Failure of routine diagnostic methods to detect influenza in hospitalized older adults

Global, regional and national estimates of influenza-attributable ischemic heart disease mortality

BACKGROUND

Influenza virus infection is associated with incident ischemic heart disease (IHD) events. Here, we estimate the global, regional, and national IHD mortality burden attributable to influenza.

METHODS

We used vital registration data from deaths in adults ≥50 years (13.2 million IHD deaths as underlying cause) to assess the relationship between influenza activity and IHD mortality in a non-linear meta-regression framework from 2010 to 2019. This derived relationship was then used to estimate the global influenza attributable IHD mortality. We estimated the population attributable fraction (PAF) of influenza for IHD deaths based on the relative risk associated with a given level of weekly influenza test positivity rate and multiplied PAFs by IHD mortality from the Global Burden of Disease study.

FINDINGS

Influenza activity was associated with increased risk of IHD mortality across all countries analyzed. The mean PAF of influenza for IHD mortality was 3.9% (95% uncertainty interval [UI] 2.5-5.3%), ranging from <1% to 10%, depending on country and year. Globally, 299,858 IHD deaths (95% UI 191,216-406,809) in adults ≥50 years could be attributed to influenza, with the highest rates per 100,000 population in the Central Europe, Eastern Europe and Central Asia Region (32.3; 95% UI 20.6-43.8), and in the North Africa and Middle East Region (26.7; 95% UI 17-36.2).

INTERPRETATION

Influenza may contribute substantially to the burden of IHD. Our results suggest that if there were no influenza, an average of 4% of IHD deaths globally would not occur.

FUNDING

Collaborative study funded by Sanofi Vaccines.

Seasonal influenza, its complications and related healthcare resource utilization among people 60 years and older: A descriptive retrospective study in Japan

Evidence suggests that older people aged ≥65 years and those aged 60–64 years with chronic medical conditions are at higher risk of developing severe complications due to influenza virus infection when compared with young, healthy adults. Although seasonal influenza is monitored through a nationwide passive surveillance in Japan, influenza related outcomes and medical resource consumption have not been fully documented. This retrospective database study aimed to describe the epidemiological and clinical characteristics of medically attended influenza cases aged ≥60 years and the associated medical resource consumption in Japan. We used clinically diagnosed influenza (CDI) based on the international classification of disease codes, and laboratory-confirmed influenza (LCI) based on influenza test results, to identify the patient population during a total of nine seasons (2010/2011 to 2018/2019). A total of 372,356 CDI and 31,122 LCI cases were identified from 77 medical institutions. The highest numbers of medically-attended influenza episodes were in patients aged 65–74 years and 75–84 years. On average, across seasons, 5.9% of all-cause hospitalizations were attributable to CDI and 0.4% were LCI. Influenza viruses type A and B co-circulated annually in varying degree of intensity and were associated with similar level of complications, including cardiovascular-related. Oxygen therapy increased with age; by contrast, mechanical ventilation, dialysis, blood transfusion, and intensive care unit admission were higher in the younger groups. In-hospital mortality for inpatients aged ≥ 85 years with CDI and LCI were 18.6% and 15.5%, respectively. Considering the burden associated with medically-attended influenza in this population, influenza prevention, laboratory confirmation and clinical management should be emphasized by general practicians and specialists like cardiologists to protect this aging population.

Community-acquired pneumonia

Community-acquired pneumonia is not usually considered a high-priority problem by the public, although it is responsible for substantial mortality, with a third of patients dying within 1 year after being discharged from hospital for pneumoniae. Although up to 18% of patients with community-acquired pneumonia who were hospitalised (admitted to hospital and treated there) have at least one risk factor for immunosuppression worldwide, strong evidence on community-acquired pneumonia management in this population is scarce. Several features of clinical management for community-acquired pneumonia should be addressed to reduce mortality, morbidity, and complications related to community-acquired pneumonia in patients who are immunocompetent and patients who are immunocompromised. These features include rapid diagnosis, microbiological investigation, prevention and management of complications (eg, respiratory failure, sepsis, and multiorgan failure), empirical antibiotic therapy in accordance with patient's risk factors and local microbiological epidemiology, individualised antibiotic therapy according to microbiological data, appropriate outcomes for therapeutic switch from parenteral to oral antibiotics, discharge planning, and long-term follow-up. This Seminar offers an updated view on community-acquired pneumonia in adults, with suggestions for clinical and translational research.

Transient Atrioventricular Block as a Complication of Influenza A Virus: A Case Report

Influenza is one of the most common respiratory viral infections, causing annual epidemics of respiratory illnesses characterized by sudden onset of fever, malaise, myalgias, cough, and other respiratory complaints. A spectrum of cardiovascular complications has also been reported in association with influenza infection. Cardiovascular involvement can occur through the direct effects of the virus on the myocardium or through the exacerbation of the existing cardiovascular disease. We report the case of an 86-year-old woman without a history of cardiac disease before admission who developed a transient complete atrioventricular block without myocarditis after acute infection with the influenza A virus.

Evaluating an app-guided self-test for influenza: lessons learned for improving the feasibility of study designs to evaluate self-tests for respiratory viruses

Background

Seasonal influenza leads to significant morbidity and mortality. Rapid self-tests could improve access to influenza testing in community settings. We aimed to evaluate the diagnostic accuracy of a mobile app-guided influenza rapid self-test for adults with influenza like illness (ILI), and identify optimal methods for conducting accuracy studies for home-based assays for influenza and other respiratory viruses.

Methods

This cross-sectional study recruited adults who self-reported ILI online. Participants downloaded a mobile app, which guided them through two low nasal swab self-samples. Participants tested the index swab using a lateral flow assay. Test accuracy results were compared to the reference swab tested in a research laboratory for influenza A/B using a molecular assay.

Results

Analysis included 739 participants, 80% were 25–64 years of age, 79% female, and 73% white. Influenza positivity was 5.9% based on the laboratory reference test. Of those who started their test, 92% reported a self-test result. The sensitivity and specificity of participants’ interpretation of the test result compared to the laboratory reference standard were 14% (95%CI 5–28%) and 90% (95%CI 87–92%), respectively.

Conclusions

A mobile app facilitated study procedures to determine the accuracy of a home based test for influenza, however, test sensitivity was low. Recruiting individuals outside clinical settings who self-report ILI symptoms may lead to lower rates of influenza and/or less severe disease. Earlier identification of study subjects within 48 h of symptom onset through inclusion criteria and rapid shipping of tests or pre-positioning tests is needed to allow self-testing earlier in the course of illness, when viral load is higher.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06314-1.

A CT radiomics analysis of COVID-19-related ground-glass opacities and consolidation: Is it valuable in a differential diagnosis with other atypical pneumonias?

PURPOSE

To evaluate the discrimination of parenchymal lesions between COVID-19 and other atypical pneumonia (AP) by using only radiomics features.

METHODS

In this retrospective study, 301 pneumonic lesions (150 ground-glass opacity [GGO], 52 crazy paving [CP], 99 consolidation) obtained from nonenhanced thorax CT scans of 74 AP (46 male and 28 female; 48.25±13.67 years) and 60 COVID-19 (39 male and 21 female; 48.01±20.38 years) patients were segmented manually by two independent radiologists, and Location, Size, Shape, and First- and Second-order radiomics features were calculated.

RESULTS

Multiple parameters showed significant differences between AP and COVID-19-related GGOs and consolidations, although only the Range parameter was significantly different for CPs. Models developed by using the Bayesian information criterion (BIC) for the whole group of GGO and consolidation lesions predicted COVID-19 consolidation and AP GGO lesions with low accuracy (46.1% and 60.8%, respectively). Thus, instead of subjective classification, lesions were reclassified according to their skewness into positive skewness group (PSG, 78 AP and 71 COVID-19 lesions) and negative skewness group (NSG, 56 AP and 44 COVID-19 lesions), and group-specific models were created. The best AUC, accuracy, sensitivity, and specificity were respectively 0.774, 75.8%, 74.6%, and 76.9% among the PSG models and 0.907, 83%, 79.5%, and 85.7% for the NSG models. The best PSG model was also better at predicting NSG lesions smaller than 3 mL. Using an algorithm, 80% of COVID-19 and 81.1% of AP patients were correctly predicted.

CONCLUSION

During periods of increasing AP, radiomics parameters may provide valuable data for the differential diagnosis of COVID-19.

Analytical evaluation of the microarray-based FluChip-8G Influenza A+B Assay

BACKGROUND

Influenza causes a significant annual disease burden, with characterization of the infecting virus important in clinical and public health settings. Rapid immunoassays are fast but insensitive, whereas real-time RT-PCR is sensitive but susceptible to genetic mutations and often requires multiple serial assays. The FluChip-8G Influenza A+B Assay provides type and subtype/lineage identification of influenza A and B, including non-seasonal A viruses, in a single microarray-based assay with same day turnaround time.

OBJECTIVE

To evaluate key analytical performance characteristics of the FluChip-8G Influenza A+B Assay.

STUDY DESIGN

Analytical sensitivity, cross-reactivity, and multi-site reproducibility were evaluated.

RESULTS

The limit of detection (LOD) for the FluChip-8G influenza A+B Assay ranged from 5.8 × 10²-1.5 × 10⁵ genome copies/mL, with most samples ∼2 × 10³ genome copies/mL (∼160 genome copies/reaction). Fifty two (52) additional strains were correctly identified near the LOD, demonstrating robust reactivity. Two variant viruses (H1N1v and H3N2v) resulted in dual identification as both "non-seasonal influenza A" and A/H1N1pdm09. No reproducible cross-reactivity was observed for the 34 organisms tested, however, challenges with internal control inhibition due to crude growth matrix were observed. Lastly, samples tested near the LOD showed high reproducibility (97.0% (95% CI 94.7-98.7)) regardless of operator, site, reagent lot, or testing day.

CONCLUSION

The FluChip-8G Influenza A+B Assay is an effective new method for detecting and identifying both seasonal and non-seasonal influenza viruses, as revealed by good sensitivity and robust reactivity to 52 unique strains of influenza virus. In addition, the lack of cross-reactivity to non-influenza pathogens and high lab-to-lab reproducibility highlight the analytical performance of the assay as an alternative to real-time RT-PCR and sequencing-based assays. Clinical validation of the technology in a multi-site clinical study is the subject of a separate investigation.

Comparison of Cepheid® Xpert Flu and Roche RealTime Ready Influenza A/H1N1 Detection Set for detection of influenza A/H1N1

Objective

To compare two influenza polymerase chain reaction (PCR) methods.

Methods

A total of 749 suspected MERS-CoV patients presenting at Johns Hopkins Aramco Healthcare, Saudi Arabia, each submitted a clinical sample for influenza A reflex testing using the on-site Cepheid® Xpert Flu assay and at the Ministry of Health laboratory by the Roche PCR assay.

Results

There was 92.12% overall agreement between the two methods. Specificity of the Cepheid® Xpert Flu was 95.8% for H1N1 and 94.4% for total influenza A. Cepheid® Xpert Flu sensitivity for influenza A was 100% for younger patients (0–19-year age group) but significantly lower both for older patients (68.2% for 60–79-year and 50% for ≥80-year age groups) and overall for males compared to females (72.6% and 94.0%, respectively).

Conclusions

Specificity of the Cepheid® Xpert Flu test was high; however, sensitivity for total influenza A was lower particularly in males and older patients.

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92.12% agreement between assays for FluA/FluA (H1N1) pdm09 detection

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Specificity of FluA/FluA (H1N1) pdm09 detection high for Cepheid assay

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Sensitivity of total FluA detection significantly lower in males and older patients

Underdiagnosis of Influenza Virus Infection in Hospitalized Older Adults

OBJECTIVES

To describe factors associated with provider-ordered influenza testing in hospitalized older adults.

DESIGN

Information on participant demographics, symptoms, and provider-ordered influenza testing were collected by questionnaire and chart review. We conducted prospective laboratory-based surveillance using reverse-transcriptase polymerase chain reaction (RT-PCR), the criterion standard for diagnosis of influenza, to determine how participant characteristics and provider-ordered testing affected accurate influenza diagnosis.

SETTING

One academic and three community hospitals in Davidson County, Tennessee.

PARTICIPANTS

Adults aged 18 and older with acute respiratory illness or nonlocalizing fever (N=1,422).

MEASUREMENTS

We compared characteristics of participants with and without provider-ordered testing for influenza using the Wilcoxon test and Pearson chi-square test. Multivariable logistic regression models were used to identify factors predictive of provider-ordered influenza testing.

RESULTS

Twenty-eight percent (399/1,422) of participants had provider-ordered influenza testing. Participants who were tested were younger than those not tested (58 ± 18 vs 66 ± 15, p<.001) and more likely to have influenza-like illness (ILI) (71% vs 49%, p<.001). ILI decreased with increasing age (aged 18-49, 63%; aged 50-64, 60%; aged ≥65, 48%). ILI and younger age were independent predictors of provider-ordered testing. Of the 136 participants with influenza confirmed using RT-PCR, ILI was the only significant predictor of provider-ordered testing (adjusted odds ratio=3.43, 95% confidence interval=1.22-9.70).

CONCLUSION

Adults aged 65 and older hospitalized with fever or respiratory symptoms during influenza season are less likely to undergo a provider-ordered influenza test than younger adults. Some, but not all, of this disparity is due to a lower likelihood of ILI. Further strategies are needed to increase clinician awareness and testing in this vulnerable group.

Sensitive Diagnostics Confirm That Influenza C is an Uncommon Cause of Medically Attended Respiratory Illness in Adults

Among 4200 adults who presented with acute respiratory symptoms at a variety of medical practice settings (November 2006 through May 2012), only 13 (0.3%) nasal/throat swabs were positive for influenza C. Influenza C was rarely associated with medical care visits in adults.

Influenza in Older Adults

Annually, influenza viruses cause significant disease in older adults, varying with the virulence of the circulating strain, prior exposure to circulating strain, and influenza vaccine effectiveness. Older adults often present atypically (eg, without fever) and with complications of influenza infection such as chronic obstructive pulmonary disease and congestive heart failure exacerbations. Prevention methods include antiviral medications and vaccines. Current influenza vaccines have moderate effectiveness for the prevention of hospitalization, but newer more immunogenic vaccines designed for adults 65 years of age and older have been licensed.

Evaluation of the point-of-care Becton Dickinson Veritor™ Rapid influenza diagnostic test in Kenya, 2013-2014

BACKGROUND

We evaluated the performance of the Becton Dickinson Veritor™ System Flu A + B rapid influenza diagnostic test (RIDT) to detect influenza viruses in respiratory specimens from patients enrolled at five surveillance sites in Kenya, a tropical country where influenza seasonality is variable.

METHODS

Nasal swab (NS) and nasopharyngeal (NP)/oropharyngeal (OP) swabs were collected from patients with influenza like illness and/or severe acute respiratory infection. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the RIDT using NS specimens were evaluated against nasal swabs tested by real time reverse transcription polymerase chain reaction (rRT-PCR). The performance parameter results were expressed as 95% confidence intervals (CI) calculated using binomial exact methods, with P < 0.05 considered significant. Two-sample Z tests were used to test for differences in sample proportions. Analysis was performed using SAS software version 9.3.

RESULTS

From July 2013 to July 2014, 3,569 patients were recruited, of which 78.7% were aged <5 years. Overall, 14.4% of NS specimens were influenza-positive by RIDT. RIDT overall sensitivity was 77.1% (95% CI 72.8-81.0%) and specificity was 94.9% (95% CI 94.0-95.7%) compared to rRT-PCR using NS specimens. RIDT sensitivity for influenza A virus compared to rRT-PCR using NS specimens was 71.8% (95% CI 66.7-76.4%) and was significantly higher than for influenza B which was 43.8% (95% CI 33.8-54.2%). PPV ranged from 30%-80% depending on background prevalence of influenza.

CONCLUSION

Although the variable seasonality of influenza in tropical Africa presents unique challenges, RIDTs may have a role in making influenza surveillance sustainable in more remote areas of Africa, where laboratory capacity is limited.

Improving Accuracy of Influenza-Associated Hospitalization Rate Estimates

Adjusting for diagnostic test sensitivity enables more accurate and timely comparisons over time.

Diagnostic test sensitivity affects rate estimates for laboratory-confirmed influenza–associated hospitalizations. We used data from FluSurv-NET, a national population-based surveillance system for laboratory-confirmed influenza hospitalizations, to capture diagnostic test type by patient age and influenza season. We calculated observed rates by age group and adjusted rates by test sensitivity. Test sensitivity was lowest in adults >65 years of age. For all ages, reverse transcription PCR was the most sensitive test, and use increased from <10% during 2003–2008 to ≈70% during 2009–2013. Observed hospitalization rates per 100,000 persons varied by season: 7.3–50.5 for children <18 years of age, 3.0–30.3 for adults 18–64 years, and 13.6–181.8 for adults >65 years. After 2009, hospitalization rates adjusted by test sensitivity were ≈15% higher for children <18 years, ≈20% higher for adults 18–64 years, and ≈55% for adults >65 years of age. Test sensitivity adjustments improve the accuracy of hospitalization rate estimates.

Performance of rapid SOFIA Influenza A+B test compared to Luminex x-TAG respiratory viral panel assay in the diagnosis of influenza A, B, and subtype H3

Influenza is an acute respiratory illness caused by influenza A or B viruses that occur in outbreaks, mainly during the winter season. Rapid laboratory diagnosis of influenza can help guide the clinical management of suspected patients effectively. Clinical sensitivities and specificities of the rapid influenza diagnostic tests have varied considerably in the literature. Most of these studies are evaluated using previously frozen or stored specimens that had previously tested positive. This study compares the performance of the rapid SOFIA Influenza A+B test to nucleic acid multiplex test x-TAG respiratory viral panel (RVP) assay in freshly collected nasal aspirates and measured simultaneously by both assays. Retrospective data from 1649 nasal aspirates (September 2014 to May 2015) collected from adults as well as from children tested simultaneously by both rapid SOFIA Influenza A+B FIA immunofluorescence (Quidel, San Diego, CA) and qualitative nucleic acid multiplex RVP assay X-TAG Luminex technology (Luminex, Austin, Texas, USA) were analyzed. Concordance, and analytical sensitivity and specificity were evaluated for influenza A, subtypes H1 and H3, and influenza B. Prevalence for influenza A by RVP was 15%, for subtype H3 it was 11.2%, and for influenza B, 2.9%. None of the aspirates were positive for influenza A subtype H1. SOFIA Influenza rapid test demonstrated good specificity and low sensitivity compared with a nucleic acid test for influenza A, subtype H3, and for influenza B. SOFIA Influenza A + B test performed well in providing a rapid diagnosis, however, confirmatory molecular testing is recommended for negative test results. Re-evaluation of test performance should be periodically carried out during outbreaks with the emergence and circulation of new influenza strains.

Survey of influenza and other respiratory viruses diagnostic testing in US hospitals, 2012-2013

Background

Little is known about laboratory capacity to routinely diagnose influenza and other respiratory viruses at clinical laboratories and hospitals.

Aims

We sought to assess diagnostic practices for influenza and other respiratory virus in a survey of hospitals and laboratories participating in the US Influenza Hospitalization Surveillance Network in 2012–2013.

Materials and Methods

All hospitals and their associated laboratories participating in the Influenza Hospitalization Surveillance Network (FluSurv‐NET) were included in this evaluation. The network covers more than 80 counties in 15 states, CA, CO, CT, GA, MD, MN, NM, NY, OR, TN, IA, MI, OH, RI, and UT, with a catchment population of ~28 million people. We administered a standardized questionnaire to key personnel, including infection control practitioners and laboratory departments, at each hospital through telephone interviews.

Results

Of the 240 participating laboratories, 67% relied only on commercially available rapid influenza diagnostic tests to diagnose influenza. Few reported the availability of molecular diagnostic assays for detection of influenza (26%) and other viral pathogens (≤20%) in hospitals and commercial laboratories.

Conclusion

Reliance on insensitive assays to detect influenza may detract from optimal clinical management of influenza infections in hospitals.

Influenza in the Emergency Department: Vaccination, Diagnosis, and Treatment: Clinical Practice Paper Approved by American Academy of Emergency Medicine Clinical Guidelines Committee

BACKGROUND

Influenza is an acute respiratory virus that results in significant worldwide morbidity and mortality each year. As emergency physicians, we are often the first to encounter patients with seasonal influenza. It is therefore critical that we draw on the most recent and relevant research when we make clinical decisions regarding the diagnosis, treatment, and prophylaxis of this disease.

METHODS

A MEDLINE literature search from August 2009 to August 2015 was performed using the keywords influenza vaccination efficacy AND systematic, influenza AND rapid antigen testing, and Oseltamivir AND systematic, while limiting the search to human studies written in the English language. General review articles and case reports were omitted. Each of the selected articles then underwent a structured review.

RESULTS

We identified 163 articles through our literature search, of which 68 were found to be relevant to our clinical questions. These studies then underwent a rigorous review from which recommendations were given.

CONCLUSIONS

Influenza vaccine efficacy continues to range between 40% and 80%. Vaccination has the potential to decrease disease severity and is recommended for individuals older than 6 months of age. If resources permit, vaccination can be offered to patients presenting to the emergency department. Rapid antigen detection for influenza is a simple bedside test with high specificity, but generally low sensitivity. If a patient presents with a syndrome consistent with influenza and has negative rapid antigen detection, they should either receive a confirmatory reverse transcriptase polymerase chain reaction or be treated as if they have influenza. Treatment with neuraminidase inhibitors can decrease the duration of influenza and is recommended in hospitalized patients, or in those with high risk of complications.

Antiviral treatment among older adults hospitalized with influenza, 2006-2012

Objective

To describe antiviral use among older, hospitalized adults during six influenza seasons (2006—2012) in Davidson County, Tennessee, USA.

Methods

Among adults ≥50 years old hospitalized with symptoms of respiratory illness or non-localizing fever, we collected information on provider-initiated influenza testing and nasal/throat swabs for influenza by RT-PCR in a research laboratory, and calculated the proportion treated with antivirals.

Results

We enrolled 1753 adults hospitalized with acute respiratory illness. Only 26% (457/1753) of enrolled patients had provider-initiated influenza testing. Thirty-eight patients had a positive clinical laboratory test, representing 2.2% of total patients and 8.3% of tested patients. Among the 38 subjects with clinical laboratory-confirmed influenza, 26.3% received antivirals compared to only 4.5% of those with negative clinical influenza tests and 0.7% of those not tested (p<0.001). There were 125 (7.1%) patients who tested positive for influenza in the research laboratory. Of those with research laboratory-confirmed influenza, 0.9%, 2.7%, and 2.8% received antivirals (p=.046) during pre-pandemic, pandemic, and post-pandemic influenza seasons, respectively. Both research laboratory-confirmed influenza (adjusted odds ratio [AOR] 3.04 95%CI 1.26-7.35) and clinical laboratory-confirmed influenza (AOR 3.05, 95%CI 1.07-8.71) were independently associated with antiviral treatment. Severity of disease, presence of a high-risk condition, and symptom duration were not associated with antiviral use.

Conclusions

In urban Tennessee, antiviral use was low in patients recognized to have influenza by the provider as well as those unrecognized to have influenza. The use of antivirals remained low despite recommendations to treat all hospitalized patients with confirmed or suspected influenza.

Estimating influenza disease burden from population-based surveillance data in the United States

Annual estimates of the influenza disease burden provide information to evaluate programs and allocate resources. We used a multiplier method with routine population-based surveillance data on influenza hospitalization in the United States to correct for under-reporting and estimate the burden of influenza for seasons after the 2009 pandemic. Five sites of the Influenza Hospitalization Surveillance Network (FluSurv-NET) collected data on the frequency and sensitivity of influenza testing during two seasons to estimate under-detection. Population-based rates of influenza-associated hospitalization and Intensive Care Unit admission from 2010-2013 were extrapolated to the U.S. population from FluSurv-NET and corrected for under-detection. Influenza deaths were calculated using a ratio of deaths to hospitalizations. We estimated that influenza-related hospitalizations were under-detected during 2010-11 by a factor of 2.1 (95%CI 1.7-2.9) for age < 18 years, 3.1 (2.4-4.5) for ages 18-64 years, and 5.2 (95%CI 3.8-8.3) for age 65+. Results were similar in 2011-12. Extrapolated estimates for 3 seasons from 2010-2013 included: 114,192-624,435 hospitalizations, 18,491-95,390 ICU admissions, and 4,915-27,174 deaths per year; 54-70% of hospitalizations and 71-85% of deaths occurred among adults aged 65+. Influenza causes a substantial disease burden in the U.S. that varies by age and season. Periodic estimation of multipliers across multiple sites and age groups improves our understanding of influenza detection in sentinel surveillance systems. Adjusting surveillance data using a multiplier method is a relatively simple means to estimate the impact of influenza and the subsequent value of interventions to prevent influenza.

Respiratory syncytial virus- and human metapneumovirus-associated emergency department and hospital burden in adults

Objective

Determine the burden of illness associated with respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) in adults, especially young adults.

Design

Prospective surveillance study using RT-PCR for the diagnosis of RSV and HMPV.

Setting

One academic Emergency Department (ED), one academic hospital and three middle Tennessee community hospitals.

Sample

We prospectively enrolled Middle Tennessee residents ≥18 years old evaluated in the emergency department (ED) or hospitalized for respiratory symptoms May 2009 through April 2010. We collected nose/throat specimens for RSV and HMPV reverse-transcriptase polymerase chain reaction (RT-PCR) testing and obtained demographic and clinical data.

Main outcome Measures

Rates of ED visits and hospitalizations were calculated using the proportion of enrolled patients positive for each virus multiplied by the number of Middle Tennessee residents evaluated in EDs and/or hospitalized in Tennessee for acute respiratory illness during the study period.

Results

Three thousand two hundred and fifty six patients were eligible; 1477 (45·4%) were enrolled; 1248 (84·5%) of these consented to additional testing and had adequate samples. RT-PCR identified 32 (2·6%) patients with RSV and 33 (2·6%) with HMPV. The median duration of symptoms before ED presentation was 3·3 days with RSV and 2·8 days with HMPV, and before hospital admission was 4·5 days with RSV and 3·5 days with HMPV. The annual hospitalization and ED visit rates were similar for RSV and HMPV. The hospitalization rate associated with each virus was about 10 per 10 000 persons aged ≥50 years; ED rates were approximately 2 times higher. Hospitalization rates were about 2 per 10 000 persons aged 18–49 years, with ED rates 5–6 times higher.

Conclusion

RSV and MPV are associated with substantial disease in adults, with hospitalization and ED visits rates increasing with age.

Influenza infection screening tools fail to accurately predict influenza status for patients during pandemic H1N1 influenza season

BACKGROUND

Following the severe acute respiratory syndrome outbreak in 2003, hospitals have been mandated to use infection screening questionnaires to determine which patients have infectious respiratory illness and, therefore, require isolation precautions. Despite widespread use of symptom-based screening tools in Ontario, there are no data supporting the accuracy of these screening tools in hospitalized patients.

OBJECTIVE

To measure the performance characteristics of infection screening tools used during the H1N1 influenza season.

METHODS

The present retrospective cohort study was conducted at The Ottawa Hospital (Ottawa, Ontario) between October and December, 2009. Consecutive inpatients admitted from the emergency department were included if they were ≥18 years of age, underwent a screening tool assessment at presentation and had a most responsible diagnosis that was cardiac, respiratory or infectious. The gold-standard outcome was laboratory diagnosis of influenza.

RESULTS

The prevalence of laboratory-confirmed influenza was 23.5%. The sensitivity and specificity of the febrile respiratory illness screening tool were 74.5% (95% CI 60.5% to 84.8%) and 32.7% (95% CI 25.8% to 40.5%), respectively. The sensitivity and specificity of the influenza-like illness screening tool were 75.6% (95% CI 61.3% to 85.8%) and 46.3% (95% CI 38.2% to 54.7%), respectively.

CONCLUSIONS

The febrile respiratory illness screening tool missed 26% of active influenza cases, while 67% of noninfluenza patients were unnecessarily placed under respiratory isolation. Results of the present study suggest that infection-control practitioners should re-evaluate their strategy of screening patients at admission for contagious respiratory illness using symptom- and sign-based tests. Future efforts should focus on the derivation and validation of clinical decision rules that combine clinical features with laboratory tests.

Clinical diagnosis of pandemic A(H1N1) 2009 influenza in children with negative rapid influenza diagnostic test by lymphopenia and lower C-reactive protein levels

Background

The sensitivity of rapid influenza diagnostic test (RIDT) of children with influenza-like illness (ILI) remains low.

Objective

We compare the parameters between pandemic A(H1N1) 2009 influenza with negative RIDT and ILI not H1N1 for improving the low sensitivity of RIDT for children with ILI.

Methods

In a cohort of consecutive laboratory-confirmed H1N1 influenza, we identified 150 H1N1 children with positive RIDT, 152 H1N1 children with negative RIDT, and 75 children with ILI not H1N1. Viral load in throat, complete blood count (CBC), and C-reactive protein (CRP) levels between H1N1 children with negative RIDT and children with ILI not H1N1 were assessed.

Results

The diagnostic sensitivity of the RIDT was 45·5%. An analysis of CBC and CRP levels indicated that H1N1 children with negative RIDT had lower total leukocyte, neutrophil, lymphocyte, and basophil counts, and serum CRP levels (P < 0·01). Lymphocyte counts less than 1500 cells/mm³ and CRP levels <15 mg/l, determined by a receiver operating characteristic curve, showed a diagnostic sensitivity of 52·5% and 80·7%, respectively. Combining the lymphocyte counts and CRP levels provided a diagnostic sensitivity of 91·5%. Moreover, H1N1 children with negative RIDT had a lower viral load than those with positive RIDT (3·33 versus 4·48 log₁₀ copies/ml, P < 0·001); the viral load was negatively correlated to the lymphocyte count (P < 0·001).

Conclusions

A combination of a low lymphocyte count and a low CRP level could, in the early disease phase, provide a useful screening for H1N1 children with false-negative RIDT, potentially facilitating differential diagnoses.

Evaluation of a proximity extension assay for the detection of H1 2009 pandemic influenza viruses

The rapid influenza diagnostic tests (RIDTs) are widely distributed, simple to use, but often lack sensitivity as compared to gold standard methods (viral culture and nucleic acid detection technologies). Applying RIDTs outside of epidemic or pandemic infections results in large numbers of false negatives. Hence, a sensitive RIDT that would reduce the number of false negatives would result in an increased clinical value. We evaluated the potential of a proximity extension assay (PEA) for the detection of influenza A H1 viruses. This technology makes use of antibodies to capture the pathogen, followed by molecular detection. Forty-seven nasopharyngeal swab samples, all confirmed infections of the H1 2009 pandemic influenza virus, were evaluated. The performance of PEA was compared to the RIDT Quickvue Influenza A+B assay. The success rate of the comparative assays was modeled by means of a binary logistic response model. Both assays performed equally well within the current range of viral particles, expressed as log10 copies/ml. When the actual input of viral particles was taken into account, the 95% hitrate of PEA lies within the range of 4.60-7.02 log10 copies/reaction, which is an almost 2 log10 sensitivity improvement over the 95% hitrate of the Quickvue RIDT, ranging from 6.86 to 9.37 log10 copies/reaction. The PEA method holds promise to improve sensitive detection of influenza viruses in clinical samples.

Detection of influenza A and B viruses with the Sofia analyzer: a novel, rapid immunofluorescence-based in vitro diagnostic device

This report describes the clinical evaluation of a novel fluorescent immunoassay (FIA), Sofia Influenza A+B FIA (Quidel, San Diego, CA), for the rapid detection and differentiation of influenza A and B viruses. A total of 2,047 subjects provided nasal swabs and nasopharyngeal swabs or aspirates. The overall sensitivity and specificity for influenza A virus vs virus culture were 94% and 95%, respectively, and for influenza B virus were 89% and 96%, respectively. Fourteen hundred and sixty-one specimens were available for testing with reverse transcriptase-polymerase chain reaction (RT-PCR). The sensitivity of the Sofia Influenza A+B FIA for detecting influenza A and B viruses compared with the RT-PCR method was 78% and 86%, respectively. A high percentage of the positive specimens had low cycle threshold values, and almost all of these were positive with the Sofia test. This high level of sensitivity demonstrates that the Sofia influenza A+B FIA could improve the usefulness of rapid influenza virus testing.

Estimating influenza incidence and rates of influenza-like illness in the outpatient setting

Please cite this paper as: Fowlkes et al. (2012) Estimating influenza incidence and rates of influenza‐like illness in the outpatient setting. Influenza and Other Respiratory Viruses DOI: 10.1111/irv.12014.

Background:  Estimating influenza incidence in outpatient settings is challenging. We used outpatient healthcare practice populations as a proxy to estimate community incidence of influenza‐like illness (ILI) and laboratory‐confirmed influenza‐associated ILI.

Methods:  From October 2009 to July 2010, 38 outpatient practices in seven jurisdictions conducted surveillance for ILI (fever with cough or sore throat for patients ≥2 years; fever with ≥1 respiratory symptom for patients <2 years). From a sample of patients with ILI, respiratory specimens were tested for influenza.

Results:  During the week of peak influenza activity (October 24, 2009), 13% of outpatient visits were for ILI and influenza was detected in 72% of specimens. For the 10‐month surveillance period, ILI and influenza‐associated ILI incidence were 20·0 (95% CI: 19·7, 20·4) and 8·7/1000 (95% CI: 8·2, 9·2) persons, respectively. Influenza‐associated ILI incidence was highest among children aged 2–17 years. Observed trends were highly correlated with national ILI and virologic surveillance.

Conclusions:  This is the first multistate surveillance system demonstrating the feasibility of using outpatient practices to estimate the incidence of medically attended influenza at the community level. Surveillance demonstrated the substantial burden of pandemic influenza in outpatient settings and especially in children aged 2–17 years. Observed trends were consistent with established syndromic and virologic systems.

Diagnostic performance of the BinaxNow Influenza A&B rapid antigen test in ED patients

OBJECTIVE

The objective of this study is to evaluate the diagnostic performance of the BinaxNow Influenza A&B rapid antigen test (RAT) in emergency department (ED) patients.

METHODS

We prospectively enrolled a systematic sample of ED patients older than 6 months with acute respiratory symptoms or nonlocalizing fever during 3 consecutive influenza seasons (2008-2011). Nasal and throat swabs collected by research personnel were tested for influenza by real-time reverse transcription-polymerase chain reaction (RT-PCR). Clinicians independently ordered RATs during clinical care; these specimens were collected by clinical staff and tested for influenza using the BinaxNow RAT. Patients with both a research RT-PCR and clinical RAT were included in the study. Rapid antigen test diagnostic performance was evaluated using RT-PCR as a criterion standard, with preplanned, stratified analysis for subject age, duration of symptoms, influenza subtype, and polymerase chain reaction cycle threshold, which provides a semiquantitative estimate of viral load.

RESULTS

Of 561 subjects enrolled, 131 (23.4%) had a positive RT-PCR, and 37 (6.6%) had a positive RAT. Overall, RAT performance included sensitivity of 24.4% (95% confidence interval [CI], 17.5%-32.9%), specificity of 98.8% (95% CI, 97.1%-99.6%), positive predictive value of 86.5% (95% CI, 70.4%-94.9%), negative predictive value of 81.1% (95% CI, 77.4%-84.3%). Rapid antigen test sensitivities were low for all categories of subject age, symptom duration, influenza subtype, and cycle threshold.

CONCLUSION

The BinaxNow RAT demonstrated high specificity and poor sensitivity in ED patients selected by treating clinicians for influenza testing. A negative RAT is a poor predictor for the absence of influenza in the ED and should not be used as a criterion to withhold antiviral medications.

Real-time reverse transcriptase PCR assay for improved detection of human metapneumovirus

BACKGROUND

Human metapneumovirus (HMPV) is a paramyxovirus with multiple genetic lineages that is a leading cause of acute respiratory disease. Several RT-PCR assays have been described based on limited available sequence data.

OBJECTIVES

To develop a broadly reactive real-time RT-PCR assay for HMPV that allows for a rapid, sensitive, and specific detection in a clinical or research setting.

STUDY DESIGN

Three published assays for HMPV were modified based on analysis of multiple HMPV sequences obtained from GenBank. Original and modified assays were tested against prototype HMPV strains from each genetic sublineage, multiple isolates of HMPV from different years, a collection of clinical specimens, and commercial validation panels.

RESULTS

A number of potential sequence mismatches with diverse HMPV strains were identified. Modifications were made to oligonucleotides to improve annealing efficiency. Primers and probes based on newer sequence data offered enhanced detection of all subgroups, especially for low titer specimens. The new primers and probe detected multiple clinical isolates of HMPV collected over a twenty-year period. The modified assay improved detection of HMPV in a panel of clinical specimens, and correctly identified HMPV samples in two commercial validation sets.

CONCLUSIONS

We report a modified real-time RT-PCR assay for HMPV that detects all genetic lineages with high sensitivity.

Influenza vaccination for older adults

Influenza vaccines were developed in the 1930s and were shown in randomized clinical trials to prevent influenza in young healthy adults. The significant morbidity and mortality associated with influenza in adults, age 65 y and older, prompted the early recommendation for influenza vaccination in that age group, based on efficacy data in younger adults. Subsequently a number of studies have demonstrated vaccine effectiveness in older adults, but it appears to be lower than in younger adults. New vaccines are being developed with enhanced immunogenicity to improve the protection of older adults. In the meantime, the currently licensed influenza vaccines need to be administered annually to prevent the estimated 90,000 hospitalizations and 5,000 deaths attributed to influenza in adults ≥65 y of age each year.

Rethinking approaches to improve the utilization of nucleic acid amplification tests for detection and characterization of influenza A in diagnostic and reference laboratories

Influenza A virus (IFVA) is a significant cause of respiratory infections worldwide and was also responsible for a recent pandemic in 2009. Laboratory identification of IFVA can guide antiviral therapy, assist in cohorting of patients and prevent antibiotic use. Characterization of the virus can track the emergence of novel strains, identify resistance and determine how circulating strains match with vaccine components. The gold standard for detection and characterization of IFVA is nucleic acid amplification technology (e.g., reverse transcriptase PCR [RT-PCR]), which must contend with a constantly evolving viral genome. Although molecular technology has been available for over two decades, there is still an operational gap between assay design and utilization of these tests for the diagnosis and characterization of IFVA. This review will discuss issues surrounding the implementation and use of RT-PCR for the identification and characterization of IFVA, and speculate on why RT-PCR has not been used more widely in clinical laboratories or moved closer to the patient. Newer, less widely used technologies that may change our laboratory practices will be identified and the authors will close with an attempt to identify some future applications of RT-PCR-based technologies for the detection and characterization of IFVA.

Diagnostic tests for influenza infection

PURPOSE OF REVIEW

The 2009 H1N1 pandemic focused attention on the speed and accuracy of influenza diagnostic methods. This review provides an update on current tests and new developments.

RECENT FINDINGS

Widely used rapid antigen tests and immunofluorescence tests were generally less sensitive for 2009 H1N1 influenza than for seasonal influenza. In addition, marked variability was reported for the same tests in different settings and patient groups. The advantages of molecular testing gained wide recognition, namely high sensitivity, speed compared with culture, ability to assess viral load and to identify subtype. Although adoption of influenza molecular testing can be expected to accelerate, immunoassays and rapid cultures performed on site retain advantages for many facilities. Falsely negative results were seen with all methods, especially for samples collected very early or late.

SUMMARY

Influenza diagnostic test performance can be adversely affected by viral genetic and antigenic changes and should be re-assessed annually. Variability in sensitivity and specificity of the same test in different settings highlights the need for each laboratory to ensure optimal procedures and work with clinicians to improve sample quality. Manufacturers have been motivated to improve immunoassays and develop simpler and faster multiplex molecular tests, hopefully in advance of the next pandemic.

Host and viral factors associated with severity of human rhinovirus-associated infant respiratory tract illness

BACKGROUND

Risk factors for severe human rhinovirus (HRV)-associated infant illness are unknown.

OBJECTIVES

We sought to examine the role of HRV infection in infant respiratory tract illness and assess viral and host risk factors for HRV-associated disease severity.

METHODS

We used a prospective cohort of term, previously healthy infants enrolled during an inpatient or outpatient visit for acute upper or lower respiratory tract illness during the fall-spring months of 2004-2008. Illness severity was determined by using an ordinal bronchiolitis severity score, with higher scores indicating more severe disease. HRV was identified by means of real-time RT-PCR. The VP4/VP2 region from HRV-positive specimens was sequenced to determine species.

RESULTS

Of 630 infants with bronchiolitis or upper respiratory tract illnesses (URIs), 162 (26%) had HRV infection; HRV infection was associated with 18% of cases of bronchiolitis and 47% of cases of URI. Among infants with HRV infection, 104 (64%) had HRV infection alone. Host factors associated with more severe HRV-associated illness included a maternal and family history of atopy (median score of 3.5 [interquartile range [IQR], 1.0-7.8] vs 2.0 [IQR, 1.0-5.2] and 3.5 [IQR, 1.0-7.5] vs 2.0 [IQR, 0-4.0]). In adjusted analyses maternal history of atopy conferred an increase in the risk for more severe HRV-associated bronchiolitis (odds ratio, 2.39; 95% CI, 1.14-4.99; P = .02). In a similar model maternal asthma was also associated with greater HRV-associated bronchiolitis severity (odds ratio, 2.49, 95% CI, 1.10-5.67; P = .03). Among patients with HRV infection, 35% had HRVA, 6% had HRVB, and 30% had HRVC.

CONCLUSION

HRV infection was a frequent cause of bronchiolitis and URIs among previously healthy term infants requiring hospitalization or unscheduled outpatient visits. Substantial viral genetic diversity was seen among the patients with HRV infection, and predominant groups varied by season and year. Host factors, including maternal atopy, were associated with more severe infant HRV-associated illness.

Effectiveness of seasonal vaccine in preventing confirmed influenza-associated hospitalizations in community dwelling older adults

BACKGROUND

Current evidence supporting the effectiveness of influenza vaccine in preventing hospitalizations in older adults is insufficient.

METHODS

During 3 influenza seasons, 2006-2009, community-dwelling adults aged ≥50 y hospitalized with respiratory symptoms were prospectively enrolled in this study. We tested nose and throat samples for influenza virus by reverse transcriptase-polymerase chain reaction. We estimated vaccine effectiveness by comparing vaccination status between influenza-positive cases and influenza-negative controls using logistic regression models with propensity score adjustment.

RESULTS

Overall, 450 (59%) of 763 eligible patients were enrolled; 417 (93%) of enrolled patients had adequate respiratory samples, had known influenza vaccination status, and were community-dwelling. The proportions of influenza-positive patients were 8%, 20%, and 6% in the 3 successive seasons. Of 39 influenza-positive participants, 14 (36%) were vaccinated compared with 250 (66%) of 378 influenza-negative controls. Propensity score-adjusted vaccine effectiveness for the 3 seasons combined was 61.2% (95% confidence interval, 17.5%-81.8%).

CONCLUSION

Overall, in this moderately well-vaccinated population of older adults, laboratory-confirmed influenza virus accounted for 9.3% (95% confidence interval, 6.6%-12.1%) of all respiratory hospitalizations during 3 influenza seasons, and influenza vaccination prevented 61.2% of such hospitalizations.