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Human monkeypox (mpox) has recently become a global public health emergency; however, assays that detect mpox infection are not widely available, largely due to cross-reactivity within the Orthopoxvirus genus. Immunoassay development was largely confined to researchers who focus on biothreats and endemic areas (Central and West Africa) until the 2022 outbreak. As was noted in the COVID-19 pandemic, antigen detection assays, integrated with molecular assays, are necessary to help curb the spread of disease. Antigen-detecting immunoassays offer the advantage of providing results ranging from within min to h and in lateral flow formats; they can be deployed for point-of-care, home, or field use. This study reports the development of an mpox-specific antigen detection immunoassay developed on a multiplexed, magnetic-bead-based platformutilizing reagents fromall research sectors (commercial, academic, and governmental). Two semi-quantitative assays were developed in parallel and standardized with infectious mpox virus (MPXV) cell culture fluid and MPXV-positive non-human primate (NHP) sera samples. These assays could detect viral antigens in serum, were highly specific toward MPXV as compared to other infectious orthopoxviruses (vaccinia virus, cowpox virus, and camelpox virus), and exhibited a correlation with quantitative PCR results from an NHP study. Access to a toolbox of assays for mpox detection will be key for identifying cases and ensuring proper treatment, as MPXV is currently a global traveler. [ABSTRACT FROM AUTHOR]

Human monkeypox (mpox) has recently become a global public health emergency; however, assays that detect mpox infection are not widely available, largely due to cross-reactivity within the Orthopoxvirus genus. Immunoassay development was largely confined to researchers who focus on biothreats and endemic areas (Central and West Africa) until the 2022 outbreak. As was noted in the COVID-19 pandemic, antigen detection assays, integrated with molecular assays, are necessary to help curb the spread of disease. Antigen-detecting immunoassays offer the advantage of providing results ranging from within min to h and in lateral flow formats; they can be deployed for point-of-care, home, or field use. This study reports the development of an mpox-specific antigen detection immunoassay developed on a multiplexed, magnetic-bead-based platform utilizing reagents from all research sectors (commercial, academic, and governmental). Two semi-quantitative assays were developed in parallel and standardized with infectious mpox virus (MPXV) cell culture fluid and MPXV-positive non-human primate (NHP) sera samples. These assays could detect viral antigens in serum, were highly specific toward MPXV as compared to other infectious orthopoxviruses (vaccinia virus, cowpox virus, and camelpox virus), and exhibited a correlation with quantitative PCR results from an NHP study. Access to a toolbox of assays for mpox detection will be key for identifying cases and ensuring proper treatment, as MPXV is currently a global traveler.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused considerable disruption worldwide. For efficient SARS-CoV-2 detection, new methods of rapid, non-invasive sampling are needed. This study aimed to investigate the stability of SARS-CoV-2 in a novel medium for gargle-lavage (GL) self-sampling and to compare the performance of SARS-CoV-2 detection in paired self-collected GL and clinician-obtained nasopharyngeal swab (NPS) samples. The stability study for SARS-CoV-2 preservation in a novel medium was performed over 14 days (4 °C, 24–27 °C, and 37 °C). In total, 494 paired GL and NPS samples were obtained at the University Hospital in Olomouc in April 2021. SARS-CoV-2 detection in paired samples was performed with a SARS-CoV-2 Nucleic Acid Detection Kit (Zybio, Chongqing Municipality, Chongqing, China), an Elecsys® SARS-CoV-2 Antigen assay (Roche Diagnostics, Mannheim, Germany), and a SARS-CoV-2 Antigen ELISA (EUROIMMUN, Lübeck, Germany). The stability study demonstrated excellent SARS-CoV-2 preservation in the novel medium for 14 days. SARS-CoV-2 was detected in 55.7% of NPS samples and 55.7% of GL samples using rRT-PCR, with an overall agreement of 91.9%. The positive percent agreement (PPA) of the rRT-PCR in the GL samples was 92.7%, and the negative percent agreement (NPA) was 90.9%, compared with the NPS samples. The PPA of the rRT-PCR in the NPS and GL samples was 93.2% when all positive tests were used as the reference standard. Both antigen detection assays showed poor sensitivity compared to rRT-PCR (33.2% and 36.0%). rRT-PCR SARS-CoV-2 detection in self-collected GL samples had a similar PPA and NPA to that of NPSs. GL self-sampling offers a suitable and more comfortable alternative for SARS-CoV-2 detection. [ABSTRACT FROM AUTHOR]

Diagnostic methods based on SARS-CoV-2 antigen detection are a promising alternative to SARS-CoV-2 RNA amplification. We evaluated the automated chemiluminescence-based Lumipulse® G SARS-CoV-2 Ag assay as compared to real time assays (combined results from RT-PCR Allplex™ SARS-CoV-2 assay and Easy SARS-CoV-2 WE kit) on 513 nasopharyngeal swabs (NPS). Among these, 53.6% resulted positive to RT-PCR, considered as the reference test. Compared to the reference test, overall sensitivity and specificity of Lumipulse® G SARS-CoV-2 Ag assay were 84.0%, and 89.1%, respectively, and overall agreement between the antigen and molecular assays was substantial (κ = 0.727). When stratifying samples into groups based on ranges of RT-PCR cycle threshold (Ct), the antigen test sensitivity was >95% for samples with Ct

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused considerable disruption worldwide. For efficient SARS-CoV-2 detection, new methods of rapid, non-invasive sampling are needed. This study aimed to investigate the stability of SARS-CoV-2 in a novel medium for gargle-lavage (GL) self-sampling and to compare the performance of SARS-CoV-2 detection in paired self-collected GL and clinician-obtained nasopharyngeal swab (NPS) samples. The stability study for SARS-CoV-2 preservation in a novel medium was performed over 14 days (4 °C, 24–27 °C, and 37 °C). In total, 494 paired GL and NPS samples were obtained at the University Hospital in Olomouc in April 2021. SARS-CoV-2 detection in paired samples was performed with a SARS-CoV-2 Nucleic Acid Detection Kit (Zybio, Chongqing Municipality, Chongqing, China), an Elecsys® SARS-CoV-2 Antigen assay (Roche Diagnostics, Mannheim, Germany), and a SARS-CoV-2 Antigen ELISA (EUROIMMUN, Lübeck, Germany). The stability study demonstrated excellent SARS-CoV-2 preservation in the novel medium for 14 days. SARS-CoV-2 was detected in 55.7% of NPS samples and 55.7% of GL samples using rRT-PCR, with an overall agreement of 91.9%. The positive percent agreement (PPA) of the rRT-PCR in the GL samples was 92.7%, and the negative percent agreement (NPA) was 90.9%, compared with the NPS samples. The PPA of the rRT-PCR in the NPS and GL samples was 93.2% when all positive tests were used as the reference standard. Both antigen detection assays showed poor sensitivity compared to rRT-PCR (33.2% and 36.0%). rRT-PCR SARS-CoV-2 detection in self-collected GL samples had a similar PPA and NPA to that of NPSs. GL self-sampling offers a suitable and more comfortable alternative for SARS-CoV-2 detection.

Abstract Background We examined the performance of four in-clinic Giardia diagnostic tests by comparing results to three laboratory methods for detection of Giardia. A set of 177 fecal samples originally submitted to a commercial laboratory by veterinarians for routine ova and parasite (O&P) testing was used. Specimens were examined by direct immunofluorescence assay (DFA) for presence of Giardia cysts which served as the gold standard. Fecal samples were tested using a Giardia-specific cyst wall antigen microtiter plate format enzyme-linked immunosorbent assay (ELISA) and each of the in-clinic assays adhering to the package insert for each kit. Results Evaluated were four in-clinic antigen test kits: VetScan® Canine Giardia Rapid Test (Abaxis), Anigen® Rapid CPV-CCV-Giardia Antigen Test (BioNote), SNAP® Giardia Test (IDEXX) and Witness® Giardia Test (Zoetis). In the comparison of the in-clinic tests to the DFA standard test sensitivity ranged between 70.0–87.1%, and specificity ranged between 71.1–93.4%. Conclusion Of the tests evaluated here, the SNAP test had the highest sensitivity and specificity. The SNAP test had the highest percent positive and percent negative agreement when compared to the microtiter plate format ELISA and the O&P assay.

• Correlation between the Lumipulse Ag concentrations and Ct values of RT-PCR assays • Chemiluminescence-based antigen test reliable to identify high viral loads • Satisfactory performance of the Lumipulse G® SARS-CoV-2 Ag assay Diagnostic methods based on SARS-CoV-2 antigen detection are a promising alternative to SARS-CoV-2 RNA amplification. We evaluated the automated chemiluminescence-based Lumipulse® G SARS-CoV-2 Ag assay as compared to real time assays (combined results from RT-PCR Allplex™ SARS-CoV-2 assay and Easy SARS-CoV-2 WE kit) on 513 nasopharyngeal swabs (NPS). Among these, 53.6% resulted positive to RT-PCR, considered as the reference test. Compared to the reference test, overall sensitivity and specificity of Lumipulse® G SARS-CoV-2 Ag assay were 84.0%, and 89.1%, respectively, and overall agreement between the antigen and molecular assays was substantial (κ = 0.727). When stratifying samples into groups based on ranges of RT-PCR cycle threshold (Ct), the antigen test sensitivity was >95% for samples with Ct <30. Linear regression analysis showed strong and highly significant correlation between the Lumipulse Ag concentrations and the RT-PCR Ct values (RdRp gene), irrespective of whether the Ct values from molecular test were combined in a unique regression analysis or analysed separately. Overall, chemiluminescence-based antigen assay may be reliably applied to NPS samples to identify individuals with high viral loads, more likely to transmit the virus. [ABSTRACT FROM AUTHOR]

Sequential infections of humans by the four different dengue serotypes (DENV-1–4) lead to neutralizing antibodies with group, cross, and type specificity. Virus neutralization of serotypes showed monotypic but mostly multitypic neutralization profiles due to multiple virus exposures. We have studied neutralization to heterologous, reference DENV serotypes using paired sera collected between days 6 and 37 after onset of fever. The DENV-primed neutralization profile of the first serum sample, which was monitored by a foci reduction neutralization test (FRNT), was boosted but the neutralization profile stayed unchanged in the second serum sample. In 45 of 47 paired serum samples, the predominant neutralization was directed against DENV serotypes distinct from the infecting serotype. Homologous neutralization studies using sera and viruses from the same area, 33 secondary sera from DENV-1 infected Cambodian patients and eight virus isolates from Cambodia, showed that the FRNT assay accurately predicted the lack of a predominant antibody response against the infecting DENV-1 serotype in contrast to FRNT results using the WHO set of DENV viruses. This report provides evidence that DENV-primed multitypic neutralizing antibody profiles were mainly boosted and stayed unchanged after secondary infection and that DENV neutralization was predominantly directed to heterologous DENV but not against the infecting homologous serotype.

Early identification and isolation of SARS-CoV-2-infected individuals is central to contain the COVID-19 pandemic. Nasopharyngeal swabs (NPS) serve as a specimen for detection by RT-PCR and rapid antigen screening tests. Saliva has been confirmed as a reliable alternative specimen for RT-PCR and has been shown to be valuable for diagnosing children and in repetitive mass testing due to its non-invasive collection. Combining the advantages of saliva with those of antigen tests would be highly attractive to further increase test capacities. Here, we evaluated the performance of the Elecsys SARS-CoV-2 Antigen assay (Roche) in RT-PCR-positive paired NPS and saliva samples (N = 87) and unpaired NPS (N = 100) with confirmed SARS-CoV-2 infection (Roche cobas SARS-CoV-2 IVD test). We observed a high positive percent agreement (PPA) of the antigen assay with RT-PCR in NPS, reaching 87.2% across the entire cohort, whereas the overall PPA for saliva was insufficient (40.2%). At Ct values ≤ 28, PPA were 100% and 91.2% for NPS and saliva, respectively. At lower viral loads, the sensitivity loss of the antigen assay in saliva was striking. At Ct values ≤ 35, the PPA for NPS remained satisfactory (91.5%), whereas the PPA for saliva dropped to 46.6%. In conclusion, saliva cannot be recommended as a reliable alternative to NPS for testing with the Elecsys Anti-SARS-CoV-2 Antigen assay. As saliva is successfully used broadly in combination with RT-PCR testing, it is critical to create awareness that suitability for RT-PCR cannot be translated to implementation in antigen assays without thorough evaluation of each individual test system.

Introduction: Chronic liver disease due to viral hepatitis continues to be a major global health concern. Timely diagnosis and treatment will prevent cirrhosis, risk of hepatocellular carcinoma (HCC), and requirement for liver transplantation. Numerous serum biomarkers are available for viral hepatitis that are helpful in diagnosis, measuring severity, progression of disease, evaluating the best therapeutic options, and monitoring antiviral treatment response. Determining the clinical use of available diagnostic tests can be challenging for the health care provider. Areas covered: This review article attempts to summarize the established and emerging serological markers for diagnosis and managing viral hepatitis. The literature search was performed in February 2018 and included MEDLINE and Embase databases for recent relevant literature on biomarkers for viral hepatitis. Expert Commentary: Despite the discovery of several candidate biomarkers, translating these to clinical practice in viral hepatitis and HCC remains challenging. While limited availability of the new biomarkers in prevalent geographic areas and significant cost remain major obstacles, there have been exciting developments in this field. Understanding the detection limits and sensitivity of these markers and translating them into clinical use is important in management of viral hepatitis and complications of liver disease such as cirrhosis and hepatocellular cancer. [ABSTRACT FROM AUTHOR]

Background. Streptococcus pneumoniae is considered the leading bacterial cause of pneumonia in adults. Yet, it was not commonly detected by traditional culture-based and conventional urinary testing in a recent multicenter etiology study of adults hospitalized with community-acquired pneumonia (CAP). We used novel serotype-specific urinary antigen detection (SSUAD) assays to determine whether pneumococcal cases were missed by traditional testing. Methods. We studied adult patients hospitalized with CAP at 5 hospitals in Chicago and Nashville (2010-2012) and enrolled in the Etiology of Pneumonia in the Community (EPIC) study. Traditional diagnostic testing included blood and sputum cultures and conventional urine antigen detection (ie, BinaxNOW). We applied SSUAD assays that target serotypes included in the 13-valent pneumococcal conjugate vaccine (PCV13) to stored residual urine specimens. Results. Among 1736 patients with SSUAD and ≥1 traditional pneumococcal test performed, we identified 169 (9.7%) cases of pneumococcal CAP. Traditional tests identified 93 (5.4%) and SSUAD identified 76 (4.4%) additional cases. Among 14 PCV13- serotype cases identified by culture, SSUAD correctly identified the same serotype in all of them. Cases identified by SSUAD vs traditional tests were similar in most demographic and clinical characteristics, although disease severity and procalcitonin concentration were highest among those with positive blood cultures. The proportion of PCV13 serotype cases identified was not significantly different between the first and second July-June study periods (6.4% vs 4.0%). Conclusions. Although restricted to the detection of only 13 serotypes, SSUAD testing substantially increased the detection of pneumococcal pneumonia among adults hospitalized with CAP. Keywords. pneumonia; etiology; Streptococcus pneumoniae; [ABSTRACT FROM AUTHOR]

There are four distinct antigenic serotypes of dengue viruses (DENV-1-4). Sequential infections with different serotypes lead to cross-reactive but also serotype-specific neutralizing antibody responses. Neutralization assays are considered as gold standard for serotype-specific antibody detection. However, for retrospective seroprevalence studies, access to large serum quantities is limited making neutralization assays well-nigh impossible. Therefore, a serological test, wasting only 10 µL serum, was developed using fusion proteins of maltose binding protein and E protein domain 3 (MBP-ED3) as antigens. Twelve MBP-ED3 antigens for DENV-1-4, three MBP-ED3 antigens for WNV, JEV, and TBEV, and MBP were dotted onto a single nitrocellulose strip. ED3 dot assay results were compared to virus neutralization and ED3 ELISA test results, showing a >90% accordance for DENV-1 and a 100% accordance for DENV-2, making the test specifically useful for DENV-1/-2 serotype-specific antibody detection. Since 2010, DENV-1 has replaced DENV-2 as the dominant serotype in Cambodia. In a retrospective cohort analysis, sera collected during the DENV-1/-2 endemic period showed a shift to DENV-2-specific antibody responses in 2012 paralleled by the decline of DENV-2 infections. Altogether, the ED3 dot assay is a serum-, time- and money-saving diagnostic tool for serotype-specific antibody detection, especially when serum samples are limited.

Before the molecular age, cell culture was the gold standard for confirmatory diagnosis of viral and atypical infectious diseases. Typical cell culture methodologies are costly, require days (or weeks) for results, and require significant technical expertise. As a result, cell culture is impractical for timely diagnostic testing in most of the health care environments. Traditional bacterial culture methods, also have disadvantages due to the need for incubation, subsequent identification of pathogens, and significant technical expertise. This article discusses the general considerations of antigen and molecular assays and the merits and factors to consider when implementing diagnostic assays for several common pathogens., (Copyright © 2023 Elsevier Inc. All rights reserved.)

The sensitivity and specificity of SARS-CoV-2 antigen tests have not been widely assessed in children. We evaluated children presenting to outpatient care with Quidel Sofia SARS-CoV-2 antigen test (Sofia-Ag-RDT) compared against Cepheid Xpert Xpress SARS-CoV-2/Flu/RSV reverse transcriptase-polymerase chain reaction test from November 2020 to April 2021. Sofia-Ag-RDT had the highest sensitivity in symptomatic (82%; 95% confidence interval, 68%-91%) children., (© The Author(s) 2022. Published by Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

A prevalence of up to 30% of invasive fungal infections (IFI) has been reported from autopsy studies in patients treated for haematological malignancies. Despite substantial advances in the last decade, IFI are still associated with a mortality of up to more than 70%, in particular for those patients suffering from invasive aspergillosis. Some progress has been made in diagnostics with the advent of new non-culture based tools and the improvement of imaging techniques. However, the response rates are about 40-60% in the first-line treatment of IFI. Salvage therapy will be necessary for those being intolerant or refractory towards the respective first-line antifungal. Following a long period of stagnation, there has been a considerable progress during the last five years in the treatment of refractory IFI. This review highlights the new treatment options for the salvage setting in the context of the state-of-the-art management of IFI in cancer patients. [ABSTRACT FROM AUTHOR]

Results of coagulation studies on 21 homozygote patients with factor XII (FXII) deficiency revealed that all of them had no cross-reacting material (CRM) in their plasma. The 58 heterozygotes had in every instance an antigen level comparable to that of clotting activity namely, approximately 50% of normal. An analysis of all pertinent literature also showed that the presence of CRM is very rare in FXII deficiency. CRM is present in approximately 5% of homozygote patients. More precisely, seven of 145 patients. Only in one case, the antigen level was normal (FXII Washington). This prevalence appears lower than that observed for another contact phase factor (prekallikrein). The significance of blood abnormal forms of FXII has not been completely clarified yet. Their study appears useful in the attempt of clarifyng the structure-function relation of factor XII. [ABSTRACT FROM AUTHOR]

Despite recent advances in the last decade, invasive fungal infections are still associated with a high morbidity and mortality. Invasive fungal infections constitute severe infectious complications in patients with hematological malignancies receiving myelosuppressive chemotherapy or sustained immunosuppression after allogeneic transplant regimens. Following a long period of stagnation, considerable progress has been made during the last 5 years in non-culture-based diagnostics and in the treatment of invasive fungal infections. This review highlights recent developments in the epidemiology, diagnosis, and treatment in the context of state-of-the-art management of invasive fungal infections in cancer patients. [ABSTRACT FROM AUTHOR]

Sequential infections of humans by the four different dengue serotypes (DENV-1–4) lead to neutralizing antibodies with group, cross, and type specificity. Virus neutralization of serotypes showed monotypic but mostly multitypic neutralization profiles due to multiple virus exposures. We have studied neutralization to heterologous, reference DENV serotypes using paired sera collected between days 6 and 37 after onset of fever. The DENV-primed neutralization profile of the first serum sample, which was monitored by a foci reduction neutralization test (FRNT), was boosted but the neutralization profile stayed unchanged in the second serum sample. In 45 of 47 paired serum samples, the predominant neutralization was directed against DENV serotypes distinct from the infecting serotype. Homologous neutralization studies using sera and viruses from the same area, 33 secondary sera from DENV-1 infected Cambodian patients and eight virus isolates from Cambodia, showed that the FRNT assay accurately predicted the lack of a predominant antibody response against the infecting DENV-1 serotype in contrast to FRNT results using the WHO set of DENV viruses. This report provides evidence that DENV-primed multitypic neutralizing antibody profiles were mainly boosted and stayed unchanged after secondary infection and that DENV neutralization was predominantly directed to heterologous DENV but not against the infecting homologous serotype. [ABSTRACT FROM AUTHOR]

• Direct detection of SARS-CoV-2 using RDT is a simple approach to diagnose COVID-19. • Performance of RDTs has been assessed in more than 600 individuals. • The rate of success of the 6 RDTs was high (from 99.1% to 100%). • The specificity of SARS-CoV-2 RDTs was generally high (≥98.5%). • The overall sensitivity of the 6 RDTs was variable. • Sensitivity correlated with the delay of sampling after the onset of symptoms and the viral load. Direct detection of SARS-CoV-2 viral proteins in nasopharyngeal swabs using lateral flow immunoassays is a simple, fast and cheap approach to diagnose the infection. The performance of 6 SARS-CoV-2 antigen rapid diagnostic tests has been assessed in 634 hospitalized patients or outpatients including 297 patients found to be positive for SARS-CoV-2 RNA by means of RT-PCR and 337 patients presumed to be SARS-CoV-2 RNA-negative. The specificity of SARS-CoV-2 RDTs was generally high (398.5%). One assay had a lower specificity of 93.2%. The overall sensitivity of the 6 RDTs was variable, from 32.3% to 61.7%. Sensitivity correlated with the delay of sampling after the onset of symptoms and the viral load estimated by the Ct value in RT-PCR. Four out of 6 RDTs tested achieved sensitivities 380% when clinical specimens were collected during the first 3 days following symptom onset or with a Ct value ≤25. The present study shows that SARS-CoV-2 antigen can be easily and reliably detected by RDTs. These tests are easy and rapid to perform. However, the specificity and sensitivity of COVID-19 antigen RDTs may widely vary across different tests and must therefore be carefully evaluated before releasing these assays for realworld applications. [ABSTRACT FROM AUTHOR]

Early identification and isolation of SARS-CoV-2-infected individuals is central to contain the COVID-19 pandemic. Nasopharyngeal swabs (NPS) serve as a specimen for detection by RT-PCR and rapid antigen screening tests. Saliva has been confirmed as a reliable alternative specimen for RT-PCR and has been shown to be valuable for diagnosing children and in repetitive mass testing due to its non-invasive collection. Combining the advantages of saliva with those of antigen tests would be highly attractive to further increase test capacities. Here, we evaluated the performance of the Elecsys SARS-CoV-2 Antigen assay (Roche) in RT-PCR-positive paired NPS and saliva samples (N = 87) and unpaired NPS (N = 100) with confirmed SARS-CoV-2 infection (Roche cobas SARS-CoV-2 IVD test). We observed a high positive percent agreement (PPA) of the antigen assay with RT-PCR in NPS, reaching 87.2% across the entire cohort, whereas the overall PPA for saliva was insufficient (40.2%). At Ct values ≤ 28, PPA were 100% and 91.2% for NPS and saliva, respectively. At lower viral loads, the sensitivity loss of the antigen assay in saliva was striking. At Ct values ≤ 35, the PPA for NPS remained satisfactory (91.5%), whereas the PPA for saliva dropped to 46.6%. In conclusion, saliva cannot be recommended as a reliable alternative to NPS for testing with the Elecsys Anti-SARS-CoV-2 Antigen assay. As saliva is successfully used broadly in combination with RT-PCR testing, it is critical to create awareness that suitability for RT-PCR cannot be translated to implementation in antigen assays without thorough evaluation of each individual test system. [ABSTRACT FROM AUTHOR]

Background Rapid antigen detection testing (RADT) is needed to differentiate Group A Streptococcal (GAS) pharyngitis from viral pharyngitis. Guidelines do not recommend RADT in patients with viral symptoms or in children <3 years old without GAS exposure. Reduction in unnecessary RADT use may impact inappropriate antibiotic use by decreasing prescriptions in children likely colonized with GAS. We examined the impact of guideline concordant education of appropriate RADT and antibiotic use in pharyngitis on providers' (physician and APRN) use of RADT in an academic and private pediatric primary care clinic. Methods Retrospective chart review of 1,085 healthy children, age 1–5 years old, seen in clinics between September 2015 and March 2019 (355 pre- and 730 post-education; 211 academic and 874 private). Education occurred in 3/2017. Cases selected had either complaint of sore throat, RADT, or diagnosis of GAS pharyngitis or pharyngitis. Data collected included the presence of viral symptoms (e.g. cough, rhinorrhea), RADT/GAS culture results, diagnosis, and prescribed antibiotics. RADT was deemed unnecessary for all children < 3 years old without GAS exposure, in patients with ≥ 2 viral symptoms, or in patients ≥ 3 years old without pharyngitis. Results Overall, RADT use decreased from pre to post intervention (72.1% vs. 23.4% of patients, P ≤ 0.0001). Unnecessary RADT use decreased overall (50.4% vs. 16.2%, P ≤ 0.0001), in all clinics (private: 56.2% vs. 16.0%, P ≤ 0.0001; academic: 38.1% vs. 17.4%, P = 0.0012), and with all providers (physician: 41.6% vs. 18.3%, P ≤ 0.0001; APRN: 58.8% vs. 14.1%, P ≤ 0.0001). Unnecessary RADT use decreased for children <3 years old (28.1% vs. 7.4%, P ≤ 0.0001) and ≥2 viral symptoms (65.7% vs. 16.5%, P ≤ 0.0001). Conclusion Unnecessary RADT use decreased in the post-education period overall (34%), in children <3 years old (21%), and in patients with ≥ 2 viral symptoms (49%). Reductions were also seen in both academic (21%) and private (40%) clinics as well as with both physicians (23%) and ARPNs (45%). Limitations include lack of a control group and sample size variance by the clinic. We observed positive trends in RADT reduction following provider education in private and academic settings; however, further research including control and optimal sample size is needed to confirm any direct impact. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background Guidelines support the use of toxin tests after C. difficile antigen detection or nucleic acid amplification tests (e.g. PCR) to help clinicians distinguish colonization from infection and reduce overdiagnosis but the safety of toxin-based diagnostic approaches remains controversial. Methods Five California hospitals monitored hospitalized adults with C. difficile testing before and after operational changes to reduce test-related overdiagnosis (2016–2018). Four added a toxin test to an existing GDH antigen/PCR-based approach and/or changed reporting to encourage the use of toxin results for clinical decision-making (i.e."toxin-dominant reporting"). One used the same test (toxin only) and reporting strategy throughout. All used a standardized tool to document clinical outcomes and treatment four days after testing (i.e. Day 5). Results In total, 1,034 patients had a Day 5 assessment with PCR-dominant reporting (pre-operational changes); 2,511 patients had a Day 5 assessment with toxin-dominant reporting (post-operational changes and single facility with no test change). Fewer Toxin-negative/PCR-positive (Toxin−/PCR+) patients received treatment with toxin-dominant reporting (median change: −52.1% [interquartile range (IQR): −35.1%, −69.1%]; aggregate P < 0.001). Day 5 outcomes were similar or better with toxin-dominant reporting despite less treatment. Patient discharge rates and in hospital diarrheal recovery was greater in the subset of Toxin−/PCR+ patients during the toxin-dominant reporting period: median discharge rate change = 8.8% [IQR: 1.5%, 11.9%] (aggregate P = 0.04); median diarrheal recovery rate change = 11.8% [IQR: 8.8%, 18.2%] (aggregate P = 0.018). Conclusion In a 5-center study, toxin-dominant test result reporting decreased anti- C. difficile treatment and improved discharge rates and diarrheal recovery in Toxin−/PCR+ patients. More work is needed to determine the rate of C. difficile -related adverse events in Toxin−/PCR+ patients. Disclosures All Authors: No reported Disclosures. [ABSTRACT FROM AUTHOR]

The SARS-CoV-2 pandemic is ongoing worldwide, causing prolonged pressure on molecular diagnostics. Viral antigen (Ag) assays have several advantages, ranging from lower cost to shorter turnaround time to detection. Given the rare occurrence of low-load viremia, antigen assays for SARSCoV-2 have focused on nasopharyngeal swab and saliva as biological matrices, but their effectiveness must be validated. We assayed here the performances of the novel quantitative Liaison® SARSCoV-2 Ag assay on 119 nasopharyngeal swabs and obtained results were compared with Hologic Panther and Abbott m2000 RT-qPCR. The Ag assay demonstrated a good correlation with viral load, shorter turnaround time, and favorable economics. The best performance was obtained in the acute phase of disease.

Inherited protein C (PC) deficiency increases risk of venous thromboembolism (VTE) by 5 to 10-fold in thrombosis-prone families; however, heterozygous PC deficiency alone does not determine that a subject has thrombophilia. Protein C deficient subjects, who lack additional inherited risk factors such as factor V Leiden or have no major acquired risk factors, may not suffer from VTE. In addition, PC deficiency may be acquired, often due to vitamin K antagonist treatment or liver disease. In contrast, homozygous or compound heterozygous PC deficiencies are rare and serious disorders, and affected infants are often in families with no history of PC deficiency or thrombosis. Laboratories commonly use the chromogenic PC assay to diagnose deficiency. Chromogenic assay is recommended due to its good specificity, but this assay fails to detect the rare type 2b deficiency where the defect is due to poor interaction with calcium ions, phospholipid, protein S, and factor Va and factor VIIIa. The clotting-based assay of PC is capable of detecting type 2b deficiency but it has reduced specificity. Importantly, PC level varies with age, adult reference ranges cannot be applied to babies or children and levels may not reach those of adults even in adolescence. Pre-analytical variables in the specimen affect measurement of PC, and can be assay-dependent; for example, a partially clotted sample will have falsely raised PC level by chromogenic assay but reduced level by clotting-based assay. Direct oral anticoagulants falsely raise PC level in the clotting-based assay but the standard chromogenic assay is unaffected., (© 2020 International Society on Thrombosis and Haemostasis.)

Hereditary deficiency of antithrombin, a natural anticoagulant, causes a thrombophilia with a high risk for venous thromboembolism. Guidance for laboratory testing to diagnose antithrombin deficiency include the use of an activity assay for initial testing, performing an antigen test and activity-to-antigen ratio when the activity level is low, using pediatric reference ranges until the age of 6 months, excluding acquired causes of low antithrombin (e.g. liver dysfunction, proteinuria, heparin, disseminated intravascular coagulation, thrombosis, surgery) or falsely normal/elevated results (e.g. argatroban, bivalirudin, dabigatran in factor IIa-based assays; rivaroxaban, apixaban, edoxaban, but not betrixaban in Xa-based assays). Molecular testing, if available, may help determine the risk for thrombosis as this might vary among the different mutations. Moreover, it will identify mutations that can be missed by traditional activity assays. Strategies for interpreting laboratory test results are provided., (© 2019 International Society on Thrombosis and Haemostasis.)

Background Group A Streptococcus (GAS), is currently diagnosed by throat culture or rapid antigen detection test (RADT) by a healthcare provider (HP), usually in an outpatient (OP) setting. There is current interest in expanding OTC diagnostics (FDA approved for HIV and hepatitis C) to other infectious diseases such as GAS pharyngitis. There are no data on parental acceptance of such a test. Our aim was to determine parental acceptance of expanding OTC diagnostic availability for GAS pharyngitis testing. Methods Caregivers of 3–18 years old in OP primary care pediatric clinics were given a questionnaire: data included demographics (excluding all patient identifiers), interest in buying/using an OTC GAS test, education level, type of health insurance (HI), comfort level swabbing their child, interest in available support/free hotline with the test. Statistical analysis included Mann–Whitney U test for non-continuous and T-test for continuous variables. Results 90 questionnaires were collected, 14 duplicates excluded. 34 (45%) parents indicated they would buy an OTC GAS test, 35 (46%) would not, 4 (5%) were unsure, 3 (4%) did not respond. There was no correlation between interest in OTC test and age (P = NS), or education level (P = NS). There was a trend of OTC test interest among those with private HI vs. Medicaid (P = 0.067). There was a statistically significant association between interest in buying an OTC GAS test and the following variables: high self-swab comfort level and availability of support (P = 0.009 and 0.001, respectively). The majority of participants [73/76 (96%)] did not respond to questions about acceptable pricing. Conclusion There was mixed interest in OTC GAS testing among respondents. Neither age nor educational level affected interest. Surprisingly, 96% of respondents declined to select a price they would pay for an OTC GAS test. Greater interest in OTC GAS testing among respondents with private HI suggests those parents are more likely to purchase the kits to avoid an HP visit (and co-payment). Since most respondents were comfortable self-swabbing or unsure, further education including swab tutorial and support availability may lead to greater comfort level with such testing. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background Antibody detection is the main method for diagnosis of coccidioidomycosis but has limitations including sensitivity and turnaround time. The MVISTA Coccidioides antigen enzyme immunoassay (EIA) is recommended for testing CSF in suspected Coccidioides meningitis. The early reports on urine and serum antigen testing evaluated small numbers of patients who were mostly immunocompromised with advanced disease. Methods A retrospective study, including all patients in whom Coccidioides antigen testing was performed between January 2013 and May 2017, was conducted at Maricopa Integrated Health System (MIHS). Sensitivity and specificity of antigen testing at MiraVista Diagnostics and antibody testing at MIHS or commercial laboratories were evaluated in 164 cases and 508 controls. Results The sensitivity of antigen testing was 51% and specificity was 99%. The sensitivity of antigen detection was highest if both urine and serum were tested (57%) than if only urine was tested (38%). The sensitivity of antibody testing was 84% and the specificity was 94% by immunodiffusion (ID). The sensitivity and specificity of antigen or ID antibody testing both were 94%. Sensitivity of antigen testing was 57% in proven and 58% in probable cases, ID antibody in 85% of proven and 75% of probable and antigen or ID antibody in 93% of proven and 95% of probable cases. Antigen was detected more often in disseminated (79%) than pulmonary cases (42%) as was ID antibody, 91% and 79%, respectively. Antigen testing was more sensitive in immunocompromised (76%) than non-immunocompromised patients (41%) while ID antibody was less sensitive in immunocompromised (74%) than in non-immunocompromised patients (93%). Combined antigen and ID antibody testing provided the highest sensitivity, 94% in all cases, 94% in immunocompromised and 95% in non-immunocompromised patients. Conclusion These findings support testing urine and serum for Coccidioides antigen and serum for ID antibodies for diagnosis of progressive pulmonary or disseminated coccidioidomycosis. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background Histoplasmosis (histo) is a common cause of invasive fungal infection in endemic regions and accurate diagnosis is difficult without direct tissue culture or pathology. Indirect fungal antigen testing for various fungal pathogens is typically performed to assist with diagnostic workup though cross-reaction can lead to difficulty interpreting results. We aimed to evaluate the prevalence of positive antigen testing for non- Histoplasma fungal pathogens in patients with proven invasive histo. Methods We performed a retrospective review of adult patients with proven invasive histo from 2010–2018 at our institution. For inclusion purposes, histo was confirmed by either fungal culture and/or cytology. Patient demographics, clinical characteristics and results of fungal antigen testing for Histoplasma, Blastomyces, Aspergillus , Cryptococcus and β- d -glucan were evaluated. Two different urine Histoplasma antigen assays were used during the study period. Results 57 (31%) of 182 patients diagnosed with histo during the study period had culture or cytology evidence of disease and were included in all further analysis. Thirty-two (56%) of these patients were male, 35 (61.4%) were Caucasian and the mean age was 50.1 years. HIV (20; 35%) and being on immunosuppressive medications (21, 37%) were common in this population. The majority of cases were classified as disseminated histo (40, 70%) followed by acute pulmonary (10; 18%) and chronic pulmonary (7, 12%) disease. Results of fungal antigen testing are documented in the table. Chi-squared analysis was performed. Conclusion There is a frequent cross reaction of non- Histoplasma fungal tests in patients with histo. In our review, there was a high rate of cross reaction with Blastomyces antigen, which can be confusing in regions where both pathogens coexist. Elevation of β- d -glucan was high in these patients. Urine Histoplasma antigen sensitivity was higher with MiraVista testing for disseminated disease in our review. While noninvasive fungal tests are helpful in diagnosis of these infrequent infections, clinicians must still maintain knowledge of the clinical differences between these fungal pathogens and be aware of the limitations of these tests. A prospective study is needed to better define differences between individual Histoplasma tests. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background Identifying Streptococcus pneumoniae (Sp) serotypes by urinary antigen detection assay (UAD) is the most sensitive and specific way to evaluate the changing epidemiology of non-bacteremic community-acquired pneumonia (CAP) and efficacy of pneumococcal vaccines. We first described an UAD to detect the Sp serotypes 1,-3,-4,-5,-6A,-6B,-7F,-9V,-14,-18C,-19A,-19F,-23F covered by the 13-valent Sp conjugate vaccine PCV13. To assess the pneumococcal disease burden of additional serotypes, a UAD-2 assay was developed to diagnose 11 additional Sp serotypes (-2,-8,-9N,-10A,-11A,-12F,-15B,-17F,-20,-22F,-33F). Methods UAD-2 specificity was achieved by capturing highly purified pneumococcal polysaccharides with serotype-specific monoclonal antibodies using Luminex technology. Assay qualification assessed accuracy, precision, and sample linearity. Serotype positivity was based on cutoffs determined by non-parametric statistical evaluation of urine samples from individuals without pneumococcal disease. Clinical sensitivity and specificity of the positivity cutoffs were assessed in a clinical validation. Results The UAD-2 was shown to be specific and reproducible. Clinical validation using urine samples from invasive disease patients demonstrated assay sensitivity and specificity of 92.2% and 95.9%, respectively compared with a gold standard of isolating and typing (by Quellung) Sp bacteria from patient samples. Analysis of 11,087 CAP patients showed a UAD-2 and UAD-1 serotype prevalence of 4.33% and 4.60%, respectively (bacteremic and non-bacteremic CAP combined). Conclusion The qualified/clinically validated UAD-2 method has applicability in understanding the epidemiology of nonbacteremic Sp CAP as well as assessing vaccine efficacy of future pneumococcal conjugate vaccines. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background Many emergency departments and urgent care settings use the commonly available Respiratory Syncytial Virus Rapid Antigen Detection Test (RSV RADT) to diagnose children with RSV. We noted discordant results between RADT and definitive testing. Our study looked at the positive predictive value (PPV) and the false discovery rate (FDR) of the RSV RADT at our facility. Methods We pro- and retrospectively reviewed all patients with positive RSV RAPD tests from July 1, 2017 through March 31, 2019. The test utilized was the QuickVue® RSV Test Kit (QUIDEL Corp, CA, USA), which detects the viral fusion protein present in RSV. Of the tests performed, we chose patients who had definitive testing with either a direct fluorescent antibody (DFA) or a polymerase chain reaction (PCR). We then calculated the PPV as well as the FDR of the RSV RADT during the total interval period, as well as off-season periods (April 1 through October 31) and in-season periods (November 1 through March 31). Results During the study period there were 1128 RSV RADT tests performed, of which 232 had definitive testing with either DFA or PCR (Figures 1 and 2). We found the overall PPV during the study period was 63.3%. During the off-season 30 positive RSV RADT received definitive testing, of which 6 were positive, which yields a PPV of only 20%. In season, 202 RSV RADT received additional testing with 141 positive for RSV. The PPV was 69.8%. The FDR correlated with 36.7% throughout the entire studied period, 80% during the off-season and 30.2% during in-season. As expected, the PPV was higher during times of higher prevalence (Figure 3). Conclusion Based on our results, utilization of the RSV RADT during time of low prevalence yields a high false detection rate and should therefore be discouraged. The use during times of high prevalence yields only modest results and is unlikely to aid in clinical decision-making. Our results differ from those published by the manufacturer (PPV 84%), and may reflect differences in sample collection in the acute care setting. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background Group A streptococcal (GAS) pharyngitis is common in the United States (US). Each year, approximately 12 million people seek medical care for pharyngitis, accounting for ~2% of ambulatory care visits. The gold standard method for diagnosing GAS is culture. However, because culture is time intensive, rapid antigen detection tests (RADTs), with or without culture confirmation, are commonly used. Although RADTs provide results quickly, test sensitivity has been shown to be sub-optimal, which can lead to inappropriate treatment decisions. Recently, highly sensitive point-of-care nucleic acid amplification tests (POC NAAT), such as the cobas® Liat® System, have emerged. The objective of this study was to evaluate the cost-effectiveness (CE) and budget impact (BI) of adopting POC NAAT compared with RADT+culture confirmation to diagnose GAS pharyngitis from the US third-party payer perspective. Methods A decision-tree economic model was developed in Microsoft Excel to quantify costs and clinical outcomes associated with POC NAAT and RADT+culture over a one-year period. All model inputs were derived from published literature and public databases. Model outputs included costs and clinical effects measured as quality-adjusted life days (QALDs) lost. One-way and probabilistic sensitivity analyses were performed to assess the impact of uncertainty on results. Results CE analysis showed that POC NAAT would cost $44 per patient compared with $78 with RADT+ culture. POC NAAT was associated with fewer QALDs lost relative to RADT+ culture. Therefore, POC NAAT may be considered the "dominant" strategy (i.e. lower costs and higher effectiveness). Findings were robust in sensitivity analyses. BI analysis showed that adopting POC NAAT for diagnosis of GAS could yield cost-savings of 0.3% vs. current budget over 3 years. This is due to savings associated with testing, GAS-related complications, antibiotic treatment and treatment-associated complication costs. Conclusion Results suggest that adopting POC NAAT to diagnose GAS would be considered cost-effective and yield cost-savings for US payers relative to RADT+culture. Access to POC NAAT would be important to optimize appropriate GAS diagnosis and treatment decisions. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

There are four distinct antigenic serotypes of dengue viruses (DENV-1-4). Sequential infections with different serotypes lead to cross-reactive but also serotype-specific neutralizing antibody responses. Neutralization assays are considered as gold standard for serotype-specific antibody detection. However, for retrospective seroprevalence studies, access to large serum quantities is limited making neutralization assays well-nigh impossible. Therefore, a serological test, wasting only 10 µL serum, was developed using fusion proteins of maltose binding protein and E protein domain 3 (MBP-ED3) as antigens. Twelve MBP-ED3 antigens for DENV-1-4, three MBP-ED3 antigens for WNV, JEV, and TBEV, and MBP were dotted onto a single nitrocellulose strip. ED3 dot assay results were compared to virus neutralization and ED3 ELISA test results, showing a >90% accordance for DENV-1 and a 100% accordance for DENV-2, making the test specifically useful for DENV-1/-2 serotype-specific antibody detection. Since 2010, DENV-1 has replaced DENV-2 as the dominant serotype in Cambodia. In a retrospective cohort analysis, sera collected during the DENV-1/-2 endemic period showed a shift to DENV-2-specific antibody responses in 2012 paralleled by the decline of DENV-2 infections. Altogether, the ED3 dot assay is a serum-, time- and money-saving diagnostic tool for serotype-specific antibody detection, especially when serum samples are limited. [ABSTRACT FROM AUTHOR]

Antigen-based immunoassays are currently needed for point-of-care quantification of Loa loa microfilariae (mf). Coupling transcriptomic approaches with bioinformatic analysis, we have identified 11 specific putative proteins (coding mRNAs) with potential utility as biomarkers of patent (mf + ) L. loa infection. We successfully developed antigen capture immunoassays to quantify 2 (LOAG&#95;14221 and LOAG&#95;15846) of these proteins in individual plasma/serum samples. Of the 2 quantifiable circulating biomarkers, LOAG&#95;14221 showed the highest degree of specificity, particularly with a monoclonal antibody-based immunoassay. Moreover, the levels of LOAG&#95;14221 in L. loa mf + patients were positively correlated to the mf densities in the corresponding blood samples ( r = 0.53 and P = 0.008 for polyclonal assay; r = 0.54 and P = 0.004 for monoclonal assay). Thus, LOAG&#95;14221 is a very promising biomarker that will be exploited in a quantitative point-of-care immunoassay for determination of L. loa mf densities., (Copyright © 2017 American Society for Microbiology.)