Rapid Detection Test Research Articles

Hepatitis B and human immunodeficiency virus infections within correctional facilities in Ghana.

Previous studies have suggested high Immunodeficiency Virus (HIV) and hepatitis B virus (HBV) prevalence in prisons in Ghana. However, this study was part of a nationally representative bio-behavioural survey and determined the prevalence of HIV and HBV among prison inmates and identified factors associated with these infections. Both biomedical and behavioural data were collected from a total of 2,443 prison inmates from 19 prison stations during 2013 in Ghana; 12 male prisons and 7 female prisons selected across the country. The national HIV screening algorithm was used for HIV testing while two rapid detection tests were used to confirm HBV infections. HIV and HBV prevalence among prisoners in Ghana were approximately 2.34% and 12.38% respectively. Only 5 inmates, had co-infection with both viruses. The prevalence of HIV was significantly lower among male inmates (1.5%) compared to the female inmates (11.8%). Age, sex, and marital status, were significantly associated with both HIV and HBV infections. However, BMI category, IDU, and time spent in prison were associated with HIV infections. The educational level was significantly associated with HBV infections. After binary logistic regression, being female (AOR: 0.18, 95% CI: 0.07-0.45, p<0.001) and having a stay of 5 years or more (AOR: 0.07, 95% CI: 0.01-0.60, p = 0.016), increased the risk of having HIV infection. While, those with no formal education (AOR: 0.65, 95% CI: 0.45-0.95, p = 0.024) and are underweight (AOR: 0.51, 95% CI: 0.27-0.99, p = 0.046), were more likely to have HBV infection. Forced penetrative sex may be a problem in the prisons. The need to have and strengthen an integrated screening, treatment and vaccination plan for the prison is emphasized. The prison does not serve as an exceptionally high risk to the general population. The findings support a critical look at the issue of forced penetrative sex in the prisons.

Evaluation of Immulex S. pneumoniae Omni test for the direct detection of S. pneumoniae from positive blood cultures

Rapid and early identification of Streptococcus pneumoniae from positive blood cultures is crucial for the management of patients with bloodstream infections (BSI). Many identification systems in microbiology laboratories have difficulty differentiating S. pneumoniae from other closely related species in the Streptococcus mitis group. To overcome this limitation, we developed a rapid workflow in our laboratory combining direct MALDI-TOF MS identification with the Immulex S. pneumoniae Omni test (SSI Diagnostica, Denmark) for rapid detection of S. pneumoniae directly from positive blood cultures. The workflow was evaluated using 51 Streptococcus isolates. Compared to conventional biochemical testing, our new workflow demonstrates 100 % specificity and sensitivity for the detection and differentiation of S. pneumoniae from other closely related species. Our new workflow is accurate, cost-effective, and can easily be implemented in microbiology laboratories that already perform direct MALDI-TOF identification from positive blood cultures to improve the management of patients with invasive pneumococcal disease. ImportanceInvasive pneumococcal disease remains a major public health problem worldwide. Reducing the time to identify Streptococcus pneumoniae in positive blood cultures allows patients to be treated sooner with more targeted and effective antibiotics. We evaluated a two-step protocol where positive blood cultures are first tested directly by MALDI-TOF MS and any samples containing Streptococcus species are tested by Immulex S. pneumoniae Omni test to both detect and differentiate S. pneumoniae from other closely related Streptococcus species. Our study results showed 100 % sensitivity and specificity, and a much faster turn-around time than conventional methods.

Handheld Ultra-Fast Duplex Polymerase Chain Reaction Assays and Lateral Flow Detection and Identification of Leishmania Parasites for Cutaneous Leishmaniases Diagnosis.

Early and accurate detection of infectious diseases is a key step for surveillance, epidemiology and control, notably timely disease diagnosis, patient management and follow-up. In this study, we aimed to develop handheld ultra-fast duplex PCR assays coupled to amplicon detection by lateral flow (LF) immunoassay to deliver a rapid and simple molecular diagnostic test for concomitant detection and identification of the main Leishmania parasites encountered in Tunisia. We selected two DNA targets to amplify L. major/L. tropica and L. infantum/L. tropica groups of species DNAs, respectively. We optimized the experimental conditions of a duplex ultra-fast PCR. The amplification is performed using a portable Palm convection PCR machine within 18 min, and the products are detected using an LF cassette within 10 min. The test allows the identification of the infecting species according to the position and number of test lines revealed. Tested on a selection of DNAs of representative Leishmania strains of the three studied species (N = 37), the ultra-fast duplex PCR-LF showed consistent, stable and reproducible results. The analytical limit of detection of the test was 0.4 pg for L. major, 4 pg for L. infantum and 40 pg for L. tropica.

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

The continuous genetic evolution of SARS-CoV-2 resulting in the immune escape variant of concern (VoC) Omicron poses a challenge to rapid and accurate diagnosis of infection, especially in high-risk groups such as healthcare workers. We performed a clinical study to determine the diagnostic accuracy and robustness of a second-generation rapid antigen test compared to a first-generation rapid antigen test with an RT-qPCR-based assay as gold standard, for early detection of infections with SARS-CoV-2 Omicron VoC. A total of 428 healthcare workers with COVID-19-associated symptoms or during routine testing participated in the study and completed a questionnaire on infection-associated symptoms, previous SARS-CoV-2 infections, and vaccination status. All participants performed a second- and first-generation rapid antigen test on the day of presentation and repeated the test 2 days later, and a diagnostic SARS-CoV-2 RT-qPCR assay was performed. qPCR-confirmed SARS-CoV-2 infections (n = 104) with Omicron VoC (BA.2, BA.4, BA.5) were detected by the first-generation rapid antigen test with a sensitivity of 83.7% (95% CI 75.12%-90.18%), whereas the second-generation rapid antigen test performed with a sensitivity of 89.4% (95% CI 81.9%-94.6%). Increased sensitivity of the second-generation rapid antigen test led to earlier detection of SARS-CoV-2 infection, while lower test sensitivity of the first-generation rapid antigen test was compensated by repeated testing 2 days later. Moreover, direct in vitro comparison revealed a lower limit of detection for the second-generation rapid antigen test for isolates of currently circulating Omicron sub-lineages BA.5.2, BQ.1, and XBB.1. 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.

583P A rapid blood test for the earlier detection of colorectal cancer

583P A rapid blood test for the earlier detection of colorectal cancer

Development and evaluation of PlasmoPod: A cartridge-based nucleic acid amplification test for rapid malaria diagnosis and surveillance.

Malaria surveillance is hampered by the widespread use of diagnostic tests with low sensitivity. Adequate molecular malaria diagnostics are often only available in centralized laboratories. PlasmoPod is a novel cartridge-based nucleic acid amplification test for rapid, sensitive, and quantitative detection of malaria parasites. PlasmoPod is based on reverse-transcription quantitative polymerase chain reaction (RT-qPCR) of the highly abundant Plasmodium spp. 18S ribosomal RNA/DNA biomarker and is run on a portable qPCR instrument which allows diagnosis in less than 30 minutes. Our analytical performance evaluation indicates that a limit-of-detection as low as 0.02 parasites/μL can be achieved and no cross-reactivity with other pathogens common in malaria endemic regions was observed. In a cohort of 102 asymptomatic individuals from Bioko Island with low malaria parasite densities, PlasmoPod accurately detected 83 cases, resulting in an overall detection rate of 81.4%. Notably, there was a strong correlation between the Cq values obtained from the reference RT-qPCR assay and those obtained from PlasmoPod. In an independent cohort, using dried blood spots from malaria symptomatic children living in the Central African Republic, we demonstrated that PlasmoPod outperforms malaria rapid diagnostic tests based on the PfHRP2 and panLDH antigens as well as thick blood smear microscopy. Our data suggest that this 30-minute sample-to-result RT-qPCR procedure is likely to achieve a diagnostic performance comparable to a standard laboratory-based RT-qPCR setup. We believe that the PlasmoPod rapid NAAT could enable widespread accessibility of high-quality and cost-effective molecular malaria surveillance data through decentralization of testing and surveillance activities, especially in elimination settings.

Rapid Detection of blaKPC in Carbapenem-Resistant Enterobacterales Based on CRISPR/Cas13a

Klebsiella pneumoniae carbapenemase (KPC) is a crucial enzyme that causes carbapenem resistance in Enterobacterales, and infections by these "superbugs" are extremely challenging to treat. Therefore, there is a pressing need for a rapid and accurate KPC detection test to control the prevalence of carbapenem-resistant Enterobacterales (CREs). In this study, we established a novel method for detection of blaKPC, the gene responsible for encoding KPC, based on a recombinase polymerase amplification (RPA) and a CRISPR/Cas13a reaction coupled to fluorophore activation (termed RPA-Cas13a assay). We carefully selected a pair of optimal amplification primers for blaKPC and achieved a lower limit of detection of approximately 2.5 copies/μL by repeatedly amplifying a recombinant plasmid containing blaKPC. The RPA-Cas13a assay demonstrated a sensitivity of 96.5% and specificity of 100% when tested on 57 blaKPC-positive CRE strains, which were confirmed by DNA sequencing. Moreover, in 311 sputum samples, the theoretical antibiotic resistance characteristics of blaKPC-positive strains obtained by the RPA-Cas13a assay were highly consistent with the results of antibiotic susceptibility test (Kappa = 0.978 > 0.81, P < 0.01). In conclusion, the RPA-Cas13a system is a simple and one-hour efficient technology for the detection of a potentially fatal antibiotic resistance gene.

Screening for canine coronavirus, canine influenza virus, and severe acute respiratory syndrome coronavirus 2 in dogs during the coronavirus disease-2019 pandemic.

Although most cases of coronavirus disease-2019 (COVID-19) are in humans, there is scientific evidence to suggest that the virus can also infect dogs and cats. This study investigated the circulation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), canine coronavirus (CCV), and canine influenza virus (CIV) in domiciled and/or stray dogs from different locations in the State of Minas Gerais, Brazil, during the COVID-19 pandemic. In total, 86 dogs living in homes, on the streets, or in shelters in the cities of Taiobeiras, Salinas, Araçuaí, and Almenara were randomly selected for this study. The COVID Ag Detect® Self-Test was used to detect SARS-CoV-2. The ACCUVET CCV AG TEST - CANINE CORONAVIROSIS® was used to detect CCV, whereas canine influenza was detected using the ACCUVET CIV AG TEST - INFLUENZA CANINA®. All collected data were mapped using QGIS 3.28.1 for spatial data analysis and the identification of disease distribution patterns. Descriptive analysis of the collected data, prevalence calculations, odds ratios (ORs), and 95% confidence intervals, when possible, was performed. Of the 86 animals tested, only one dog tested positive for SARS-CoV-2 using the rapid test for viral antigen detection. No animals tested positive for CIV. Canine coronavirus was detected in almost half of the animals tested in Almenara. Severe acute respiratory syndrome-CoV-2 had a low prevalence (1.16%), versus 15.62% for CCV. Although the results were not significant, the age and breed of animals appeared to be associated with the occurrence of CCV. The results indicated that younger animals were 2.375-fold more likely to be infected. Likewise, purebred animals were more likely to contract the disease (OR = 1.944). The results indicate the need to maintain preventive measures against CCV, canine influenza, and SARS-CoV-2 in dogs. More studies are needed to better elucidate the panorama of these diseases in dogs, mainly in underdeveloped and developing countries.

Sample size determination for point-of-care COVID-19 diagnostic tests: a Bayesian approach

BackgroundIn a pandemic setting, it is critical to evaluate and deploy accurate diagnostic tests rapidly. This relies heavily on the sample size chosen to assess the test accuracy (e.g. sensitivity and specificity) during the diagnostic accuracy study. Too small a sample size will lead to imprecise estimates of the accuracy measures, whereas too large a sample size may delay the development process unnecessarily. This study considers use of a Bayesian method to guide sample size determination for diagnostic accuracy studies, with application to COVID-19 rapid viral detection tests. Specifically, we investigate whether utilising existing information (e.g. from preceding laboratory studies) within a Bayesian framework can reduce the required sample size, whilst maintaining test accuracy to the desired precision.MethodsThe method presented is based on the Bayesian concept of assurance which, in this context, represents the unconditional probability that a diagnostic accuracy study yields sensitivity and/or specificity intervals with the desired precision. We conduct a simulation study to evaluate the performance of this approach in a variety of COVID-19 settings, and compare it to commonly used power-based methods. An accompanying interactive web application is available, which can be used by researchers to perform the sample size calculations.ResultsResults show that the Bayesian assurance method can reduce the required sample size for COVID-19 diagnostic accuracy studies, compared to standard methods, by making better use of laboratory data, without loss of performance. Increasing the size of the laboratory study can further reduce the required sample size in the diagnostic accuracy study.ConclusionsThe method considered in this paper is an important advancement for increasing the efficiency of the evidence development pathway. It has highlighted that the trade-off between lab study sample size and diagnostic accuracy study sample size should be carefully considered, since establishing an adequate lab sample size can bring longer-term gains. Although emphasis is on its use in the COVID-19 pandemic setting, where we envisage it will have the most impact, it can be usefully applied in other clinical areas.

Rapid culture-based LNZ test for detection of linezolid susceptibility/resistance in staphylococci and enterococci

A rapid, easy-to-handle, cost-effective and universal culture-based test was developed for the identification of linezolid resistance among the most clinically relevant enterococcal and staphylococcal species. Our technique was tested using linezolid-resistant (n = 50) and linezolid-susceptible (n = 67) Gram-positive isolates: 34 Enterococcus faecium, 20 Enterococcus faecalis, 20 Staphylococcus aureus, 38 Staphylococcus epidermidis, and 5 Staphylococcus capitis. The susceptibility/resistance phenotype of E. faecium, E. faecalis, S. aureus, and S. epidermidis to linezolid was detected within 4.5 hours, while an extended timeframe was actually required for S. capitis (6.5 hours). The Rapid LNZ test showed a full agreement with the standard broth microdilution method, independently of the molecular resistance mechanism and MIC values, with sensitivities and specificities of 100% for all species.

Development of a loop-mediated isothermal amplification (LAMP)-based electrochemical test for rapid detection of SARS-CoV-2

Rapid, reliable, sensitive, portable, and accurate diagnostics are required to control disease outbreaks such as COVID-19 that pose an immense burden on human health and the global economy. Here we developed a loop-mediated isothermal amplification (LAMP)-based electrochemical test for the detection of SARS-CoV-2 that causes COVID-19. The test is based on the oxidation-reduction reaction between pyrophosphates (generated from positive LAMP reaction) and molybdate that is detected by cyclic voltammetry using inexpensive and disposable carbon screen printed electrodes. Our test showed higher sensitivity (detecting as low as 5.29 RNA copies/μL) compared to the conventional fluorescent reverse transcriptase (RT)-LAMP. We validated our tests using human serum and saliva spiked with SARS-CoV-2 RNA and clinical (saliva and nasal-pharyngeal) swab samples demonstrating 100% specificity and 93.33% sensitivity. Our assay provides a rapid, specific, and sensitive test with an electrochemical readout in less than 45min that could be adapted for point-of-care settings.

THE INCIDENCE OF ADENOVIRUS AND ROTAVIRUS IN PEDIATRIC PATIENTS WITH GASTROENTERITIS

Symptomatic or asymptomatic pediatric diarrhea is a worldwide public health problem, one of the important causes of morbidity and mortality in children 5 years and below. The main causes of viral acute gastroenteritis in the childhood are adenoviruses, rotaviruses, astroviruses and caliciviruses, especially between six months and two years of age. The aim of this paper was to establish the incidence of gastroenteritis with adenovirus and rotavirus in pediatric patients in Curtea de Arges (Arges) in 17 months (between January 1st, 2021 and June 1st, 2022). The immunochromatographic assay was used with OnSite Rota/Adeno Ag Rapid Test for viral antigens simultaneous detection in stool samples. There were differences between number of infections with rotavirus or adenovirus, depend of children age and patients gender (the rotavirus infections were more frequent than those determined by adenoviruses, in male patients, between six and 18 months age), and the co-infections were occurred, too (10.75% from all cases).

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).

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. 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. 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. 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. ISRCTN142269.

Development of a Colorimetric Urease Test Based on Au NPS Capped with Anthocyanin for the Rapid Detection of Helicobacter pylori through Multiple Readouts

AbstractIn this work, we have reported use of anthocyanin capped gold nanoparticles (Ant@Au NPs)‐incorporated colorimetric urease test for rapid, sensitive and economic detection of Helicobacter pylori (H. pylori). This test containing Ant@Au NPs, urea, sodium phosphate buffer (PBS) and sodium azide (NaN3) was prepared at pH 5 with red solution owing to dispersity of Ant@Au NPs, urease enzyme secreted from H. pylori cause production of ammonia (NH3) via hydrolysis of urea, then which makes reaction environment alkaline (pH 8.2). The limit of detection for this Ant@Au NPs based urease test was determined to be to 102 CFU/mL with proportional to increasing incubation time. However, distinct color change was observed with 104 CFU/mL H. pylori suspensions in 15 min. The anthocyanin molecules existing on surface of Ant@Au NPs were easily deprotonated from hydroxyl groups in the alkaline condition, which caused various changes on Ant@Au NPs including quite much negative charges on the surface of Ant@Au NPs analyzed by Zeta potential, aggregation of Ant@Au NPs demonstrated by STEM, DLS and spectrophotometer, and turning the color of test solution to purple evaluated by a naked eye and digital process imaging system.

Reverse transcription loop‑mediated isothermal amplification has a high performance in the detection of SARS‑CoV‑2 in saliva samples and nasal swabs from asymptomatic and symptomatic individuals.

The detection of coronavirus disease 2019 cases represents a significant challenge at the epidemiological level. Limitations exist in effectively detecting asymptomatic cases, achieving good follow-up in hospitals without the infrastructure for reverse transcription-quantitative PCR (RT-qPCR) or in difficult-to-access areas and developing methods with the need for less invasive sampling procedures. Therefore, the present study evaluated the performance of the direct reverse transcription loop-mediated isothermal amplification (RT-LAMP) test for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the saliva and nasal samples of asymptomatic individuals belonging to the university population. In addition, this test was also assessed for effectiveness in symptomatic individuals referred from a hospital with poor infrastructure in molecular biology and located outside the urban area. The RT-LAMP assay was compared with the results obtained from the RT-qPCR nasopharyngeal swab test, where the diagnosis was confirmed by lateral flow immunoassay test for rapid antigen detection. A total of 128 samples were analyzed, of which 43% were symptomatic positive individuals, 25% were asymptomatic positive individuals and 32% were SARS-CoV2-negative control individuals. Among positive individuals, no differences were found between the Cq values determined by RT-qPCR. A sensitivity of 96.5% and a specificity of 97.6% was reported for the detection of SARS-CoV-2 in symptomatic individuals by salivary and nasal RT-LAMP, as well as a sensitivity of 100% and a specificity of 97.6% for the detection of SARS-CoV-2 in asymptomatic individuals. These findings indicated that performance of the direct RT-LAMP test using saliva and nasal samples has high sensitivity and specificity, which in turn suggest that it is a viable and reliable alternative for use in epidemiological monitoring.

Diagnostic Accuracy of Rapid Antibody Detection Test for Scrub Typhus

Diagnostic Accuracy of Rapid Antibody Detection Test for Scrub Typhus

Focus Issue Articles on Diagnostic Assay Development and Validation: The Science of Getting It Right

Focus Issue Articles on Diagnostic Assay Development and Validation: The Science of Getting It Right

Evaluation of the AmplifyRP XRT+ Kit for the Detection of Xylella fastidiosa by Recombinase Polymerase Amplification

Xylella fastidiosa is a quarantine priority pest in Europe and several other countries as it represents a major threat to many cultivated and wild plants. Early detection of the pathogen is needed to reduce potential losses and to stop the bacterial dissemination. Very few molecular methods are available for rapid field detection to identify the pathogen. Here, we evaluated a new rapid commercial detection test called AmplifyRP, based on molecular recombinase polymerase amplification (RPA). The AmplifyRP test was compared with the quantitative PCR (qPCR) Harper's assay, which represents the standard method used in most laboratories all over the world. Specificity was tested in vitro on a panel of target and nontarget strains. Additionally, the sensitivity of the RPA test was tested on X. fastidiosa genomic DNA, and the selectivity was compared between different host plant matrices spiked with X. fastidiosa cell suspensions. Although the qPCR assay showed a higher sensitivity than the RPA test, the latter appeared to be a very specific, rapid, and portable technique for which no skills are required to proceed. These findings should enable growers and inspectors to choose an appropriate diagnostic method. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Development of a Raman-Based Test for Rapid Thiol Scavenger Detection in Oil and Gas Applications

A rapid and efficient Raman-based method to identify potential thiol scavengers for oil and gas applications is described. The procedure was validated using the nucleophilic addition of ethanethiol (EtSH) to several commercial hydrogen sulfide (H2S) scavengers under sonication conditions at room temperature. A success metric was defined by the appearance of a strong C–S–C band in the Raman spectrum of the reaction mixture associated with the formation of a new thioether functionality. The simplicity of the method facilitates the sampling of a wide variety of substrates as well as the introduction of multiple variations to the original test protocol, such as the use of different solvents, sources of energy, the addition of catalysts, and temperature changes.

Comparison of diagnostic performance of RT-qPCR, RT-LAMP and IgM/IgG rapid tests for detection of SARS-CoV-2 among healthcare workers in Brazil

BackgroundCOVID-19 has become a major public health problem after the outbreak caused by SARS-CoV-2 virus. Great efforts to contain COVID-19 transmission have been applied worldwide. In this context, accurate and fast diagnosis is essential. MethodsIn this prospective study, we evaluated the clinical performance of three different RNA-based molecular tests – RT-qPCR (Charité protocol), RT-qPCR (CDC (USA) protocol) and RT-LAMP – and one rapid test for detecting anti-SARS-CoV-2 IgM and IgG antibodies. ResultsOur results demonstrate that RT-qPCR using the CDC (USA) protocol is the most accurate diagnostic test among those evaluated, while oro-nasopharyngeal swabs are the most appropriate biological sample. RT-LAMP was the RNA-based molecular test with lowest sensitivity while the serological test presented the lowest sensitivity among all evaluated tests, indicating that the latter test is not a good predictor of disease in the first days after symptoms onset. Additionally, we observed higher viral load in individuals who reported more than 3 symptoms at the baseline. Nevertheless, viral load had not impacted the probability of testing positive for SARS-CoV-2. ConclusionOur data indicates that RT-qPCR using the CDC (USA) protocol in oro-nasopharyngeal swabs samples should be the method of choice to diagnosis COVID-19.