Comparison of a new lateral-flow chromatographic membrane immunoassay to viral culture for rapid detection and differentiation of influenza A and B viruses in respiratory specimens

New technologies and reagents in lateral flow assay (LFA) designs for enhancing accuracy and sensitivity

Lateral flow assays (LFAs) are a popular method for quick and affordable diagnostic testing because they are easy to use, portable, and user-friendly. However, LFA design has always faced challenges regarding sensitivity, accuracy, and complexity of the operation. By integrating new technologies and reagents, the sensitivity and accuracy of LFAs can be improved while minimizing the complexity and potential for false positives. Surface enhanced Raman spectroscopy (SERS), photoacoustic techniques, fluorescence resonance energy transfer (FRET), and the integration of smartphones and thermal readers can improve LFA accuracy and sensitivity. To ensure reliable and accurate results, careful assay design and validation, appropriate controls, and optimization of assay conditions are necessary. Continued innovation in LFA technology is crucial to improving the reliability and accuracy of rapid diagnostic testing and expanding its applications to various areas, such as food testing, water quality monitoring, and environmental testing.

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.

Immunosensor-based label-free and multiplex detection of influenza viruses: State of the art

The ability of influenza viruses to rapidly evolve has caused significant challenges in viral surveillance, diagnosis, and therapeutic development. Molecular sequencing methods, though powerful tools for monitoring influenza evolution at the genetic level, are not able to fully characterize the antigenic properties of influenza viruses. Understanding influenza virus antigenicity is critical to vaccine development and disease prevention. Traditional immunoassays which have been widely used for evaluating influenza antigenicity have limited throughput. To alleviate these problems, new bioanalytical tools to investigate influenza antigenicity by measuring antibody-antigen binding are an active area of research. Herein, we review immunosensor technologies from the aspects of various sensing principles, while highlighting recent developments in multiplex, label-free detection strategies. Highlighted technologies include electrochemical immunosensors relying on impedimetric detection; these demonstrate simple design and cost effectiveness for mass production. Antibody arrays implemented on an optical interferometric sensor system allow systematic characterization of influenza antigenicity. Quartz microbalance immunosensors are highly sensitive but have yet to be explored for multiplex sensing. Immunosensors made on lateral flow strips have shown promise in rapid diagnosis of influenza subtypes. We anticipate that these and other technologies discussed in the review will facilitate advances in the study of influenza, and other viral pathogens.

A new point-of-care test for the diagnosis of infectious diseases based on multiplex lateral flow immunoassays

Infectious diseases are transmissible or communicable illnesses and can spread quickly in some areas and become epidemics. It is critical to quickly diagnose initial infections and prevent further spread through in vitro diagnosis. However, current detection strategies have exhibited a lack of balance with regard to accuracy, time consumption, and portability until recently (e.g. serology, culturing, molecular tests, etc.). Alternatively, many studies have focused on point-of-care testing (POCT), which combines simple, rapid, and exact on-site diagnostic platforms. Moreover, multiplex detectability is necessary for emergency treatment depending on the stage of the disease or interactional infections. The lateral flow assay (LFA) is the most popular diagnostic tool that meets the required standards for colorimetric assays. Here, we review lateral flow assays based on the immune reactions for the simultaneous diagnosis of infectious diseases as the POC test. The assays employed various forms and approaches in terms of the multiplexing level system for improving the sensitivity and specificity. We briefly describe the state-of-the-art infection diagnostic methods and published performances that have been classified into three categories based on the application forms of the lateral flow immunoassay. Also, we discuss further uses of LFA and other technologies for more effective infectious disease POCT.

Liposome-Enhanced Lateral-Flow Assays for Clinical Analyses

Clinical and environmental analyses frequently necessitate rapid, simple, and inexpensive point-of-care or field tests. These semiquantitative tests may be later followed up by confirmatory laboratory-based assays, but provide an initial scenario assessment important for resource mobilization and threat confinement. Lateral-flow assays (LFAs) and dip-stick assays, which are typically antibody-based and yield a visually detectable signal, provide an assay format suiting these applications extremely well. Signal generation is commonly obtained through the use of colloidal gold or latex beads, which yield a colored band either directly proportional or inversely proportional to the concentration of the analyte of interest. Here, dye-encapsulating liposomes as a highly visible alternative are discussed. The semiquantitative LFA biosensor described in this chapter relies on a sandwich immunoassay for the detection of myoglobin in whole blood. After an acute myocardial infarction (AMI) event, several cardiac markers are released into the blood, the most common of which are troponin, creatine kinase MB, C-reactive protein, and myoglobin. Due to its early release, myoglobin has value as an indicator of a recent heart attack amongst conditions which present with similar symptoms and its lack of elevation can effectively rule out a heart attack (Brogan et al., Ann Emerg Med 24:665-671, 1994). The assay described within relies on sandwich complex formation between a membrane immobilized capture monoclonal antibody against myoglobin, a detector biotinylated monoclonal antibody against a different epitope on myoglobin, and streptavidin-conjugated visible dye (sulforhodamine B)-encapsulating liposomes to allow for signal generation.

Using an aqueous two-phase polymer-salt system to rapidly concentrate viruses for improving the detection limit of the lateral-flow immunoassay

The development of point-of-need (PON) diagnostics for viruses has the potential to prevent pandemics and protects against biological warfare threats. Here we discuss the approach of using aqueous two-phase systems (ATPSs) to concentrate biomolecules prior to the lateral-flow immunoassay (LFA) for improved viral detection. In this paper, we developed a rapid PON detection assay as an extension to our previous proof-of-concept studies which used a micellar ATPS. We present our investigation of a more rapid polymer-salt ATPS that can drastically improve the assay time, and show that the phase containing the concentrated biomolecule can be extracted prior to macroscopic phase separation equilibrium without affecting the measured biomolecule concentration in that phase. We could therefore significantly decrease the time of the diagnostic assay with an early extraction time of just 30 min. Using this rapid ATPS, the model virus bacteriophage M13 was concentrated between approximately 2 and 10-fold by altering the volume ratio between the two phases. As the extracted virus-rich phase contained a high salt concentration which destabilized the colloidal gold indicator used in LFA, we decorated the gold nanoprobes with polyethylene glycol (PEG) to provide steric stabilization, and used these nanoprobes to demonstrate a 10-fold improvement in the LFA detection limit. Lastly, a MATLAB script was used to quantify the LFA results with and without the pre-concentration step. This approach of combining a rapid ATPS with LFA has great potential for PON applications, especially as greater concentration-fold improvements can be achieved by further varying the volume ratio. Biotechnol. Bioeng. 2014;111: 2499-2507. © 2014 Wiley Periodicals, Inc.

A packaged paper fluidic-based microdevice for detecting gene expression of influenza A virus

Pathotyping and subtyping of influenza A virus were performed with a packaged paper fluidic-based analytical microdevice (PFAM) after one-step reverse transcription-polymerase chain reaction (RT-PCR). The PFAM contains two test lines: one for detecting M gene to identify the influenza A virus and another for haemagglutinin subtyping to determine the viral strain among H1N1, H3N2, and H5N1. The M gene and the haemagglutinin gene (H1, H3, and H5 genes) were amplified by using the Digoxigenin and the Texas Red modified primers, respectively, in the multiplex RT-PCR. The amplicon products were loaded in the conjugate pad of the PFAM in which the streptavidin coated gold nanoparticles were linked with the biotin moieties that were incorporated in the middle of the DNA strands, and then captured by the anti-Digoxigenin and anti-Texas Red immobilized on the test lines. Influenza A H1N1, H3N2, and H5N1 could be identified with a limit of detection of 10(2) copies of RNA templates in 10 min. Pathotyping and subtyping of the clinical nasopharyngeal swab samples were also analyzed whose results were confirmed by real-time RT-PCR.

Point-of-Care Testing for Pandemic Influenza and Biothreats

New and reemerging infectious diseases, such as pandemic viruses and resistant bacteria, pose a serious threat in the 21st century. Some of these agents represent global security threats. This review provides an overview of diagnostic challenges presented by pandemic influenza and biothreat agents. The article summarizes recent pandemics and disease outbreaks, point-of-care influenza diagnostic tests, biothreat agents, biothreat instrument systems, and technologies in development. It highlights how medical innovation and health care initiatives can help prepare health care professionals and public health personnel to handle future crises. Based on gap analysis for current point-of-care testing deficiencies, it concludes with policy recommendations that will enhance preparedness. (Disaster Med Public Health Preparedness. 2009;3(Suppl 2):S193–S202)

Simultaneous detection of high-sensitivity cardiac troponin I and myoglobin by modified sandwich lateral flow immunoassay: proof of principle

BACKGROUND

Although numerous lateral flow immunoassays (LFIAs) have been developed and widely used, inadequate analytical sensitivity and the lack of multiple protein detection applications have limited their clinical utility. We developed a new LFIA device for the simultaneous detection of high-sensitivity cardiac troponin I (hs-cTnI) and myoglobin (Myo).

METHODS

We used a gold nanoparticle (AuNP) doubly labeled complex, in which biotinylated single-stranded DNA was used as a linkage to integrate 2 AuNPs and streptavidin-labeled AuNP, as an amplifier to magnify extremely low signals.

RESULTS

The detection limit of 1 ng/L achieved for hs-cTnI was 1000 times lower than that obtained in a conventional LFIA. The detection limit for simultaneously measured Myo was 1 μg/L. The linear measurement ranges for hs-cTnI and Myo were 1-10 000 ng/L and 1-10 000 μg/L, respectively. We observed concordant results between the LFIA and clinical assays in sera from 12 patients with acute myocardial infarction (hs-cTnI r = 0.96; Myo r = 0.98). Assay imprecision was <11% for both hs-TnI and myo.

CONCLUSIONS

The described proof-of-principle LFIA method could be used as a point-of-care device in multiple protein quantification and semiquantitative analysis.

Enhancing the lateral-flow immunoassay for viral detection using an aqueous two-phase micellar system

Availability of a rapid, accurate, and reliable point-of-care (POC) device for detection of infectious agents and pandemic pathogens, such as swine-origin influenza A (H1N1) virus, is crucial for effective patient management and outbreak prevention. Due to its ease of use, rapid processing, and minimal power and laboratory equipment requirements, the lateral-flow (immuno)assay (LFA) has gained much attention in recent years as a possible solution. However, since the sensitivity of LFA has been shown to be inferior to that of the gold standards of pathogen detection, namely cell culture and real-time PCR, LFA remains an ineffective POC assay for preventing pandemic outbreaks. A practical solution for increasing the sensitivity of LFA is to concentrate the target agent in a solution prior to the detection step. In this study, an aqueous two-phase micellar system comprised of the nonionic surfactant Triton X-114 was investigated for concentrating a model virus, namely bacteriophage M13 (M13), prior to LFA. The volume ratio of the two coexisting micellar phases was manipulated to concentrate M13 in the top, micelle-poor phase. The concentration step effectively improved the M13 detection limit of the assay by tenfold from 5 × 10(8) plaque forming units (pfu)/mL to 5 × 10(7) pfu/mL. In the future, the volume ratio can be further manipulated to yield a greater concentration of a target virus and further decrease the detection limits of the LFA.

Evaluation of twenty rapid antigen tests for the detection of human influenza A H5N1, H3N2, H1N1, and B viruses

Twenty rapid antigen assays were compared for their ability to detect influenza using dilutions of virus culture supernatants from human isolates of influenza A H5N1 (clade 1 and 2 strains), H3N2 and H1N1 viruses, and influenza B. There was variation amongst the rapid antigen assays in their ability to detect different influenza viruses. Six of the 12 assays labeled as distinguishing between influenza A and B had comparable analytical sensitivities for detecting both influenza A H5N1 strains, although their ability to detect influenza A H3N2 and H1N1 strains varied. The two assays claiming H5 specificity did not detect either influenza A H5N1 strains, and the two avian influenza-specific assays detected influenza A H5N1, but missed some influenza A H3N2 virus supernatants. Clinical trials of rapid antigen tests for influenza A H5N1 are limited. For use in a pandemic where novel influenza strains are circulating (such as the current novel influenza A H1N1 09 virus), rapid antigen tests should ideally have comparable sensitivity and specificity for the new strains as for co-circulating seasonal influenza strains.

Liposome-enhanced lateral-flow assays for the sandwich-hybridization detection of RNA

Clinical and environmental analyses frequently necessitate rapid, simple, and inexpensive point-of-care or field tests. These semiquantitative tests may be later followed up by confirmatory laboratory-based assays, but can provide an initial scenario assessment important for resource mobilization and threat confinement. Lateral-flow assays (LFAs) and dip-stick assays, which are typically antibody-based and yield a visually detectable signal, provide an assay format suiting these applications extremely well. Signal generation is commonly obtained through the use of colloidal gold or latex beads, which yield a colored band either directly proportional or inversely proportional to the concentration of the analyte of interest. Here, dye-encapsulating liposomes as an alternative are discussed. The LFA biosensors described in this chapter rely on the sandwich-hybridization of a nucleic acid sequence-based amplified (NASBA) mRNA target between a membrane immobilized capture probe and a visible dye (sulforhodamine B)-encapsulating liposome conjugated reporter probe. Although the methodology of this chapter is focused on LFAs for the detection of RNA through sandwich hybridization, the information within can be readily adapted for sandwich and competitive immunoassays. Included are an introduction and application notes toward this end. These include notes ranging from the detection of nonamplified RNA and single-stranded DNA, conjugation protocols for antibodies and other proteins to liposomes, and universal assay formats.

Rapid assays for the diagnosis of influenza A and B viruses in patients evaluated at a large tertiary care children's hospital during two consecutive winter seasons

BACKGROUND

The rapid and accurate diagnosis of influenza facilitates antiviral therapy, judicious antibiotic usage, and cohorting patients to decrease nosocomial infection.

OBJECTIVE

To determine the utility of rapid influenza tests in a children's hospital.

STUDY DESIGN

Two in vitro rapid immunochromatographic assays that detect and distinguish influenza A and B viruses were compared to the reference standard of viral culture.

RESULTS

In 9186 patients tested, overall sensitivity of the rapid assays for influenza A was 64.4% and specificity was 98.3%. Sensitivity and specificity were 28% and 99.9%, respectively, for influenza B. Overall sensitivity and specificity for Remel Xpect (2004/2005) were 47.7% and 98.7% for influenza A, and 20.3% and 99.8% for influenza B, respectively. Overall sensitivity and specificity of Binax NOW Flu A&B (2005/2006) were 78.3% and 98% for influenza A, and 35.9% and 99.9% for influenza B, respectively. The results for influenza B with both assays were significantly lower than previously reported and lower than stated in the manufacturer's package insert.

CONCLUSIONS

In a contemporary clinical setting, rapid assays for influenza displayed significantly lower sensitivities, especially for influenza B, than prior reports. Differences in pre- and post-licensure performance demonstrate the importance of continuous evaluation of rapid diagnostic tests for influenza.

Development of a lateral flow assay for rapid detection of bovine antibody to Anaplasma marginale

A rapid lateral flow assay for detection of bovine antibody to Anaplasma marginale was developed. The assay used a recombinant peptide of major surface protein 5 as the antigen and a monoclonal antibody specific for bovine IgG(1) conjugated with colloidal gold beads for detection. Serum and anticoagulated blood samples were obtained from cattle in an area where anaplasmosis was endemic. The samples were selected based on positive identification of the organism in blood smears. The unclotted blood samples were used for PCR determination of the presence of A. marginale while the sera were tested by a commercial competitive enzyme immunoassay (CELISA) and by the lateral flow assay (LFA). Similar samples, collected at a Canadian sales barn, were tested by the CELISA and LFA and 10% were tested by PCR for the presence of A. marginale nucleic acid. In addition, stored serum samples from a second endemic area were tested by CELISA and LFA. Of the 114 smear positive samples, all were positive by CELISA and LFA. All samples were also positive by PCR. Samples from Canadian sources (n=524) were negative in the CELISA but 11 sera gave false positive reactions in the LFA. All samples tested were PCR negative. Of 113 samples from herds with anaplasmosis, 53 were positive in the CELISA and 50 were LFA positive.

Currently used nucleic acid amplification tests for the detection of viruses and atypicals in acute respiratory infections

For the detection of respiratory viruses conventional culture techniques are still considered as the gold standard. However, results are mostly available too late to have an impact on patient management. The latest developments include appropriate DNA- and RNA-based amplification techniques (both NASBA and PCR) for the detection of an extended number of agents responsible for LRTI. Real time amplification, the latest technical progress, produces, within a considerable shorter time, results with a lower risk of false positives. As results can be obtained within the same day, patient management with appropriate therapy or reduction of unnecessary antibiotic therapy in LRTI will be possible. A number of technical aspects of these amplification assays, and their advantages are discussed.

The availability and use of these new diagnostic tools in virology has contributed to a better understanding of the role of respiratory viruses in LRTI. The increasing importance of the viral agents, Mycoplasma pneumoniae and Chlamydophila pneumoniae in ARI is illustrated. A great proportion of ARI are caused by viruses, but their relative importance depends on the spectrum of agents covered by the diagnostic techniques and on the populations studied, the geographical location and the season. The discovery of new viruses is ongoing; examples are the hMPV and the increasing number of coronaviruses. Indications for the use of these rapid techniques in different clinical situations are discussed. Depending on the possibilities, the laboratory could optimize its diagnostic strategy by applying a combination of immunofluorescence for the detection of RSV an IFL, and a combination of real-time amplification tests for other respiratory viruses and the atypical agents. When implementing a strategy, a compromise between sensitivity, clinical utility, turn around time and cost will have to be found.

Role of cell culture for virus detection in the age of technology

Viral disease diagnosis has traditionally relied on the isolation of viral pathogens in cell cultures. Although this approach is often slow and requires considerable technical expertise, it has been regarded for decades as the "gold standard" for the laboratory diagnosis of viral disease. With the development of nonculture methods for the rapid detection of viral antigens and/or nucleic acids, the usefulness of viral culture has been questioned. This review describes advances in cell culture-based viral diagnostic products and techniques, including the use of newer cell culture formats, cryopreserved cell cultures, centrifugation-enhanced inoculation, precytopathogenic effect detection, cocultivated cell cultures, and transgenic cell lines. All of these contribute to more efficient and less technically demanding viral detection in cell culture. Although most laboratories combine various culture and nonculture approaches to optimize viral disease diagnosis, virus isolation in cell culture remains a useful approach, especially when a viable isolate is needed, if viable and nonviable virus must be differentiated, when infection is not characteristic of any single virus (i.e., when testing for only one virus is not sufficient), and when available culture-based methods can provide a result in a more timely fashion than molecular methods.

Evaluation of the Quidel QuickVue test for detection of influenza A and B viruses in the pediatric emergency medicine setting by use of three specimen collection methods

The Quidel QuickVue influenza test was compared to viral culture and reverse transcriptase PCR by the use of three different respiratory specimen types. Of 122 pediatric subjects enrolled, 59 had influenza virus infections: 44 were infected with influenza A virus and 15 were infected with influenza B virus. The sensitivity of the QuickVue test was 85% with nasopharyngeal swabs, 78% with nasal swabs, and 69% with nasopharyngeal washes. Specificities were equivalent (97% to 98%) for all three collection methods.

Swedish guidelines for the management of community-acquired pneumonia in immunocompetent adults

This document presents the evidence-based guidelines of the Swedish Society of Infectious Diseases for the management of adult immunocompetent patients with community-acquired pneumonia (CAP), who are assessed at hospital. The prognostic score 'CURB-65' is recommended for all CAP patients in the emergency room. The score provides an assessment tool for the decision regarding outpatient treatment or level of hospital supervision, the choice of microbiological investigations, and empirical antibiotic treatment. In patients with non-severe CAP (CURB-65 score 0-2) we recommend initial narrow-spectrum antibiotic treatment, orally or intravenously, primarily directed at Streptococcus pneumoniae. In those with CURB-65 score 3, penicillin G or a cephalosporin intravenously is recommended. For CURB-65 score 0-3 atypical pathogens should be covered only when they are suspected on clinical or epidemiological grounds. In patients with CURB-65 score 4-5 intravenous combination therapy with either cephalosporin/macrolide or penicillin G/fluoroquinolone is recommended. Efforts should be made to identify the CAP aetiology in order to support the ongoing antibiotic treatment or to suggest treatment alterations. Recommended measures for prevention of CAP include influenza -- and pneumococcal -- vaccination to risk groups and efforts for smoking cessation.

Comparison of the Binax NOW Flu A enzyme immunochromatographic assay and R-Mix shell vial culture for the 2003-2004 influenza season

The Binax NOW Flu A enzyme immunochromatographic assay was compared to viral culture with R-Mix shell vials for 455 nasal-wash or nasal-aspirate specimens. The overall sensitivity, specificity, positive predictive value, and negative predictive value of the assay were 64.9%, 98.4%, 89.3%, and 93.2%, respectively. However, the assay sensitivity decreased significantly with increasing patient age.

Performance characteristics of a rapid immunochromatographic assay for detection of influenza virus in children during the 2003 to 2004 influenza season

STUDY OBJECTIVE

We evaluate the performance of a rapid assay (Binax NOW) for the detection of influenza A virus in children.

METHODS

The performance of an in vitro rapid immunochromatographic assay for detection of influenza A virus was compared to viral culture in 4,383 consecutive respiratory specimens received during the 2003 to 2004 season, which included an influenza A epidemic in October and November of 2003.

RESULTS

The overall test sensitivity was 61.6% (95% confidence interval [CI] 60.3% to 63.2%) and specificity was 95.8% (95% CI 95.1% to 96.3%). In preplanned subset analyses, we found the test more sensitive in infants aged 90 days or younger (sensitivity 70.3%; specificity 96.6%) and less specific during the epidemic (sensitivity 61.7%; specificity 90.4%).

CONCLUSION

This rapid assay was highly specific for detecting influenza A in children and thus appears useful for confirming this infection. Because of its limited sensitivity, however, a negative test cannot rule out influenza A.

Rapid Tests for Influenza

A variety of antigen-capture assays are commercially available for the detection of influenza. In addition, real-time multiplex polymerase chain reaction (PCR) has been used to detect influenza A and B in clinical specimens. The commercial assays can be completed in less than 30 minutes and have a sensitivity of at least 70% and a specificity of 90%, compared with viral isolation. They are useful not only in the diagnosis and treatment of individual patients with influenza-like illness but also in surveillance for influenza, decreasing the time of nosocomial outbreaks, decreasing the use of laboratory tests, and decreasing antibiotic use in patients with influenza. Some of the rapid antigen assays, and PCR, can detect the H5N1 and H9N1 viruses. Real-time multiplex PCR also detects a variety of respiratory viruses within 6 hours, with only 1 hour of hands-on technician time. The widespread use of the rapid tests for influenza is changing the practice pattern of physicians who care for patients with influenza.