An algorithm to diagnose influenza infection: evaluating the clinical importance and impact on hospital costs of screening with rapid antigen detection tests

A narrative review of nine commercial point of care influenza tests: an overview of methods, benefits, and drawbacks to rapid influenza diagnostic testing

CONTEXT

Rapid influenza diagnostic tests (RIDTs) are becoming increasingly accurate, available, and reliable as the first line of testing when suspecting influenza infections, although the global burden of influenza infections remains high. Rapid diagnosis of influenza infections has been shown to reduce improper or delayed treatment and to increase access to diagnostic measures in public health, primary care, and hospital-based settings.

OBJECTIVES

As the use of RIDTs continues to expand in all healthcare settings, there is a multitude of molecular techniques being employed by these various testing platforms. With this in mind, we compare the sensitivity, specificity, and time to diagnosis for nine highly utilized commercial RIDTs.

METHODS

Nine commercially available RIDTs were identified from the US Centers for Disease Control and Prevention (CDC) website, which were also referenced on PubMed by name within the title or abstract of peer-reviewed publications examining the sensitivity and specificity of each test against a minimum of three influenza A virus (IAV) strains as well as seasonal influenza B virus (IBV). Data from the peer-reviewed publications and manufacturers' websites were combined to discuss the sensitivity, specify, and time to diagnosis associated with each RIDT.

RESULTS

The sensitivity and specificity across the examined RIDTs were greater than 85.0% for both IAV and IBV across all platforms, with the reverse transcriptase-polymerase chain reaction (RT-PCR) assays maintaining sensitivity and specificity greater than 95.0% for all viruses tested. However, the RT-PCR platforms were the longest in time to diagnosis when compared to the other molecular methods utilized in the examined RIDTs.

CONCLUSIONS

Herein, we discussed the benefits and limitations of nine commercially available RIDTs and the molecular techniques upon which they are based, showing the relative accuracy and speed of each test for IAV and IBV detection as reported by the peer-reviewed literature and commercial manufacturers.

Comparing the cobas Influenza A/B Nucleic acid test for use on the cobas Liat System (Liat) with rapid antigen tests for clinical management of Japanese patients at the point of care

Background

Rapid diagnosis of influenza is critical in preventing the spread of infection and ensuring patients quickly receive antiviral medication to reduce the severity and duration of influenza symptoms, whilst controlling the spread of the causative virus. In Japan patients are often administered anti-influenza medication following a positive rapid antigen detection test (RADT) result. However, the sensitivity of RADTs can lead to false negative results. The cobas^® Influenza A/B Nucleic acid test for use on the cobas Liat^® System (Liat) is a molecular point-of-care method that can provide a more sensitive alternative to RADTs for rapid influenza diagnosis and treatment.

Methods

In this prospective multicenter study, diagnostic performance of the Liat test was compared with RADTs in patients presenting with influenza-like-illness. Test performance was also assessed by time since symptom onset.

Results

Of 419 patients enrolled, 413 were evaluable for all designated tests. Most patients had type-A infection, and only one patient had influenza type B. In 413 patients, the sensitivity and specificity (95% CI) of the Liat test were 99.5% (97.2–99.9%) and 99.5% (97.4–99.9%), respectively, and were 79.7% (73.5–84.7%) and 95.4% (91.7–97.5%) for RADTs. For patients tested <12 hours from symptom onset, the Liat test had significantly higher sensitivity than RADTs (p<0.0001).

Conclusion

Overall, compared with standard of care RADTs, the Liat test was more sensitive and specific in children and adults, particularly in the early stages of infection. Greater sensitivity can enable earlier diagnosis and may better inform appropriate antiviral treatment decisions.

Use of Saliva Swab for Detection of Influenza Virus in Patients Admitted to an Emergency Department

Nasopharyngeal (NP) specimens are commonly used for the detection of influenza, but saliva swabs are easier to obtain and cause less discomfort to the patients. The objective of this study was to evaluate the usefulness of saliva swab specimens for the diagnosis of influenza compared with NP specimens. Influenza virus detection rate in saliva and NP swabs was compared in adult patients admitted to an emergency department from January to March 2020, using the Xpert Xpress Flu/respiratory syncytial virus (RSV) test. Cycle threshold (C_T) values were evaluated in all the cases. Among the 82 patients recruited, 19 had an influenza-positive diagnostic test result (11 influenza A and 8 influenza B). Overall, the agreement between saliva and NP swabs results was 97.6% (80/82; κ = 0.929; 95% confidence interval [CI], 0.832 to 1.0). There was no significant difference in the influenza detection rate between saliva swab and NP specimens (20.7% [17/82] versus 23.2% [19/82]; P = 0.5). There were only two discordant results (influenza B in an NP and false negative in a saliva sample). Manual inspection of the amplification curves showed that influenza RNA had been amplified in saliva with high C_Ts (C_T of 40) that the test reported as a negative result. The overall sensitivity and specificity for saliva was 89.5% (73.0% to 100%) and 100% (99.2% to 100%), respectively. In all the cases, the same influenza virus (A/B) was detected. Median C_T values were significantly lower in NP (31; interquartile range [IQR], 21.0 to 32.0) than in saliva (33; IQR, 23.0 to 38.0) (P = 0.001) specimens. Saliva swabs have high sensitivity and specificity for the detection of influenza virus by the Xpert Xpress Flu/RSV test and a high overall agreement and C_T correlation with NP specimens. Saliva swab is a feasible specimen type for influenza testing that might be easily self-collected with minimal equipment and discomfort.

IMPORTANCE Early detection of influenza virus is important for guiding antiviral and antibacterial treatment for infection control and public health measures. We have observed that saliva swab specimens have high sensitivity and specificity for the detection of influenza by the Xpert Xpress Flu/respiratory syncytial virus (RSV) test and high overall agreement and C_T correlation with nasopharyngeal specimens. Saliva swab may therefore be a feasible specimen type for influenza testing that can be easily self-collected with minimal equipment and discomfort.

Evaluation of Lateral-Flow Assay for Rapid Detection of Influenza Virus

Background

Influenza virus mainly causes acute respiratory infections in humans. However, the diagnosis of influenza is not accurate based on clinical evidence, as the symptoms of flu are similar to other respiratory virus. The lateral-flow assay is a rapid method to detect influenza virus. But the effectiveness of the technique in detecting flu viruses is unclear. Hence, a meta-analysis would be performed to evaluate the accuracy of LFA in detecting influenza virus.

Methods

Relevant literature was searched out in PubMed, Embase, Web of Science, and Cochrane Library databases with the keywords "lateral flow assay" and "flu virus". By Meta-DiSc software, pooled sensitivity, pooled specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), summary receiver operating characteristic curve (SROC), and area under the curve (AUC) can be calculated.

Results

This meta-analysis contains 13 studies and 24 data. The pooled sensitivity and specificity of the influenza virus detected by LFA were 0.84 (95% CI: 0.82-0.86) and 0.97 (95% CI: 0.97-0.98), respectively. The pooled values of PLR, NLR, DOR, and SROC were 32.68 (17.16-62.24), 0.17 (0.13-0.24), 334.07 (144.27-773.53), and 0.9877. No publication bias was found.

Conclusions

LFA exhibited high sensitivity and specificity in diagnosing influenza virus. It is a valuable alternative method which can diagnose influenza virus quickly. However, more evidence is required to confirm whether LFA is comparable to traditional methods for detecting the virus.

Magnetic Particle Spectroscopy for Detection of Influenza A Virus Subtype H1N1

Magnetic nanoparticles (MNPs) with proper surface functionalization have been extensively applied as labels for magnetic immunoassays, carriers for controlled drug/gene delivery, tracers and contrasts for magnetic imaging, etc. Here, we introduce a new biosensing scheme based on magnetic particle spectroscopy (MPS) and the self-assembly of MNPs to quantitatively detect H1N1 nucleoprotein molecules. MPS monitors the harmonics of oscillating MNPs as a metric for the freedom of rotational process, thus indicating the bound states of MNPs. These harmonics can be readily collected from nanogram quantities of iron oxide nanoparticles within 10 s. The H1N1 nucleoprotein molecule hosts multiple different epitopes that forms binding sites for many IgG polyclonal antibodies. Anchoring IgG polyclonal antibodies onto MNPs triggers the cross-linking between MNPs and H1N1 nucleoprotein molecules, thereby forming MNP self-assemblies. Using MPS and the self-assembly of MNPs, we were able to detect as low as 44 nM (4.4 pmole) H1N1 nucleoprotein. In addition, the morphologies and the hydrodynamic sizes of the MNP self-assemblies are characterized to verify the MPS results. Different MNP self-assembly models such as classical cluster, open ring tetramer, and chain model as well as multimers (from dimer to pentamer) are proposed in this paper. Herein, we claim the feasibility of using MPS and the self-assembly of MNPs as a new biosensing scheme for detecting ultralow concentrations of target biomolecules, which can be employed as rapid, sensitive, and wash-free magnetic immunoassays.

Prognostic Implications of Influenza Virus Infection in a Cardiac Intensive Care Unit: Potential Impact of a Screening Program

Objectives: Our goal was to determine the presentation and prognosis of influenza in an intensive cardiac care unit and to analyze the impact of an active surveillance program in the diagnosis. Methods: We performed a prospective registry during the flu season in a coronary unit. In the first phase, no systematic screening was performed. Systematic influenza A and B detection was performed in a second phase for all patients admitted. Results: From 227 patients, we identified 17 (7.5%) with influenza. Influenza patients were more likely to have a non-ischemic cause of admission (14 patients [82.4%] vs. 48 patients [40.3%], p = 0.002), fever (8 patients [47.1%] vs. 3 patients [2.6%], p < 0.001), and respiratory failure (7 patients [41.2%] vs. 8 patients [7%], p = 0.001). Influenza infection was an independent predictor of mortality (odds ratio 12.0, 95% confidence interval 1.9–13.6, p < 0.001). The incidence of influenza was 6.6% (6 patients) when no active screening was performed and 7.9% (11 patients) when systematic detection was performed (p = 0.005). The time to diagnosis was shorter in the systematic screening phase (0.92 ± 1.6 vs. 5.2 ± 3.8 days, p = 0.01). Conclusions: Influenza affects approximately 8% of patients admitted to an intensive cardiac care unit during the flu season, with a high mortality rate. An active surveillance program improves early detection.

Principles and Practice of Antibiotic Stewardship in the ICU

In the face of emerging drug-resistant pathogens and a decrease in the development of new antimicrobial agents, antibiotic stewardship should be practiced in all critical care units. Antibiotic stewardship should be a core competency of all critical care practitioners in conjunction with a formal antibiotic stewardship program (ASP). Prospective audit and feedback, and antibiotic time-outs, are effective components of an ASP in the ICU. As rapid diagnostics are introduced in the ICU, assessment of performance and effect on outcomes will clearly be needed. Disease-specific stewardship for community-acquired pneumonia that relies on clinical pathways may be particularly high-yield. Computerized decision support has the potential to individualize stewardship for specific patients. Finally, infection control and prevention is the cornerstone of every ASP.

Detection Methods of Human and Animal Influenza Virus-Current Trends

The basic affairs connected to the influenza virus were reviewed in the article, highlighting the newest trends in its diagnostic methods. Awareness of the threat of influenza arises from its ability to spread and cause a pandemic. The undiagnosed and untreated viral infection can have a fatal effect on humans. Thus, the early detection seems pivotal for an accurate treatment, when vaccines and other contemporary prevention methods are not faultless. Public health is being attacked with influenza containing new genes from a genetic assortment between animals and humankind. Unfortunately, the population does not have immunity for mutant genes and is attacked in every viral outbreak season. For these reasons, fast and accurate devices are in high demand. As currently used methods like Rapid Influenza Diagnostic Tests lack specificity, time and cost-savings, new methods are being developed. In the article, various novel detection methods, such as electrical and optical were compared. Different viral elements used as detection targets and analysis parameters, such as sensitivity and specificity, were presented and discussed.

Role of the Clinical Microbiology Laboratory in Antimicrobial Stewardship

For adequate antimicrobial stewardship, microbiology needs to move from the laboratory to become physically and verbally amenable to the caregivers of an institution. Herein, we describe the contributions of our microbiology department to the antimicrobial stewardship program of a large teaching hospital as 10 main points ranging from the selection of patients deemed likely to benefit from a fast track approach, to their clinical samples, or the rapid reporting of results via a microbiology hotline, to rapid searches for pathogens and susceptibility testing. These points should serve as guidelines for similar programs designed to decrease the unnecessary use of antimicrobials.

Systematic review of the impact of point-of-care testing for influenza on the outcomes of patients with acute respiratory tract infection

Acute respiratory tract infections are a major cause of morbidity and mortality and represent a significant burden on the health care system. Laboratory testing is required to definitively distinguish infecting influenza virus from other pathogens, resulting in prolonged emergency department (ED) visits and unnecessary antibiotic use. Recently available rapid point-of-care tests (POCT) may allow for appropriate use of antiviral and antibiotic treatments and decrease patient lengths of stay. We undertook a systematic review to assess the effect of POCT for influenza on three outcomes: (1) antiviral prescription, (2) antibiotic prescription, and (3) patient length of stay in the ED. The databases Medline and Embase were searched using MeSH terms and keywords for influenza, POCT, antivirals, antibiotics, and length of stay. Amongst 245 studies screened, 30 were included. The majority of papers reporting on antiviral prescription found that a positive POCT result significantly increased use of antivirals for influenza compared with negative POCT results and standard supportive care. A positive POCT result also led to decreased antibiotic use. The results of studies assessing the effect of POCT on ED length of stay were not definitive. The studies assessed in this systematic review support the use of POCT for diagnosis of influenza in patients suffering an acute respiratory infection. Diagnosis using POCT may lead to more appropriate prescription of treatments for infectious agents. Further studies are needed to assess the effect of POCT on the length of stay in ED.

Evaluation of a two-stage testing algorithm for the diagnosis of respiratory viral infections

New on-demand multiplex molecular respiratory viral diagnostics offer superior performance although can be expensive and some platforms cannot process multiple specimens simultaneously. We performed a retrospective study reviewing results of patients tested for respiratory viruses following introduction of a two-stage testing algorithm incorporating an initial screen with Sofia® immunoassay then secondary Biofire Filmarray®, and compared to a period when only Filmarray® was used. Of 2976 testing episodes, 1814 underwent initial Sofia® then follow-up FilmArray®. A diagnosis of influenza was made by Sofia® in 282 patients, and by FilmArray® in an additional 163 (median time to result 1.12 hours versus 3.46 hours, P < 0.001). Significantly more patients received their diagnosis within 90 minutes in winter despite testing more samples (11.1% versus 3.4%, P < 0.001), and approximately $36,000 was saved. An algorithmic approach to respiratory viral diagnosis can combine the advantages of accuracy and speed and be cost saving.

Prospective comparative study of characteristics associated with influenza A and B in adults

OBJECTIVES

To describe and compare the epidemiological characteristics associated with influenza type A and B as well as the characteristics associated with influenza pneumonia. The secondary objective was to evaluate the performance of influenza rapid diagnostic tests (RDT) in the emergency department.

PATIENTS AND METHODS

Prospective study, including 251 adult patients admitted to the emergency department during the 2013-2014 influenza outbreaks for flu-like illness confirmed by RT-PCR.

RESULTS

A total of 106 patients were infected with influenza type B (42%) and 145 with influenza type A (58%). Mean age was 56 and the sex-ratio was 0.9. In a multivariate analysis, the only factor independently related with the type of influenza strain was the patient's age. Overall, 17% of influenza-infected patients were vaccinated and 38% presented with pneumonia, with no significant difference between strains. In a univariate analysis, the risk factors associated with the occurrence of pneumonia were age, vaccination, and chronic obstructive pulmonary disease. Only 22% of samples positive by RT-PCR for influenza B and 40% for influenza A were positive by RDT.

CONCLUSION

Influenza type A and type B had similar clinical and biological signs, including severity. Influenza type B should not be neglected. Any emergency department may use the RDT for its ease-of-use and rapidity. However, its low sensitivity should be taken into consideration when interpreting results.

The impact of commercial rapid respiratory virus diagnostic tests on patient outcomes and health system utilization

INTRODUCTION

Acute respiratory tract infections due to influenza A/B and respiratory syncytial virus (RSV) are major causes of morbidity and mortality globally. Rapid tests for detection of these pathogens include antigen detection point of care tests (POC) and newer easy to use molecular tests. From experience, these assays improve both laboratory workflow and assay interpretation issues. However, the question of the benefits of using rapid test technology compared to routine laboratory testing for respiratory viral pathogens is still often asked. Areas covered: Specifically, this review aims to; 1) identify clinical/patient indicators that can be measured prior to and following the implementation of rapid diagnostic test for influenza and RSV, 2) provide multiple perspectives on the extent of impact of a rapid diagnostic test, including direct and indirect outcomes, and 3) identify the technological advancements in the development of rapid testing, demonstrating a timeline that transitions from antigen-based assays to molecular assays. Expert commentary: Key benefits to the use of either antigen-based or molecular rapid tests for patient care, patient flow within institutions, as well as laboratory utilization are identified. Due to improved test characteristics, the authors feel that rapid molecular tests have greater benefits than antigen-based detection methods.

Influenza A and B co-infection: a case-control study and review of the literature

Influenza virus infection remains a major cause of morbidity and mortality during winter seasons. Bacterial and virus co-infection is a commonly described situation in these patients. However, data on co-infection by influenza A and B viruses are lacking. In this study, we present the cases of co-infection by influenza A and B viruses during the winter season of 2014-2015 in our institution. We analyzed 2759 samples from 2111 patients and found that 625 samples corresponding to 609 patients were positive for influenza A or B virus. A total of 371 patients had influenza A, 228 had influenza B, and 10 (1.6 %) had influenza A and B virus detection in the same sample. The median age of co-infected patients was 78.6 years, and only one of the co-infected patients died because of the infection. Comparison with a control group of mono-infected patients revealed that co-infection was significantly associated with nosocomial acquisition [odds ratio (OR) = 4.5, 95 % confidence interval (CI) = 1.05-19.25, p = 0.042]. However, co-infection was not associated with worse outcome, previous underlying condition, or vaccination status. Multivariate analysis revealed that co-infection was not an independent risk factor for death and that no single risk factor could predict co-infection.