Rapid Influenza Diagnostic Tests Research Articles

Influenza A (H1N1) in Hospitalized Children.

Influenza A (H1N1) is a contagious respiratory infection caused by the influenza A virus. In the majority of cases, H1N1 influenza is benign. However, it can be dangerous for infants and children with underlying chronic diseases. The severity of influenza depends on various factors, including the virulence of the virus strain, preexisting immunity level, and individual health conditions. The aim of this study is to describe the clinical profile of H1N1 influenza in hospitalized infants and children. This is a prospective and descriptive study conducted from November 1, 2018, to January 31, 2024. In this study, we included all children under 14 years old hospitalized for suspected severe lower respiratory infection who had gone through virological testing. We used a multiplex polymerase chain reaction (PCR) kit: the Film Array-Respiratory Panel. Due to the depletion of multiplex PCR kits, this study continued using rapid influenza diagnostic tests based on immunochromatographic technique. We report 45 confirmed cases of H1N1 influenza, collected during the period from November 1, 2018, to January 31, 2024. The average age was 2 years and 4 months. The main reason for admission was respiratory distress found in all patients. In 53% of the cases, there was an associated comorbidity, including asthma (17 cases), prematurity (2 cases), congenital adrenal hyperplasia (2 cases), cystic fibrosis (1 case), undetermined etiology bronchial dilation (1 case), and Basedow's disease (1 case). The clinical presentation included viral bronchiolitis (17 cases), moderate asthma exacerbation (10 cases), severe asthma exacerbation (7 cases), pneumonia (9 cases), bronchial dilation exacerbation (1 case), and flu-like syndrome with adrenal insufficiency (1 case). Fever was present in 31 patients. Gastrointestinal symptoms such as diarrhea and vomiting were present in 20 cases. Three patients required intensive care, with 2 children being intubated and ventilated (one severe acute asthma and one severe viral bronchiolitis). Two cases were treated with oseltamivir. The average length of hospital stay was 7.5 days, ranging from 3 to 20 days. All cases showed favorable evolution. We conclude that preventive measures remain crucial, and influenza vaccination is highly recommended in cases of underlying morbidity.

Effectiveness of inactivated influenza vaccine in children during the 2023/24 season: The first season after relaxation of intensive COVID-19 measures

BackgroundThe annual administration of the influenza vaccine is the most effective method for preventing influenza. We have evaluated the effectiveness of the inactivated influenza vaccine in children aged 6 months to 15 years across the seasons from 2013/2014 to 2022/2023. This study aims to investigate the effectiveness of the inactivated influenza vaccine in the 2023/2024 season, the first year following the easing of strict COVID-19 measures, and possibly the last season when only the inactivated vaccine is available on the market. MethodsAdjusted vaccine effectiveness for the 2023/2024 season was assessed using a test-negative case-control design, with results based on polymerase chain reaction and rapid influenza diagnostic tests. Vaccine effectiveness was calculated by influenza type and patient hospitalization/outpatient status. ResultsA total of 1832 children were recruited. The inactivated influenza vaccine was effective in preventing both symptomatic influenza A and B in both inpatient and outpatient settings. Overall vaccine effectiveness for influenza A was 51% (95% confidence interval [CI], 23%–69%, n = 930) in inpatient settings and 54% (95%CI, 27%–71%, n = 559) in outpatient settings. For influenza B, effectiveness was 60% (95%CI, 22%–79%, n = 859) in inpatient settings and 56% (95%CI, 26%–74%, n = 558) in outpatient settings. Analysis suggested that administering two doses enhanced effectiveness specifically against influenza B. ConclusionsThis is the first study to demonstrate influenza vaccine effectiveness in children after the relaxation of strict COVID-19 measures in Japan (2023/2024). We recommend the current inactivated vaccine for preventing both influenza A and B in children, with consideration for the potential use of two doses to enhance effectiveness against influenza B.

Clinical characteristics and prognostic marker for hospitalization in children with influenza infection in an emergency setting

BackgroundInfluenza is a main cause of illnesses during seasonal outbreaks. Identifying children with influenza who may need hospitalization may lead to better influenza outcomes.ObjectiveTo identify factors associated with the severity of influenza infection, specifically among children who were admitted to the hospital after being diagnosed with influenza at the emergency department.MethodsA retrospective cohort study was conducted among pediatric patients (age < 18 years) with a positive influenza rapid test who visited the emergency department at Srinagarind hospital between January2015-December2019. The dependent variable was hospital admission, while the independent variables included clinical parameters, laboratory results, and emergency severity index(ESI). The association between these variables and hospital admission was analyzed.ResultsThere were 542 cases of influenza included in the study. The mean age was 7.50 ± 4.52 years. Males accounted for 52.4% of the cases. A total of 190(35.05%) patients, needed hospitalization. Patients with pneumonia, those who required hospitalization or were admitted to the critical care unit, consistently exhibited an elevated absolute monocyte count and a reduced lymphocyte-to-monocyte ratio (LMR). Various factors contribute to an increased risk for hospitalization, including ESI level 1–2, co-morbidity in patients, age < 1 year old, and an LMR below 2.ConclusionsESI level 1–2 and co-morbidity in patients represent significant risk factors that contribute to higher hospitalization admissions. A LMR below 2 can be used as a prognostic marker for hospitalization in children with influenza infection.

Prospective external validation of the FluScore risk score for influenza in outpatients.

Testing for influenza in patients with acute lower respiratory tract infection (LRTI) is common and in some cases is performed for all patients with LRTI. A more selective approach to testing could be more efficient. We used data from two prospective studies in the US primary and urgent care settings that enrolled patients with acute LRTI or influenza-like illness. Data were collected in the 2016, 2019, 2021, and 2022 flu seasons. All patients underwent polymerase chain reaction (PCR) testing for influenza and the FluScore was calculated based on patient-reported symptoms at their initial visit. The probability of influenza in each risk group was reported, as well as stratum-specific likelihood ratios (SSLRs) for each risk level. The prevalence of influenza within risk groups varied based on overall differences in flu seasons and populations. However, the FluScore exhibited consistent performance across various seasons and populations based on the SSLRs. The FluScore had a consistent SSLR range of 0.20 to 0.23 for the low-risk group, 0.63 to 0.99 for the moderate-risk group, and 1.46 to 1.67 for the high-risk group. The diagnostic odds ratio based on the midpoints of these ranges was 7.25. The FluScore could streamline patient categorization, identifying patients who could be exempted from testing, while identifying candidates for rapid influenza tests. This has the potential to be more efficient than a "one size fits all" test strategy, as it strategically targets the use of tests on patients most likely to benefit. It is potentially usable in a telehealth setting.

Clinical Presentation, Risk Factors, and Comparison of Laboratory Diagnostics for Seasonal Influenza Virus Among Cambodians From 2007 to 2020.

Despite its global significance, challenges associated with understanding the epidemiology and accurately detecting, measuring, and characterizing the true burden of seasonal influenza remain in many resource-poor settings. A prospective observational study was conducted in Cambodia at 28 health facilities between 2007 and 2020 utilizing passive surveillance data of patients presenting with acute undifferentiated febrile illness (AUFI) to describe the prevalence of influenza A and B and characterize associated risk factors and symptoms using a questionnaire. A comparison of rapid influenza diagnostic tests (RIDTs) and real-time reverse transcription polymerase chain reaction (rRT-PCR) results was also conducted. Of 30 586 total participants, 5634 (18.4%) tested positive for either influenza A or B, with 3557 (11.6%) positive for influenza A and 2288 (7.5%) positive for influenza B during the study. Influenza A and B were strongly associated with the rainy season (odds ratio [OR], 2.30; P < .001) and being from an urban area (OR, 1.45; P < .001). Analysis of individual symptoms identified cough (OR, 2.8; P < .001), chills (OR, 1.4; P < .001), and sore throat (OR, 1.4; P < .001) as having the strongest positive associations with influenza among patients with AUFI. Analysis comparing RIDTs and rRT-PCR calculated the overall sensitivity of rapid tests to be 0.492 (95% CI, 0.479-0.505) and specificity to be 0.993 (95% CI, 0.992-0.994) for both influenza type A and B. Findings from this 14-year study include describing the epidemiology of seasonal influenza over a prolonged time period and identifying key risk factors and clinical symptoms associated with infection; we also demonstrate the poor sensitivity of RIDTs in Cambodia.

Characterization of viral infections in children with influenza-like-illness during December 2018-January 2019.

Respiratory viral infection (RVI) is of very concern after the outbreak of COVID-19, especially in pediatric departments. Learning pathogen spectrum of RVI in children previous the epidemic of COVID-19 could provide another perspective for understanding RVI under current situation and help to prepare for the post COVID-19 infection control. A nucleic acid sequence-based amplification (NASBA) assay, with 19 pairs of primers targeting various respiratory viruses, was used for multi-pathogen screening of viral infections in children presenting influenza-like illness (ILI) symptoms. Children with ILI at the outpatient department of Beijing Tsinghua Changgung Hospital during the influenza epidemic from 12/2018 to 01/2019 were included. Throat swabs were obtained for both the influenza rapid diagnostic test (IRDT) based on the colloidal gold immunochromatographic assay and the NASBA assay, targeting various respiratory viruses with an integrated chip technology. Of 519 patients, 430 (82.9%) were positive in the NASBA assay. The predominant viral pathogens were influenza A H1N1 pdm1/2009 (pH1N1) (48.4%) and influenza A (H3N2) (18.1%), followed by human metapneumovirus (hMPV) (8.8%) and respiratory syncytial virus (RSV) (6.1%). Of the 320 cases identified with influenza A by NASBA, only 128 (40.0%) were positive in the IRDT. The IRDT missed pH1N1 significantly more frequently than A (H3N2) (P<0.01). Influenza A pH1N1 and A (H3N2) were the major pathogens in <6 years and 6-15 years old individuals respectively (P<0.05). In summary, influenza viruses were the major pathogens in children with ILI during the 2018-2019 winter influenza epidemic, while hMPV and RSV were non-negligible. The coexistence of multiple pathogen leading to respiratory infections is the normalcy in winter ILI cases.

Importance of History Taking and Physical Examination Before Rapid Laboratory Test for Seasonal Influenza Virus: A Single-Center Multiple Logistic Analysis.

Background Despite several rapid influenza diagnostic tests (RIDTs), they are predicting whether a patient has influenza before rapid testing is important. Here, we assessed factors predictive of a positive flu test via RIDTs by combining interviews and physical examination. Methods We analyzed the relationship between interviews and physical findings and results of RIDTs using multivariable logistic regression. Results Two hundred seventy-six children were enrolled throughout the 2018-2019 flu season. Accordingly, 115 patients (41.7%) were positive for flu A. Our logistic regression model identified age, body temperature, and the existence of upper respiratory symptoms as significant factors for predicting positive for RIDTs, with odds ratios (OR) of 1.17 [95% CI (confidence interval): 1.08-1.25]/+Δ1year old, 1.70 (95% CI: 1.27-2.27)/+Δ1 ℃, and 5.08 (95% CI: 2.57-10.00) for respiratory symptoms. In addition, the OR for sick contact was 7.67 (95% CI: 3.96-14.90). Our logistic regression model showed an area under the curve (AUC) of 0.84. History of vaccination was not identified as a significant factor in positive RIDTs. Conclusions The existence of sick contact was associated with a positive flu test via RIDTs. Although RIDTs are an easy and quick method for detecting the flu virus, we should perform the appropriate identification of cases for RIDTs by combining interviews and physical findings.

HLH Secondary to Influenza

Introduction Hemophagocytic lymphohistiocytosis (HLH) is a pathological condition characterized by excessive inflammation and tissue damage resulting from an aberrant immune system response. HLH can be classified into two distinct categories: primary HLH and secondary HLH. Secondary hemophagocytic lymphohistiocytosis (HLH) is an acquired condition that can be precipitated by various infections, malignancies, or rheumatological disorders. Herein, we present a rare case of HLH secondary to influenza B infection. Case Presentation A 37-year-old who routinely vapes and smokes cannabis presented to the emergency department with subjective fevers, body pains, fatigue, productive cough, shortness of breath, nausea, non-bloody, non-bilious vomiting, and watery diarrhea for one week. He was tachypneic, tachycardic, and febrile (101.1 F). He had loud bibasilar crackles on auscultation. Hb 14.8, total WBC 2.2, platelets 170, AKI with serum creatinine 1.9, and transaminitis with AST/ALT/ALP 130/56/122 U/L were the patient's initial lab results. Rapid influenza, strep, and COVID-19 antigen tests were negative. He exhibits hypoxemia with pH 7.46, pCO2 32.5, pO2 52.1, HCO3 22.9, and FIO2 40%. Urinalysis showed nonsignificant. CRP was 8.3 mg/dL. Negative procalcitonin. chest x-ray and ct showed bilateral diffuse patchy airspace infiltration, suggesting infectious process with mild pleaural effusion. In the critical care unit, he received Antibiotics and inhaled therapy for acute hypoxic respiratory failure with severe ARDS. After deteriorating, he was intubated. The respiratory pathogen panel detected Influenza B. Blood cultures and remaining pneumonia workup were negative. The lab results suggested HLH (table 1). Autoimmune tests were negative. Oseltamivir was given for 5 days. Repeat chest x-rays showed stable pulmonary infiltrates in the right middle and lower lobes, but the patient decompensated clinically with increasing ventilator requirements and dyssynchrony despite heavy sedation, paralytics, and proning and was transferred to a different hospital for ECMO evaluation on day 12. Discussion Primary and secondary HLH: Secondary HLH is caused by infections, malignancies, or rheumatological illnesses, while primary HLH is hereditary. The mortality outcome of HLH is extremely dependent on early detection and treatment 1. Due to the rarity of this disease entity, difficult diagnostic criteria, and concern for alternate diagnoses, internists may be less aware of it. Further complicating the diagnosis is the fact that the first bone marrow biopsy may not always show hemophagocytosis 2. This is why it is important to be cognizant of this diagnosis and it's diagnostic criteria. Our patient was suspected of HLH based on HScore for reactive hemophagocytic syndrome and the newest updated HLH diagnostic criteria (5 of 8 criteria should be met) 6. EBV is the most common viral infection which can cause HLH. CMV, Parvo, HSV, and H1N1 are other infections. HLH-Influenza B connection is poorly documented 7 Only one case of HLH induced by influenza B in a healthy patient was found in literature. To our knowledge, Our 38-year-old patient is the second known case of secondary HLH secondary to Influenza B in a healthy patient. Influenza B seldom causes HLH. This connection in adulthood is poorly researched. Patients with influenza virus infections have significant intestinal apoptosis and reactive hemophagocytic activity in bone marrow, lungs, and liver3. Influenza variants reduce CD8+ T cell cytotoxicity and perforin expression, likely causing HLH syndrome 4. A study suggests that virus-associated hemophagocytic syndrome (VAHS) is a common consequence of severe 2009 influenza A (H1N1) infection and contributes to multiorgan failure and mortality. 9 (36%) of 25 severely ill patients with confirmed 2009 influenza A (H1N1) infection developed VAHS, and 8 (89%) died 5. Conclusion: We present this case to raise awareness among physicians regarding the potential occurrence of hemophagocytic lymphohistiocytosis (HLH) as a complication in adult patients who present with influenza B virus infection accompanied by fever and pancytopenia. The aim is to emphasize the importance of considering HLH as a differential diagnosis in order to facilitate timely identification and initiation of appropriate treatment for this condition.

Symptomatic Differences between Influenza A/H3N2 and A/H1N1 in Korea.

Limited understanding exists regarding clinical distinctions between influenza A/H3N2 and A/H1N1 subtypes, particularly in primary health care. We conducted a comparative analysis of symptomatic characteristics of influenza subtypes in Korea. This retrospective study analyzed medical records of patients who presented with positive test results for influenza-like illness (rapid influenza diagnostic test; RIDT) during the H3N2-dominant 2016-2017 and H1N1-dominant 2018-2019 seasons. Symptomatic manifestations, contact history, vaccination history, and clinical course were analyzed between the two seasons. The most frequent symptom in the RIDT-positive patients was fever (80.1% and 79.1%, respectively). The average body temperature was higher, and the number of patients with high fever was greater in the H3N2-dominant season than in the H1N1-dominant season (p < 0.001). Conversely, other symptoms, such as myalgia, cough, and sore throat, were significantly more common in the H1N1-dominant season than in the H3N2-dominant season (p < 0.001). Antiviral drugs were prescribed to most febrile RIDT-positive patients (82.2% and 81.3%, respectively, p = 0.516). Analyzing primary care data revealed different clinical manifestations according to the subtype. Therefore, physicians should consider these variable hallmarks and employ tailored therapeutic strategies to reduce the complication rate.

Rapid Detection of Influenza Outbreaks in Long-Term Care Facilities Reduces Emergency Room Visits and Hospitalization: A Randomized Trial

ObjectivesTo assess whether the use of rapid influenza diagnostic tests (RIDTs) for long-term care facility (LTCF) residents with acute respiratory infection is associated with increased antiviral use and decreased health care utilization. DesignNonblinded, pragmatic, randomized controlled trial evaluating a 2-part intervention with modified case identification criteria and nursing staff–initiated collection of nasal swab specimen for on-site RIDT. Setting and ParticipantsResidents of 20 LTCFs in Wisconsin matched by bed capacity and geographic location and then randomized. MethodsPrimary outcome measures, expressed as events per 1000 resident-weeks, included antiviral treatment courses, antiviral prophylaxis courses, total emergency department (ED) visits, ED visits for respiratory illness, total hospitalizations, hospitalizations for respiratory illness, hospital length of stay, total deaths, and deaths due to respiratory illness over 3 influenza seasons. ResultsOseltamivir use for prophylaxis was higher at intervention LTCFs [2.6 vs 1.9 courses per 1000 person-weeks; rate ratio (RR) 1.38, 95% CI 1.24-1.54; P < .001]; rates of oseltamivir use for influenza treatment were not different. Rates of total ED visits (7.6 vs 9.8/1000 person-weeks; RR 0.78, 95% CI 0.64-0.92; P = .004), total hospitalizations (8.6 vs 11.0/1000 person-weeks; RR 0.79, 95% CI 0.67-0.93; P = .004), and hospital length of stay (35.6 days vs 55.5 days/1000 person-weeks; RR 0.64, 95% CI 0.0.59-0.69; P < .001) were lower at intervention as compared to control LTCFs. No significant differences were noted for respiratory-related ED visits or hospitalizations or in rates for all-cause or respiratory-associated mortality. Conclusions and ImplicationsThe use of low threshold criteria to trigger nursing staff–initiated testing for influenza with RIDT resulted in increased prophylactic use of oseltamivir. There were significant reductions in the rates of all-cause ED visits (22% decline), hospitalizations (21% decline), and hospital length of stay (36% decline) across 3 combined influenza seasons. No significant differences were noted in respiratory-associated and all-cause deaths between intervention and control sites.

Adequacy of using a single nasal swab for rapid influenza diagnostic testing, PCR, and whole genome sequencing.

Rapid influenza diagnostic tests (RIDT) demonstrate varying sensitivities, often necessitating reverse transcriptase polymerase chain reaction (RT-PCR) to confirm results. The two methods generally require separate specimens. Using the same anterior nasal swab for both RIDT and molecular confirmation would reduce cost and waste and increase patient comfort. The aim of this study was to determine if RIDT residual nasal swab (rNS) specimens are adequate for RT-PCR and whole genome sequencing (WGS). We performed RT-PCR and WGS on paired rNS and nasopharyngeal or oropharyngeal (NP/OP) swab specimens that were collected from primary care patients across all ages. We randomly selected 199 and 40 paired specimens for RT-PCR and WGS, respectively, from the 962 paired surveillance specimens collected during the 2014-2015 influenza season. Sensitivity and specificity for rNS specimens were 81.3% and 96.7%, respectively, as compared to NP/OP specimens. The mean cycle threshold (Ct) value for the NP/OP specimen was significantly lower when the paired specimens were both positive than when the NP/OP swab was positive and the nasal swab was negative (25.5 vs 29.5; p<0.001). Genomic information was extracted from all 40 rNS specimens and 37 of the 40 NP/OP specimens. Complete WGS reads were available for 67.5% (14 influenza A; 13 influenza B) of the rNS specimens and 59.5% (14 influenza A; 8 influenza B) of the NP/OP specimens. It is feasible to use a single anterior nasal swab for RIDT followed by RT-PCR and/or WGS. This approach may be appropriate in situations where training and supplies are limited. Additional studies are needed to determine if residual nasal swabs from other rapid diagnostic tests produce similar results.

POINT OF CARE PCR FOR INFLUENZA AND RESPIRATORY SYNCYTIAL VIRUS: FROM THE LAB TO THE EMERGENCY ROOM

RNA viruses, such as influenza and respiratory syncytial virus (RSV), are common causes of lower airway infections. Rapid tests (antigen-based by immunochromatographic and molecular technique - RIT and RMT, respectively) with good diagnostic accuracy directly impacts the quality of patient care and hospitalization costs. This study aims to evaluate the implementation of point of care PCR compared to rapid antigen-based tests for influenza and RSV in the emergency department.Methods: Prospective cross section study in an Emergency Room (ER) from August to September 2019, where all patients with influenza like illness went through RIT and RMT. The patients were divided in a model of four clinical scenarios to evaluate cost and isolation time in the ER.Results: 424 patients were included in the study. RIT showed sensitivity of only 40% compared with RMT (100% specificity; PPV 100%; NPV 68,7%), causing 103 patients to mistakenly leave respiratory isolation, raising biological risk in the ER. Fast results from RMT led negative patients to leave isolation early (262:10 less hours of isolation), allowing cost reduction of USD 1.921,20. Nonetheless, RMT had higher cost than RIT in all clinical scenarios with an increase of USD 12.788,90 (69,9% of cost related to tests and isolation precautions). Conclusion: RIT was a more affordable test but can’t be used to exclude disease and was associated with higher biological risk to the hospital setting. RMT had better diagnostic performance with faster results, allowing for less isolation time per patient tested.

Transmission dynamics of seasonal influenza in a remote island population

Seasonal influenza outbreaks remain an important public health concern, causing large numbers of hospitalizations and deaths among high-risk groups. Understanding the dynamics of individual transmission is crucial to design effective control measures and ultimately reduce the burden caused by influenza outbreaks. In this study, we analyzed surveillance data from Kamigoto Island, Japan, a semi-isolated island population, to identify the drivers of influenza transmission during outbreaks. We used rapid influenza diagnostic test (RDT)-confirmed surveillance data from Kamigoto island, Japan and estimated age-specific influenza relative illness ratios (RIRs) over eight epidemic seasons (2010/11 to 2017/18). We reconstructed the probabilistic transmission trees (i.e., a network of who-infected-whom) using Bayesian inference with Markov-chain Monte Carlo method and then performed a negative binomial regression on the inferred transmission trees to identify the factors associated with onwards transmission risk. Pre-school and school-aged children were most at risk of getting infected with influenza, with RIRs values consistently above one. The maximal RIR values were 5.99 (95% CI 5.23, 6.78) in the 7–12 aged-group and 5.68 (95%CI 4.59, 6.99) in the 4–6 aged-group in 2011/12. The transmission tree reconstruction suggested that the number of imported cases were consistently higher in the most populated and busy districts (Tainoura-go and Arikawa-go) ranged from 10–20 to 30–36 imported cases per season. The number of secondary cases generated by each case were also higher in these districts, which had the highest individual reproduction number (Reff: 1.2–1.7) across the seasons. Across all inferred transmission trees, the regression analysis showed that cases reported in districts with lower local vaccination coverage (incidence rate ratio IRR = 1.45 (95% CI 1.02, 2.05)) or higher number of inhabitants (IRR = 2.00 (95% CI 1.89, 2.12)) caused more secondary transmissions. Being younger than 18 years old (IRR = 1.38 (95%CI 1.21, 1.57) among 4–6 years old and 1.45 (95% CI 1.33, 1.59) 7–12 years old) and infection with influenza type A (type B IRR = 0.83 (95% CI 0.77, 0.90)) were also associated with higher numbers of onwards transmissions. However, conditional on being infected, we did not find any association between individual vaccination status and onwards transmissibility. Our study showed the importance of focusing public health efforts on achieving high vaccine coverage throughout the island, especially in more populated districts. The strong association between local vaccine coverage (including neighboring regions), and the risk of transmission indicate the importance of achieving homogeneously high vaccine coverage. The individual vaccine status may not prevent onwards transmission, though it may reduce the severity of infection.

Human rapid influenza diagnostic test: efficacy and significance for using in animal

Rapid influenza diagnostic tests (RIDTs) could considerably assist in clinical management resolving outbreaks of diseases in humans and animals. The RIDT for animals is rarely available and considerably expensive, especially in Thailand. In this study, therefore, the objective of this study was to determine the capacity of a commercial human RIDT “QuickNavi™Flu2”, an RIDT for influenza viruses A and B, to detect influenza viruses A antigen including 2 inactivated swine influenza viruses: H1N1 and H3N2, canine parainfluenza virus, and feline calicivirus. In addition, the efficacy of QuickNavi™Flu2 was compared with the real-time polymerase chain reaction assay (real-time rt-PCR). Both of SIV were used as stock solutions, and were serially diluted 6 concentrations before testing. The stock and diluted solutions of both SIV, specimens of canine parainfluenza virus, feline calicivirus and 96 unknown samples were tested by QuickNavi™Flu2 according to the guideline. Then all of samples were repeated testing with real-time rt-PCR assay. Results showed that Quick Navi-Flu could not give positive results for dilutions lower than 1:10 and 1:100, respectively. The sensitivity and specificity values of QuickNavi™Flu2 test in comparison to real-time rt-PCR assay for influenza A virus were 36.1% and 100%, respectively. In conclusion, a human RIDT can detect swine influenza H1N1 and H3N2 in high viral concentration, and appeared to be a useful tool for screening in animals when the viral load is sufficient.

The Influence of Rapid Influenza Diagnostic Testing on Clinician Decision-Making for Patients With Acute Respiratory Infection in Urgent Care.

The potential benefits of using rapid influenza diagnostic tests (RIDTs) in urgent care facilities for clinical care and prescribing practices are understudied. We compared antiviral and antibiotic prescribing, imaging, and laboratory ordering in clinical encounters with and without RIDT results. We compared patients with acute respiratory infection (ARI) symptoms who received an RIDT and patients who did not at 2 urgent care facilities. Primary analysis using 1-to-1 exact matching resulted in 1145 matched pairs to which McNemar 2 × 2 tests were used to assess the association between the likelihood of prescribing, imaging/laboratory ordering, and RIDT use. Secondary analysis compared the same outcomes using logistic regression among the RIDT-tested population between participants who tested negative (RIDT(-)) and positive (RIDT(+)). Primary analysis revealed that compared to the non-RIDT-tested population, RIDT(+) patients were more likely to be prescribed antivirals (OR, 10.23; 95% CI, 5.78-19.72) and less likely to be prescribed antibiotics (OR, 0.15; 95% CI, .08-.27). Comparing RIDT-tested to non-RIDT-tested participants, RIDT use increased antiviral prescribing odds (OR, 3.07; 95% CI, 2.25-4.26) and reduced antibiotic prescribing odds (OR, 0.52; 95% CI, .43-.63). Secondary analysis identified increased odds of prescribing antivirals (OR, 28.21; 95% CI, 18.15-43.86) and decreased odds of prescribing antibiotics (OR, 0.20; 95% CI, .13-.30) for RIDT(+) participants compared with RIDT(-). Use of RIDTs in patients presenting with ARI symptoms influences clinician diagnostic and treatment decision-making, which could lead to improved patient outcomes, population-level reductions in influenza burden, and a decreased threat of antibiotic resistance.

Results from a test-and-treat study for influenza among residents of homeless shelters in King County, WA: A stepped-wedge cluster-randomized trial.

Persons experiencing homelessness face increased risk of influenza as overcrowding in congregate shelters can facilitate influenza virus spread. Data regarding on-site influenza testing and antiviral treatment within homeless shelters remain limited. We conducted a cluster-randomized stepped-wedge trial of point-of-care molecular influenza testing coupled with antiviral treatment with baloxavir or oseltamivir in residents of 14 homeless shelters in Seattle, WA, USA. Residents ≥3 months with cough or ≥2 acute respiratory illness (ARI) symptoms and onset <7 days were eligible. In control periods, mid-nasal swabs were tested for influenza by reverse transcription polymerase chain reaction (RT-PCR). The intervention period included on-site rapid molecular influenza testing and antiviral treatment for influenza-positives if symptom onset was <48 h. The primary endpoint was monthly influenza virus infections in the control versus intervention periods. Influenza whole genome sequencing was performed to assess transmission and antiviral resistance. During 11/15/2019-4/30/2020 and 11/2/2020-4/30/2021, 1283 ARI encounters from 668 participants were observed. Influenza virus was detected in 51 (4%) specimens using RT-PCR (A = 14; B = 37); 21 influenza virus infections were detected from 269 (8%) intervention-eligible encounters by rapid molecular testing and received antiviral treatment. Thirty-seven percent of ARI-participant encounters reported symptom onset < 48 h. The intervention had no effect on influenza virus transmission (adjusted relative risk 1.73, 95% confidence interval [CI] 0.50-6.00). Of 23 influenza genomes, 86% of A(H1N1)pdm09 and 81% of B/Victoria sequences were closely related. Our findings suggest feasibility of influenza test-and-treat strategies in shelters. Additional studies would help discern an intervention effect during periods of increased influenza activity.

873. Comparison of Antibiotic and Antiviral Use before and after Deployment of Rapid Influenza Testing in the Emergency Department

Abstract Background Influenza shares common symptoms with bacterial pneumonia, resulting in inappropriate prescribing of antibiotics that may lead to increased risk of adverse reactions, antimicrobial resistance, and healthcare costs. Rapid influenza polymerase chain reaction (PCR) tests have reduced turnaround times compared to multiplex PCR respiratory panels allowing for earlier diagnosis, which may improve antimicrobial stewardship outcomes in the emergency department (ED). This study aims to compare antibiotic and antiviral use before and after deployment of a rapid influenza PCR in the ED. Methods This single-center, retrospective, cohort study included pediatric and adult patients discharged from the ED with a positive influenza test with either the multiplex PCR respiratory panel (January 2017 – July 2019) or rapid PCR (July 2019 – February 2020). The primary endpoint was antibiotic use pre- and post-implementation of the rapid influenza PCR in the ED. Secondary endpoints included antiviral use, duration of antimicrobial therapy, test turnaround time, ED length of stay, 30-day readmission, and adverse events. A multivariable regression model evaluated patient factors associated with antimicrobial prescribing. Results A total of 620 positive influenza results were identified with 280 patients (multiplex PCR = 33; rapid PCR = 247) meeting inclusion criteria. Patients were less likely to be prescribed antibiotics (39.4% vs 8.9%, OR 0.15, 95% CI 0.067–0.34) and more likely to be prescribed antivirals (24.2% vs 61.1%, OR 4.92, 95% CI 2.13–11.34) with the rapid influenza PCR. Rapid influenza PCR significantly reduced ED length of stay (4.9 vs 3.4 hours, p &amp;lt; 0.01) and test turnaround time (27 hours vs 3.5 hours, p &amp;lt; 0.01). Patients at high risk for complications associated with influenza were more likely to be prescribed antiviral therapy (25% vs 77.7%, OR 5.27, 95% CI 3.02–9.17). Based on the regression analysis conducted, asthma, (OR 3.5, 95% CI 1.48–8.26), immunosuppression (OR 9.6, 95% CI 1.18–78.2), and age less than 5 years old (OR 3.1, 95% CI 1.80–5.45) are predictors of antiviral prescribing. Conclusion Implementation of a rapid influenza PCR in the ED reduced antibiotic use and optimized antiviral therapy for patients at higher risk of influenza with complications. Disclosures All Authors: No reported disclosures.

A pragmatic randomized controlled trial of rapid on-site influenza and respiratory syncytial virus PCR testing in paediatric and adult populations

BackgroundRapid/point-of-care respiratory virus nucleic acid tests (NAT) may improve oseltamivir, antibiotic, diagnostic test, and hospital bed utilization. Previous randomized controlled trials (RCT) on this topic have not used standard procedures of an accredited healthcare and laboratory system.MethodsWe conducted a parallel RCT at two hospitals [paediatric = Alberta Children’s Hospital (ACH); primarily adult = Peter Lougheed Centre (PLC)]. Patients with a respiratory viral testing order were randomized to testing at either a central accredited laboratory (standard arm) or with a rapid polymerase chain reaction test at an on-site accredited laboratory followed by standard testing [rapid on-site test (ROST) arm] based on day of specimen receipt at the laboratory. Patients and clinicians were blinded to assignment.The primary outcome for ACH was inpatient length of stay (LOS) and for PLC was the proportion of inpatients prescribed oseltamivir.Results706 patient encounters were included at ACH; 322 assigned to ROST (181 inpatients) and 384 to the standard arm (194 inpatients). 422 patient encounters were included at PLC; 200 assigned to ROST (157 inpatients) and 222 to the standard arm (175 inpatients).The rate of oseltamivir prescription and number of doses given was reduced in PLC inpatients negative for influenza in the ROST arm compared to standard arm [mean 14.9% (95% CI 9.87–21.9) vs. 27.5% (21.0–35.2), p = 0.0135; mean 2.85 doses (SEM 2.39–3.32) vs. 4.17 doses (3.85–4.49) p = 0.022, respectively]. ROST also significantly reduced oseltamivir use at ACH, reduced chest radiographs (ACH), and laboratory test ordering (PLC), but not antibiotic prescriptions. ROST also reduced the median turnaround time by > 24 h (ACH and PLC).The LOS at ACH was not significantly different between the ROST and standard arms [median 4.05 days (SEM 1.79–18.2) vs 4.89 days (2.07–22.9), p = 0.062, respectively].No adverse events were reported.ConclusionsIn a RCT representing implementation of ROST in an accredited laboratory system, we found that a ROST improved oseltamivir utilization and is the first RCT to show reduced ancillary testing in both paediatric and adult populations. A larger study is required to assess reduction in paediatric LOS as ACH was underpowered. These findings help justify the implementation of rapid on-site respiratory virus testing for inpatients.Trial registration ISRCTN, number 10110119, Retrospectively Registered, 01/12/2021.

Features of the course of influenza and its co-infection in children at the present stage

Influenza is an acute respiratory infection, mainly affecting the respiratory tract (often the trachea), with a tendency to develop symptoms rapidly and in most cases not requiring hospitalization. All acute respiratory infections are non-specific, with symptoms of intoxication, catarrhal symptoms (nasal congestion, rhinorrhoea, sore throat or pharyngeal discomfort), fever and cough. Improvement and widespread implementation of molecular methods to identify respiratory pathogens has led to the establishment of a higher frequency of co-infections. A literature review of the frequency of influenza co-infections is presented. Clinical cases of monoinfluenza and co-infections of influenza and respiratory syncytial infection are described, demonstrating the antagonistic effect of the two viruses on the course of the disease. In the first case, the patient, 1 year 1 month old, was hospitalised with a fever of 39 ºC in a moderate condition. A nasopharyngeal swab showed RNA of influenza A virus by PCR and was diagnosed with influenza. In the second case, the patient, 2 years old, at the beginning of the disease complained of an increase in body temperature to 38.7 ºC, cough, and difficulty in nasal breathing. On admission, the patient was in moderate condition with a body temperature of 36.6 ºC, clear consciousness and well-being. On auscultation, breathing in the lungs was rigid, single moist rales, scattered on both sides. A nasopharyngeal swab showed RNA of influenza A virus and respiratory syncytial virus by PCR. A viral acute respiratory infection of combined etiology and acute bronchitis was diagnosed. In the third case, a 14-year-old patient presented with complaints of fever up to 39 ºC, headache, weakness, muscle pain, dry cough. The condition was of moderate severity. The diagnosis of influenza A was confirmed by a rapid test for influenza A/B/C. In the treatment and prevention of both monoinfection and co-infections of influenza and other viruses, these clinical examples demonstrate the effectiveness of oseltamivir. These clinical examples highlight some key parameters: respiratory co-infections change the typical clinical picture of the disease, making it difficult to clinically diagnose the infection, highlighting laboratory diagnosis, which in turn facilitates rapid verification of the diagnosis and timely prescription of adequate therapy.

Factors influencing sensitivity of a rapid influenza diagnostic test in a community-based population of kindergarten through 12th-grade students: Wisconsin 2015-2020.

Rapid influenza diagnostic tests (RIDTs) have variable sensitivity. In a community-based population of kindergarten through 12th-grade (K-12) students, we assessed factors that may influence RIDT performance using 2368 paired results from Sofia® influenza A + B fluorescent immunoassay and reverse transcription polymerase chain reaction (RT-PCR). RIDT sensitivity and specificity were 76.1% (95% CI: 72.8-79.1) and 97.2% (96.2-97.9), respectively. Factors associated with sensitivity included runny nose (OR =3.0, p< 0.001), nasal congestion (1.59, p= 0.045), days from symptom onset (per day; 0.75; p< 0.001), myalgia (0.61; p= 0.014), age (per 5years; 0.55; p= 0.001), and detection of another virus (0.50; p= 0.043). Understanding these factors can aid in interpreting negative results.