For the French and Spanish translations of the abstract see Supplementary Materials section.

Point-of-care COVID-19 diagnostics powered by lateral flow assay.

Abstract: Since its first discovery in December 2019, the global coronavirus disease 2019 (COVID-19) pandemic caused by the novel coronavirus (SARS-CoV-2) has been posing a serious threat to human life and health. Diagnostic testing is critical for the control and management of the COVID-19 pandemic. In particular, diagnostic testing at the point of care (POC) has been widely accepted as part of the post restriction COVID-19 control strategy. Lateral flow assay (LFA) is a popular POC diagnostic platform that plays an important role in controlling the COVID-19 pandemic in industrialized countries and resource-limited settings. Numerous pioneering studies on the design and development of diverse LFA-based diagnostic technologies for the rapid diagnosis of COVID-19 have been done and reported by researchers. Hundreds of LFA-based diagnostic prototypes have sprung up, some of which have been developed into commercial test kits for the rapid diagnosis of COVID-19. In this review, we summarize the crucial role of rapid diagnostic tests using LFA in targeting SARS-CoV-2-specific RNA, antibodies, antigens, and whole virus. Then, we discuss the design principle and working mechanisms of these available LFA methods, emphasizing their clinical diagnostic efficiency. Ultimately, we elaborate the challenges of current LFA diagnostics for COVID-19 and highlight the need for continuous improvement in rapid diagnostic tests.

The Abbott PanBio WHO emergency use listed, rapid, antigen-detecting point-of-care diagnostic test for SARS-CoV-2—Evaluation of the accuracy and ease-of-use

Abstract: OBJECTIVES: Diagnostics are essential for controlling the pandemic. Identifying a reliable and fast diagnostic device is needed for effective testing. We assessed performance and ease-of-use of the Abbott PanBio antigen-detecting rapid diagnostic test (Ag-RDT). METHODS: This prospective, multi-centre diagnostic accuracy study enrolled at two sites in Germany. Following routine testing with reverse-transcriptase polymerase chain reaction (RT-PCR), a second study-exclusive swab was performed for Ag-RDT testing. Routine swabs were nasopharyngeal (NP) or combined NP/oropharyngeal (OP) whereas the study-exclusive swabs were NP. To evaluate performance, sensitivity and specificity were assessed overall and in predefined sub-analyses accordingly to cycle-threshold values, days after symptom onset, disease severity and study site. Additionally, an ease-of-use assessment (EoU) and System Usability Scale (SUS) were performed. RESULTS: 1108 participants were enrolled between Sept 28 and Oct 30, 2020. Of these, 106 (9.6%) were PCR-positive. The Abbott PanBio detected 92/106 PCR-positive participants with a sensitivity of 86.8% (95% CI: 79.0% - 92.0%) and a specificity of 99.9% (95% CI: 99.4%-100%). The sub-analyses indicated that sensitivity was 95.8% in Ct-values <25 and within the first seven days from symptom onset. The test was characterized as easy to use (SUS: 86/100) and considered suitable for point-of-care settings. CONCLUSION: The Abbott PanBio Ag-RDT performs well for SARS-CoV-2 testing in this large manufacturer independent study, confirming its WHO recommendation for Emergency Use in settings with limited resources.

Performance characteristics of five antigen-detecting rapid diagnostic test (Ag-RDT) for SARS-CoV-2 asymptomatic infection: a head-to-head benchmark comparison

Abstract: Background Mass testing for early identification and isolation of infectious COVID-19 individuals, irrespective of concurrent symptoms, is an efficacious strategy to reduce disease transmission. Antigen-detecting rapid diagnostic tests (Ag-RDT) appear as a potentially suitable tool for mass testing on account of their ease-of-use, fast turnaround time, and low cost. However, benchmark comparisons are scarce, particularly in the context of unexposed asymptomatic individuals. Methods We used nasopharyngeal specimens from unexposed asymptomatic individuals to assess five Ag-RDTs: PanBio™ COVID-19 Ag Rapid test (Abbott), CLINITEST® Rapid COVID-19 Antigen Test (Siemens), SARS-CoV-2 Rapid Antigen Test (Roche Diagnostics), SARS-CoV-2 Antigen Rapid Test Kit (Lepu Medical), and COVID-19 Coronavirus Rapid Antigen Test Cassette (Surescreen). Samples were collected between December 2020-January 2021 during the third wave of the epidemic in Spain. Findings The analysis included 101 specimens with confirmed positive PCR results and 185 with negative PCR. For the overall sample, the performance parameters of Ag-RDTs were as follows: Abbott assay, sensitivity 38·6% (95% CI 29·1–48·8) and specificity 99·5% (97–100%); Siemens, sensitivity 51·5% (41·3–61·6) and specificity 98·4% (95·3–99·6); Roche, sensitivity 43·6% (33·7–53·8) and specificity 96·2% (92·4–98·5); Lepu, sensitivity 45·5% (35·6–55·8) and specificity 89·2% (83·8–93·3%); Surescreen, sensitivity 28·8% (20·2–38·6) and specificity 97·8% (94·5–99·4%). For specimens with cycle threshold (Ct) 99% and a PPV Interpretation Two commercial, widely available assays can be used for SARS-CoV-2 antigen testing to achieve sensitivity in specimens with a Ct Funding Blueberry diagnostics, Fundacio Institut d’Investigacio en Ciencies de la Salut Germans Trias i Pujol, and #YoMeCorono.org crowdfunding campaign. Research in context Evidence before this study In December 2020, we searched on PubMed for articles containing the terms “antigen”, “test” (or Ag-RDT), and “SARS-CoV-2” or “COVID-19” either in the title or the abstract. Our search yielded 79 entries corresponding to articles written in English. Of them, 33 were articles presenting the diagnostic performance of qualitative lateral-flow antigen-detecting rapid diagnostic tests (Ag-RDT). Four of these articles reported the results of head-to-head comparisons of various Ag-RDTs; in all cases, the number of tests was lower than the recommended for retrospective assessments of diagnostic performance (i.e., minimum of 100 PCR positive and 100 PCR negative). Furthermore, all head-to-head comparisons found in the literature included specimens obtained among individuals with varying disease status (none of which asymptomatic), thus limiting the adequacy of the estimates for an asymptomatic screening strategy. Added value of this study We compared for the first time head-to-head five Ag-RDT using a powered set of fresh respiratory specimens PCR-confirmed positive or negative, collected from unexposed asymptomatic individuals during screening campaigns for early detection of SARS-CoV-2 infection. The sample size was large enough to draw robust conclusions. Our analysis identified four Ag-RDTs (i.e., assays marketed by Abbott, Siemens, Roche, and Surescreen) with specificity higher than 96%. Despite the low sensitivity for the overall sample (range 29% to 51%), the corresponding values for the subset of samples with Ct 99% for all tests, while the PPV would be Implications of all the available evidence Current data on the diagnostic performance of Ag-RDTs is heterogeneous and precludes benchmark assessments. Furthermore, the screening of asymptomatic populations is currently not considered among the intended uses of Ag-RDT, mostly because of lack of evidence on test performance in samples from unexposed asymptomatic individuals. Our findings add to the current evidence in two ways: first, we provide benchmarking data on Ag-RDTs, assessed head-to-head in a single set of respiratory specimens; second, we provide data on the diagnostic performance of Ag-RDTs in unexposed asymptomatic individuals. Our findings support the idea that Ag-RDTs can be used for mass screening in low prevalence settings and accurately rule out a highly infectious case in such setting.

Using artificial intelligence to improve COVID-19 rapid diagnostic test result interpretation.

Abstract: Serological rapid diagnostic tests (RDTs) are widely used across pathologies, often providing users a simple, binary result (positive or negative) in as little as 5 to 20 min. Since the beginning of the COVID-19 pandemic, new RDTs for identifying SARS-CoV-2 have rapidly proliferated. However, these seemingly easy-to-read tests can be highly subjective, and interpretations of the visible "bands" of color that appear (or not) in a test window may vary between users, test models, and brands. We developed and evaluated the accuracy/performance of a smartphone application (xRCovid) that uses machine learning to classify SARS-CoV-2 serological RDT results and reduce reading ambiguities. Across 11 COVID-19 RDT models, the app yielded 99.3% precision compared to reading by eye. Using the app replaces the uncertainty from visual RDT interpretation with a smaller uncertainty of the image classifier, thereby increasing confidence of clinicians and laboratory staff when using RDTs, and creating opportunities for patient self-testing.

Surveillance of Acute SARS-CoV-2 Infections in School Children and Point-Prevalence During a Time of High Community Transmission in Switzerland

Abstract: Background: Switzerland had one of the highest incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Europe during the second wave. Schools were open as in most of Europe with specific preventive measures in place. However, the frequency and transmission of acute unrecognized, asymptomatic or oligosymptomatic infections in schools during this time of high community transmission is unknown. Thereof, our aim was to pilot a surveillance system that detects acute SARS-CoV-2 infections in schools and possible transmission within classes. Methods: Fourteen out of the randomly selected sample of the Ciao Corona cohort study participated between December 1 and 11, a time when incidence rate for SARS-CoV-2 infections was high for the canton of Zurich. We determined point-prevalence of acute SARS-CoV-2 infections of school children attending primary and secondary school. A buccal swab for polymerase chain reaction (PCR) and a rapid diagnostic test (RDT) to detect SARS-CoV-2 were taken twice 1 week apart (T1 and T2) in a cohort of children from randomly selected classes. A questionnaire assessed demographics and symptoms compatible with a SARS-CoV-2 infection during the past 5 days. Results: Out of 1,299 invited children, 641 (49%) 6- to 16-year-old children and 66 teachers from 14 schools and 67 classes participated in at least one of two testings. None of the teachers but one child had a positive PCR at T1, corresponding to a point-prevalence in children of 0.2% (95% CI 0.0-1.1%), and no positive PCR was detected at T2. The child with positive PCR at T1 was negative on the RDT at T1 and both tests were negative at T2. There were 7 (0.6%) false positive RDTs in children and 2 (1.7%) false positive RDTs in teachers at T1 or T2 among 5 schools (overall prevalence 0.7%). All 9 initially positive RDTs were negative in a new buccal sample taken 2 h to 2 days later, also confirmed by PCR. Thirty-five percent of children and 8% of teachers reported mild symptoms during the 5 days prior to testing. Conclusion: In a setting of high incidence of SARS-CoV-2 infections, unrecognized virus spread within schools was very low. Schools appear to be safe with the protective measures in place (e.g., clearly symptomatic children have to stay at home, prompt contact tracing with individual and class-level quarantine, and structured infection prevention measures in school). Specificity of the RDT was within the lower boundary of performance and needs further evaluation for its use in schools. Given the low point prevalence even in a setting of very high incidence, a targeted test, track, isolate and quarantine (TTIQ) strategy for symptomatic children and school personnel adapted to school settings is likely more suitable approach than surveillance on entire classes and schools. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT04448717, ClinicalTrials.gov NCT04448717.

Evaluation of a SARS-CoV-2 antigen-detecting rapid diagnostic test as a self-test: Diagnostic performance and usability.

Abstract: To control the spread of the coronavirus disease 2019 (COVID-19) epidemics, it is necessary to have easy-to-use, reliable diagnostic tests available. The nasopharyngeal sampling method being often uncomfortable, nasal sampling could prove to be a viable alternative to the reference sampling method. We performed a multicentre, prospective validation study of the COVID-VIRO® test, using a nasal swab sampling method, in a point-of-care setting. In addition, we performed a multicentre, prospective, and usability study to validate the use of the rapid antigen nasal diagnostic test by laypersons. In March 2021, 239 asymptomatic and symptomatic patients were included in the validation study. Compared with reverse-transcription polymerase chain reaction on nasopharyngeal samples, the sensitivity and specificity of the COVID-VIRO® Antigen test combined with a nasal sampling method were evaluated as 96.88% and 100%, respectively. A total of 101 individuals were included in the usability study. Among these, 99% of the participants rated the instructions material as good, 98% of the subjects executed the test procedure well, and 98% of the participants were able to correctly interpret the test results. This study validates the relevance of COVID-VIRO® as a diagnostic tool from nasal specimens as well as its usability in the general population. COVID-VIRO® diagnostic performances and ease of use make it suitable for widespread utilization.

Utility of Antigen-Based Rapid Diagnostic Test for Detection of SARS-CoV-2 Virus in Routine Hospital Settings

Abstract: OBJECTIVE: This study aims to evaluate the performance of an antigen-based rapid diagnostic test (RDT) for the detection of the SARS-CoV-2 virus. METHODS: A cross-sectional study was conducted on 677 patients. Two nasopharyngeal swabs and 1 oropharyngeal swab were collected from patients. The RDT was performed onsite by a commercially available immune-chromatographic assay on the nasopharyngeal swab. The nasopharyngeal and oropharyngeal swabs were examined for SARS-CoV-2 RNA by real-time reverse-transcription quantitative polymerase chain reaction (RT-qPCR) assay. RESULTS: The overall sensitivity of the SARS-CoV-2 RDT was 34.5% and the specificity was 99.8%. The positive predictive value and negative predictive value of the test were 96.6% and 91.5%, respectively. The detection rate of RDT in RT-qPCR positive results was high (45%) for cycle threshold values <25. CONCLUSION: The utility of RDT is in diagnosing symptomatic patients and may not be particularly suited as a screening tool for patients with low viral load. The low sensitivity of RDT does not qualify its use as a single test in patients who test negative; RT-qPCR continues to be the gold standard test.

Clinical application of rapid diagnostic test kit for SARS-CoV-2 antibodies into the field of patient care.

Abstract: Clinical applicability of rapid diagnostic test kit for SARS-CoV-2 antibodies was evaluated. The kit detected antibodies from day 9-56 of illness. IgG bands were observed up to 1: 1000 dilutions. The kit could detect 90.5% of IgG and 61.9% of IgM antibodies of mild febrile patients without pneumonia.

Choosing interventions to eliminate forest malaria: preliminary results of two operational research studies inside Cambodian forests.

Abstract: Rapid elimination of Plasmodium falciparum malaria in Cambodia is a goal with both national and international significance. Transmission of malaria in Cambodia is limited to forest environments, and the main population at risk consists of forest-goers who rely on forest products for income or sustenance. The ideal interventions to eliminate malaria from this population are unknown. In two forested regions of Cambodia, forest-goers were trained to become forest malaria workers (FMWs). In one region, FMWs performed mass screening and treatment, focal screening and treatment, and passive case detection inside the forest. In the other region, FMWs played an observational role for the first year, to inform the choice of intervention for the second year. In both forests, FMWs collected blood samples and questionnaire data from all forest-goers they encountered. Mosquito collections were performed in each forest. Malaria prevalence by PCR was high in the forest, with 2.3–5.0% positive for P. falciparum and 14.6–25.0% positive for Plasmodium vivax among forest-goers in each study site. In vectors, malaria prevalence ranged from 2.1% to 9.6%, but no P. falciparum was observed. Results showed poor performance of mass screening and treatment, with sensitivity of rapid diagnostic tests equal to 9.1% (95% CI 1.1%, 29.2%) for P. falciparum and 4.4% (95% CI 1.6%, 9.2%) for P. vivax. Malaria infections were observed in all demographics and throughout the studied forests, with no clear risk factors emerging. Malaria prevalence remains high among Cambodian forest-goers, but performance of rapid diagnostic tests is poor. More adapted strategies to this population, such as intermittent preventive treatment of forest goers, should be considered.

Frontline Screening for SARS-CoV-2 Infection at Emergency Department Admission by Third Generation Rapid Antigen Test: Can We Spare RT-qPCR?

Abstract: To complement RT-qPCR testing for diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, many countries have introduced the use of rapid antigen tests. As they generally display lower real-life performances than expected, their correct positioning as frontline screening is still controversial. Despite the lack of data from daily clinical use, third generation microfluidic assays (such as the LumiraDx SARS-CoV-2 Ag test) have recently been suggested to have similar performances to RT-qPCR and have been proposed as alternative diagnostic tools. By analyzing 960 nasopharyngeal swabs from 960 subjects at the emergency department admissions of a tertiary COVID-19 hospital, LumiraDx assay demonstrated a specificity of 97% (95% CI: 96-98), and a sensitivity of 85% (95% CI: 82-89) in comparison with RT-qPCR, which increases to 91% (95% CI: 86-95) for samples with a cycle threshold ≤ 29. Fifty false-negative LumiraDx-results were confirmed by direct quantification of genomic SARS-CoV-2 RNA through droplet-digital PCR (median (IQR) load = 5880 (1657-41,440) copies/mL). Subgenomic N and E RNAs were detected in 52% (n = 26) and 56% (n = 28) of them, respectively, supporting the presence of active viral replication. Overall, the LumiraDx test complies with the minimum performance requirements of the WHO. Yet, the risk of a misrecognition of patients with active COVID-19 persists, and the need for confirmatory RT-qPCR should not be amended.

Machine Learning based Malaria Prediction using Clinical Findings

Abstract: Even today, Malaria is the most deadly disease in Asia and sub-Saharan Africa and particularly in Senegal. This is mainly due to inadequate medical care support with frequent late and error-diagnoses by medical professionals. Besides, mostly used diagnostic standards such as the rapid diagnostic test is not fully reliable. With the development and widespread acceptance of automated systems in the healthcare system, machine learning algorithms can support medical professionals in their decision-making procedure. An experimental analysis of different machine learning techniques to predict Malaria is proposed in this work. These techniques attempt to determine whether or not a patient suffersfrom Malaria using various clinical findings like signs and symptoms. The algorithms’ efficiency has been thoroughly validated and analysed over two actual data sets of malaria patients’ taken from Senegal. The results obtained show that Random Forest, Support Vector Machine with Gaussian Kernel and Artificial Neural Networks are promising and offer the best overall accuracy to predict the appearance or not of the disease with precision, recall and F1-score at least equal to 92%, 85% and 89% respectively on both datasets on which they outperform the Rapid Diagnostic Test.

SARS-CoV-2 Serological testing in frontline health workers in Zimbabwe.

Abstract: BACKGROUND: In order to protect health workers from SARS-CoV-2, there is need to characterise the different types of patient facing health workers Our first aim was to determine both the infection status and seroprevalence of SARS-CoV-2 in health workers Our second aim was to evaluate the occupational and demographic predictors of seropositivity to inform the country's infection prevention and control (IPC) strategy METHODS AND PRINCIPAL FINDINGS: We invited 713 staff members at 24 out of 35 health facilities in the City of Bulawayo in Zimbabwe Compliance to testing was defined as the willingness to uptake COVID-19 testing by answering a questionnaire and providing samples for both antibody testing and PCR testing SARS-COV-2 antibodies were detected using a rapid diagnostic test kit and SAR-COV-2 infection was determined by real-time (RT)-PCR Of the 713 participants, 635(89%) consented to answering the questionnaire and providing blood sample for antibody testing while 560 (785%) agreed to provide nasopharyngeal swabs for the PCR SARS-CoV-2 testing Of the 635 people (aged 18-73) providing a blood sample 391% reported a history of past COVID-19 symptoms while 142% reported having current symptoms of COVID-19 The most-prevalent co-morbidity among this group was hypertension (220%) followed by asthma (70%) and diabetes (60%) The SARS-CoV-2 sero-prevalence was 89% Of the 560 participants tested for SARS-CoV-2 infection, 2 participants (036%) were positive for SAR-CoV-2 infection by PCR testing None of the SARS-CoV-2 antibody positive people were positive for SAR-CoV-2 infection by PCR testing CONCLUSION AND INTERPRETATION: In addition to clinical staff, several patient-facing health workers were characterised within Zimbabwe's health system and the seroprevalence data indicated that previous exposure to SAR-CoV-2 had occurred across the full spectrum of patient-facing staff with nurses and nurse aides having the highest seroprevalence Our results highlight the need for including the various health workers in IPC strategies in health centres to ensure effective biosecurity and biosafety

Evaluation of two rapid antigenic tests for the detection of sars-cov-2 in nasopharyngeal swabs

Abstract: (1) Background: In the current context of the COVID-19 crisis, there is a need for fast, easy-to-use, and sensitive diagnostic tools in addition to molecular methods. We have therefore decided to evaluate the performance of newly available antigen detection kits in “real-life” laboratory conditions. (2) Methods: The sensitivity and specificity of two rapid diagnostic tests (RDT)—the COVID-19 Ag Respi-Strip from Coris Bioconcept, Belgium (CoRDT), and the coronavirus antigen rapid test cassette from Healgen Scientific, LLC, USA (HeRDT)—were evaluated on 193 nasopharyngeal samples using RT-PCR as the gold standard. (3) Results: The sensitivity obtained for HeRDT was 88% for all collected samples and 91.1% for samples with Ct ≤ 31. For the CoRDT test, the sensitivity obtained was 62% for all collected samples and 68.9% for samples with Ct ≤ 31. (4) Conclusions: Despite the excellent specificity obtained for both kits, the poor sensitivity of the CoRDT did not allow for its use in the rapid diagnosis of COVID-19. HeRDT satisfied the World Health Organization’s performance criteria for rapid antigen detection tests. Its high sensitivity, quick response, and ease of use allowed for the implementation of HeRDT at the laboratory of the University Hospital of Liege.

Prevalence of Immunoglobulin G (IgG) Against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Evaluation of a Rapid MEDsan IgG Test in Children Seeking Medical Care.

Abstract: In a sample of 208 children seeking medical care, seropositivity rate of anti-SARS-CoV-2 IgG antibodies was 8.7%, suggesting a similar infection rate to that observed in adults, but >100-fold the incidence of RT-PCR-confirmed pediatric cases. Compared to the gold-standard combined ELISA+immunofluorescence, the MEDsan IgG rapid diagnostic test performed accurately.

Laboratory and Field Evaluation of the Crystal VC-O1 Cholera Rapid Diagnostic Test.

Abstract: Cholera is a severe acute, highly transmissible diarrheal disease which affects many low- and middle-income countries. Outbreaks of cholera are confirmed using microbiological culture, and additional cases during the outbreak are generally identified based on clinical case definitions, rather than laboratory confirmation. Many low-resource areas where cholera occurs lack the capacity to perform culture in an expeditious manner. A simple, reliable, and low-cost rapid diagnostic test (RDT) would improve identification of cases allowing rapid response to outbreaks. Several commercial RDTs are available for cholera testing with two lines to detect either serotypes O1 and O139; however, issues with sensitivity and specificity have not been optimal with these bivalent tests. Here, we report an evaluation of a new commercially available cholera dipstick test which detects only serotype O1. In both laboratory and field studies in Kenya, we demonstrate high sensitivity (97.5%), specificity (100%), and positive predictive value (100%) of this new RDT targeting only serogroup O1. This is the first field evaluation for the new Crystal VC-O1 RDT; however, with these high-performance metrics, this RDT could significantly improve cholera outbreak detection and improve surveillance for better understanding of cholera disease burden.

The Design and Evaluation of a Mobile System for Rapid Diagnostic Test Interpretation

Abstract: Rapid diagnostic tests (RDTs) provide point-of-care medical screening without the need for expensive laboratory equipment RDTs are theoretically straightforward to use, yet their analog colorimetric output leaves room for diagnostic uncertainty and error Furthermore, RDT results within a community are kept isolated unless they are aggregated by healthcare workers, limiting the potential that RDTs can have in supporting public health efforts In light of these issues, we present a system called RDTScan for detecting and interpreting lateral flow RDTs with a smartphone RDTScan provides real-time guidance for clear RDT image capture and automatic interpretation for accurate diagnostic decisions RDTScan is structured to be quickly configurable to new RDT designs by requiring only a template image and some metadata about how the RDT is supposed to be read, making it easier to extend than a data-driven approach Through a controlled lab study, we demonstrate that RDTScan's limit-of-detection can match, and even exceed, the performance of expert readers who are interpreting the physical RDTs themselves We then present two field evaluations of smartphone apps built on the RDTScan system: (1) at-home influenza testing in Australia and (2) malaria testing by community healthcare workers in Kenya RDTScan achieved 975% and 963% accuracy compared to RDT interpretation by experts in the Australia Flu Study and the Kenya Malaria Study, respectively

Assessment of ASHA for knowledge, diagnosis and treatment on malaria in Mandla district of Madhya Pradesh as part of the malaria elimination demonstration project

Abstract: The role of Accredited Social Health Activist (ASHA) in the health care delivery services at the periphery level is crucial for achieving disease prevention, control and elimination goals The objective of the study was to assess the knowledge, attitude, practices, priorities and capability of ASHA related to malaria diagnosis and treatment as part of the Malaria Elimination Demonstration Project in 1233 villages of district Mandla, Madhya Pradesh A cross sectional study was conducted using a fully structured, pre-tested interview schedule during June and July 2017 (before the field operations of MEDP were started) Two hundred twenty (17%) of the total ASHAs were selected for the interview from the 9 developmental blocks of Mandla district Knowledge, Attitude and Practices (KAP) study revealed that most ASHAs knew that mosquitoes are the main agent for spread of malaria (977%) They mostly used Rapid Diagnostic Test (RDT) for diagnosis (918%) The majority (873%) correctly identified negative RDT result while only 15% and 105%, respectively, identified Plasmodium vivax and Plasmodium falciparum positive cases correctly Further analysis showed that 85% ASHAs used chloroquine, 445% used artemisinin-based combination therapy (ACT), and 555% used primaquine for treatment of malaria It was also found that only 382% ASHA gave PQ for 14 days in cases of P vivax At the time of the interview, 191% ASHAs did not have any RDTs for diagnosis and 477% reported not having ACT for treatment of P falciparum malaria This study has revealed that ASHAs in the test district were not adequately trained or stocked for malaria parasite species identification and treatment, which are the major components of malaria elimination programme This study has, therefore, revealed a need for training ASHAs on testing by RDT and proper treatment regimen for P vivax and P falciparum

A SARS-CoV-2 antigen rapid diagnostic test for resource limited settings.

Abstract: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative agent of COVID-19 disease. RT-qPCR has been the primary method of diagnosis; however, the required infrastructure is lacking in many developing countries and the virus has remained a global challenge. More inexpensive and immediate test methods are required to facilitate local, regional, and national management strategies to re-open world economies. Here we have developed a SARS-CoV-2 antigen test in an inexpensive lateral flow format to generate a chromatographic result identifying the presence of the SARS-CoV-2 antigen, and thus an active infection, within a patient anterior nares swab sample. Our 15-min test requires no equipment or laboratory infrastructure to administer with a limit of detection of 2.0 × 102 TCID50/mL and 87.5% sensitivity, 100% specificity when tested against 40 known positive and 40 known negative patient samples established by a validated RT-qPCR test.

Sustained Malaria Transmission despite Reactive Screen-and-Treat in a Low-Transmission Area of Southern Zambia.

Abstract: Malaria elimination strategies are designed to more effectively identify and treat infected individuals to interrupt transmission. One strategy, reactive screen-and-treat, starts with passive detection of symptomatic cases at health facilities. Individuals residing within the index case and neighboring households are screened with a malaria rapid diagnostic test (RDT) and treated if positive. However, it is unclear to what extent this strategy is effective in reducing transmission. Reactive screen-and-treat was implemented in Choma district, Southern Province, Zambia, in 2013, in which residents of the index case and neighboring households within 140 m were screened with an RDT. From March 2016 to July 2018, the screening radius was extended to 250-m, and additional follow-up visits at 30 and 90 days were added to evaluate the strategy. Plasmodium falciparum parasite prevalence was measured using an RDT and by quantitative PCR (qPCR). A 24-single nucleotide polymorphism molecular bar-code assay was used to genotype parasites. Eighty-four index case households with 676 residents were enrolled between March 2016 and March 2018. Within each season, parasite prevalence declined significantly in index households at the 30-day visit and remained low at the 90-day visit. However, parasite prevalence was not reduced to zero. Infections identified by qPCR persisted between study visits and were not identified by RDT. Parasites identified within the same household were most genetically related; however, overall parasite relatedness was low and similar across time and space. Thus, despite implementation of a reactive screen-and-treat program, parasitemia was not eliminated, and persisted in targeted households for at least 3 months.

Ultrasensitive Diagnostics for Low-Density Asymptomatic Plasmodium falciparum Infections in Low-Transmission Settings.

Abstract: The emergence of multidrug-resistant Plasmodium falciparum malaria in Southeast Asia (SEA) has accelerated regional malaria elimination efforts. Most malaria in this and other low-transmission settings exists in asymptomatic individuals, which conventional diagnostic tests lack the sensitivity to detect. This has led to the development of new ultrasensitive diagnostics that are capable of detecting these low-parasitemia infections. This review summarizes the current status of ultrasensitive technologies, including PCR and loop-mediated isothermal amplification (LAMP)-based methods, as well as a newly developed ultrasensitive rapid diagnostic test (uRDT). The sensitivity, specificity, and field performance of these platforms will be examined, as well as their suitability for use in resource-limited settings to aid in malaria elimination efforts. uRDTs, with their improved sensitivity, are now able to detect approximately half of asymptomatic infections, providing a useful point-of-contact tool for malaria surveillance. The increased sensitivity and high-throughput nature of PCR-based tests make them ideal for screening large populations in places where laboratory capacity exists, and the recent commercialization of malaria LAMP kits should facilitate their adoption as a public health tool in places where such infrastructure is lacking. Finally, recent advances with dried blood spots may enable utilization of the extensive laboratory infrastructure of higher-income countries to assist with molecular surveillance in support of malaria elimination. If malaria is to be eliminated in SEA and other low-endemicity regions, then ultrasensitive diagnostics will likely play a key role in identifying and clearing the vast asymptomatic pool of infections that are common to these regions.

School-based screening and treatment may reduce P. falciparum transmission.

Abstract: In areas where malaria remains entrenched, novel transmission-reducing interventions are essential for malaria elimination. We report the impact screening-and-treatment of asymptomatic Malawian schoolchildren (n = 364 in the rainy season and 341 in the dry season) had on gametocyte—the parasite stage responsible for human-to-mosquito transmission—carriage. We used concomitant household-based surveys to predict the potential reduction in transmission in the surrounding community. Among 253 students with P. falciparum infections at screening, 179 (71%) had infections containing gametocytes detected by Pfs25 qRT-PCR. 84% of gametocyte-containing infections were detected by malaria rapid diagnostic test. While the gametocyte prevalence remained constant in untreated children, treatment with artemether-lumefantrine reduced the gametocyte prevalence (p < 0.0001) from 51.8 to 9.7% and geometric mean gametocyte density (p = 0.008) from 0.52 to 0.05 gametocytes/microliter. In community surveys, 46% of all gametocyte-containing infections were in school-age children, who comprised only 35% of the population. Based on these estimates six weeks after the intervention, the gametocyte burden in the community could be reduced by 25–55% depending on the season and the measure used to characterize gametocyte carriage. Thus, school-based interventions to treat asymptomatic infections may be a high-yield approach to not only improve the health of schoolchildren, but also decrease malaria transmission.