Rapid diagnostic tests for influenza

Second near-infrared fluorescent dye for lateral flow immunoassays rapid detection of influenza A/B virus

Sensitive and rapid diagnostic point of care testing (POCT) system is of great significance to prevent and control human virus infection. Here reported an immunochromatographic strip technology. The second near-infrared (NIR-II) fluorescent dye encapsulated into polystyrene (PS) nanoparticles, was integrated into a lateral flow assay platform to achieve excellent detection of influenza A/B. This surface-functionalized and mono-dispersed PS nanoparticles has been conjugated with influenza nucleoprotein monoclonal antibody as targets for influenza antigen-detection. This assay achieved the detection limit of 0.015 ng/mL for influenza A nucleoprotein and 4.3*10^-5 HAU/mL (10^2.08 TCID₅₀/mL) influenza A virus (influenza B: 0.037 ng/mL, 9.7*10^-7 HAU/mL (10^0.43 TCID₅₀/mL)). Compared with an Au-based lateral flow test strip, the strip's sensitivity is about 16-fold higher than it. Strip detection properties remain stable for 6 months under 4 °C to 30 °C storage. The assay's intra assay variation is 5.14% and the inter assay variation is 7.74%. Other potential endogenous and exogenous interfering substances (whole blood, nasal mucin, saliva, antipyretics, antihistamines and neuraminidase inhibitors) showed negative results, which verified the excellent specificity of this method. This assay was successfully applied to the POCT quantitative detection of influenza A/B virus, the sensitivity to influenza A and B viruses was 70% and 87.5% respectively, and the specificity was 100%. Therefore, these microspheres can be used as an effective material for rapid POCT detection in clinical specimens.

Immunodominant regions prediction of nucleocapsid protein for SARS-CoV-2 early diagnosis: a bioinformatics and immunoinformatics study

COVID-19 caused by SARS-CoV-2 is sweeping the world and posing serious health problems. Rapid and accurate detection along with timely isolation is the key to control the epidemic. Nucleic acid test and antibody-detection have been applied in the diagnosis of COVID-19, while both have their limitations. Comparatively, direct detection of viral antigens in clinical specimens is highly valuable for the early diagnosis of SARS-CoV-2. The nucleocapsid (N) protein is one of the predominantly expressed proteins with high immunogenicity during the early stages of infection. Here, we applied multiple bioinformatics servers to forecast the potential immunodominant regions derived from the N protein of SARS-CoV-2. Since the high homology of N protein between SARS-CoV-2 and SARS-CoV, we attempted to leverage existing SARS-CoV immunological studies to develop SARS-CoV-2 diagnostic antibodies. Finally, N_229-269, N_349-399, and N_405-419 were predicted to be the potential immunodominant regions, which contain both predicted linear B-cell epitopes and murine MHC class II binding epitopes. These three regions exhibited good surface accessibility and hydrophilicity. All were forecasted to be non-allergen and non-toxic. The final construct was built based on the bioinformatics analysis, which could help to develop an antigen-capture system for the early diagnosis of SARS-CoV-2.

Development of a multiplex isothermal amplification molecular diagnosis method for on-site diagnosis of influenza

Influenza, which is an acute respiratory disease caused by the influenza virus, represents a worldwide public health and economic problem owing to the significant morbidity and mortality caused by its seasonal epidemics and pandemics. Sensitive and convenient methodologies for the detection of influenza viruses are important for clinical care and infection control as well as epidemiological investigations. Here, we developed a multiplex reverse transcription loop-mediated isothermal amplification (RT-LAMP) with quencher/fluorescence oligonucleotides connected by a 5' backward loop (LF or LB) primer for the detection of two subtypes of influenza viruses: Influenza A (A/H1 and A/H3) and influenza B. The detection limits of the multiplex RT-LAMP assay were 103 copies and 102 copies of RNA for influenza A and influenza B, respectively. The sensitivities of the multiplex influenza A/B/IC RT-LAMP assay were 94.62% and 97.50% for influenza A and influenza B clinical samples, respectively. The specificities of the multiplex influenza A/B/IC RT-LAMP assay were 100% for influenza A, influenza B, and healthy clinical samples. In addition, the multiplex influenza A/B/IC RT-LAMP assay had no cross-reactivity with other respiratory viruses.

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.

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.

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.

A two-step protocol for isolation of influenza A (H7N7) virions and their RNA for PCR diagnostics based on modified paramagnetic particles

Annual epidemics of influenza cause death of hundreds of thousands people and they also have a significant economic impact. Hence, a need for fast and cheap influenza diagnostic method is arising. The conventional methods for an isolation of the viruses are time-consuming and require expensive instrumentation as well as trained personnel. In this study, we modified the surface of nanomaghemite (γ-Fe2 O3 ) paramagnetic core with tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane and the resulting particles were utilized for the isolation of H7N7 influenza virions. Consequently, we designed γ-Fe2 O3 paramagnetic core modified with calcium tripolyphosphate which was employed for the isolation of viral nucleic acid after virion's lysis. Both of these procedures can be performed rapidly in less than 10 min and, in combination with the RT-PCR, the whole influenza detection can be shortened to few hours. Moreover, the whole protocol could be easily automated and/or miniaturized, and thus can serve as a basis for use in a lab-on-a-chip device. We assume that magnetic isolation is an exceptional procedure which can significantly accelerate the diagnostic possibilities of a broad spectrum of diseases.

The Inability to Screen Exhibition Swine for Influenza A Virus Using Body Temperature

Agricultural fairs create an unconventional animal-human interface that has been associated with swine-to-human transmission of influenza A virus (IAV) in recent years. Early detection of IAV-infected pigs at agricultural fairs would allow veterinarians to better protect swine and human health during these swine exhibitions. This study assessed the use of swine body temperature measurement, recorded by infrared and rectal thermometers, as a practical method to detect IAV-infected swine at agricultural fairs. In our first objective, infrared thermometers were used to record the body surface temperature of 1,092 pigs at the time of IAV nasal swab collection at the end of the exhibition period of 55 agricultural fairs. IAV was recovered from 212 (19.4%) pigs, and the difference in mean infrared body temperature measurement of IAV-positive and IAV-negative pigs was 0.83°C. In a second objective, snout wipes were collected from 1,948 pigs immediately prior to the unloading of the animals at a single large swine exhibition. Concurrent to the snout wipe collection, owners took the rectal temperatures of his/her pigs. In this case, 47 (2.4%) pigs tested positive for IAV before they entered the swine barn. The mean rectal temperatures differed by only 0.19°C between IAV-positive and IAV-negative pigs. The low prevalence of IAV among the pigs upon entry to the fair in the second objective provides evidence that limiting intraspecies spread of IAV during the fairs will likely have significant impacts on the zoonotic transmission. However, in both objectives, the high degree of similarity in the body temperature measurements between the IAV-positive and IAV-negative pigs made it impossible to set a diagnostically meaningful cut point to differentiate IAV status of the individual animals. Unfortunately, body temperature measurement cannot be used to accurately screen exhibition swine for IAV.

Light Weight and Flexible High-Performance Diagnostic Platform

A flexible diagnostic platform is realized and its performance is demonstrated for early detection of avian influenza virus (AIV) subtype H1N1 DNA sequences. The key component of the platform is high-performance biosensors based on high output currents and low power dissipation Si nanowire field effect transistors (SiNW-FETs) fabricated on flexible 100 μm thick polyimide foils. The devices on a polymeric support are about ten times lighter compared to their rigid counterparts on Si wafers and can be prepared on large areas. While the latter potentially allows reducing the fabrication costs per device, the former makes them cost efficient for high-volume delivery to medical institutions in, e.g., developing countries. The flexible devices withstand bending down to a 7.5 mm radius and do not degrade in performance even after 1000 consecutive bending cycles. In addition to these remarkable mechanical properties, on the analytic side, the diagnostic platform allows fast detection of specific DNA sequences of AIV subtype H1N1 with a limit of detection of 40 × 10(-12) m within 30 min suggesting its suitability for early stage disease diagnosis.

Recognition of dual targets by a molecular beacon-based sensor: subtyping of influenza A virus

A molecular beacon (MB)-based sensor to offer a decisive answer in combination with information originated from dual-target inputs is designed. The system harnesses an assistant strand and thermodynamically favored designation of unpaired nucleotides (UNs) to process the binary targets in "AND-gate" format and report fluorescence in "off-on" mechanism via a formation of a DNA four-way junction (4WJ). By manipulating composition of the UNs, the dynamic fluorescence difference between the binary targets-coexisting circumstance and any other scenario was maximized. Characteristic equilibrium constant (K), change of entropy (ΔS), and association rate constant (k) between the association ("on") and dissociation ("off") states of the 4WJ were evaluated to understand unfolding behavior of MB in connection to its sensing capability. Favorable MB and UNs were furthermore designed toward analysis of genuine genetic sequences of hemagglutinin (HA) and neuraminidase (NA) in an influenza A H5N2 isolate. The MB-based sensor was demonstrated to yield a linear calibration range from 1.2 to 240 nM and detection limit of 120 pM. Furthermore, high-fidelity subtyping of influenza virus was implemented in a sample of unpurified amplicons. The strategy opens an alternative avenue of MB-based sensors for dual targets toward applications in clinical diagnosis.

Evaluation of the Alere I influenza A&B nucleic acid amplification test by use of respiratory specimens collected in viral transport medium

The Alere i Influenza A&B assay is a newly developed rapid molecular assay which has the potential to generate results within 15 min from sample collection. In this study, we evaluated the Alere i Influenza A&B assay by using salvaged frozen respiratory specimens that were collected in viral transport medium from children ages 10 months to 19 years. Alere i Influenza A&B assay test results were compared with viral culture and ProFlu(+) real-time reverse transcription-PCR (RT-PCR) assay results. We found that the overall sensitivity and specificity of the Alere i Influenza A&B assay were 93.3% and 94.5% for the detection of influenza A virus and 100% and 100% for the detection of influenza B virus, respectively, compared to viral culture. In comparison to ProFlu(+) real-time RT-PCR, overall sensitivity and specificity of the Alere i Influenza A&B assay for the detection of influenza A virus were 88.8% and 98.3% and 100% and 100% for detecting influenza B virus. Overall, the Alere i Influenza A&B assay performed well compared to either virus cell culture or RT-PCR.

Universal biosensor for detection of influenza virus

Influenza is a contagious disease caught by humans caused by viruses belonging to the family Orthomyxoviridae. Each year, the influenza virus infects millions of people and kills hundreds of thousands of them. Traditional diagnostic methods, such as virus propagation and isolation, antigen capture immunoassays and molecular methods are not sufficient for the detection of the influenza virus. Development of a valid diagnostic assay for quick detection (in less than an hour) of the virus, with high sensitivity, is a challenge for researchers all over the world. Here we present a new, universal immunosensor for detection of the influenza A virus. By using electrochemical impedance spectroscopy (EIS) and direct attachment of antibodies to the gold electrode the assay allows detection of the pathogen with sensitivity similar to molecular methods in relatively short time. Application of universal anti-M1 antibodies allows detection of all serotypes of influenza A virus. The simple design of the sensor facilitates miniaturization of the device and its implementation for routine diagnostics during first contact with the patient, before applying a proper treatment.

Evaluation of the SD BIOLINE Dengue Duo rapid test in the course of acute and convalescent dengue infections in a Mexican endemic region

In this study, we evaluated the performance of a rapid test, the SD BIOLINE Dengue Duo (SD BDD) kit, with a panel of serum samples from 310 Mexican patients with diagnosis of dengue infection previously confirmed by reference enzyme-linked immunosorbent assay tests. Eighty-seven negative samples from other febrile illnesses were included as controls. The SD BDD showed an overall sensitivity of 90.65% and specificity of 89.66%. No statistically significant differences were found in the sensitivity of the SD BDD kit compared between primary or secondary infections (87.05% versus 93.57%, respectively, P = 0.0761) and dengue fever or dengue hemorrhagic fever cases (90.77% versus 89.74%, respectively, P = 0.7716). However, a higher sensitivity in the acute phase of dengue infection was found compared with the convalescent phase (93.03% versus 81.82%, respectively, P = 0.0089). These results indicate that the SD BDD kit is a useful tool to diagnose dengue infections, both in primary or secondary infections and mainly during the acute phase.

Evaluation of five rapid diagnostic kits for influenza A/B virus

Influenza viruses cause seasonal epidemics associated with high morbidity and mortality. However, even during periods of epidemic prevalence, clinical diagnoses are problematic. Rapid diagnostic tests for the detection of pandemic influenza A/B virus are valuable for their ease of use. Many rapid influenza diagnostic kits were introduced recently in the Republic of Korea (ROK), including Directizen EZ Flu A and B (Becton Dickinson, Sparks, USA), Binax Now Influenza A/B antigen kit (Binax, Portland, USA), Genedia influenza Ag (Green Cross, Yongin, ROK), Humasis Influenza A/B antigen test (Humasis, Anyang, ROK), and SD Bioline rapid influenza kit (Standard Diagnostics, Yongin, ROK). The objective of this study was to evaluate the performance of these five rapid diagnostic kits. The results were compared with those of viral culture and reverse transcription (RT)-PCR. A total of 253 nasopharyngeal swabs were analyzed from 253 patients (influenza A, n=67; B, n=86; negative samples, n=100). The specimens were tested immediately by conventional influenza virus culture and RT-PCR, stored at -80°C, and tested using five rapid test kits. The performance of the five rapid tests kits varied with sensitivities between 71.0 and 82.1% and between 37.2 and 47.7% for detecting influenza A and B, respectively. For influenza A, the sensitivities of the Directizen EZ Flu A and B, Binax Now Influenza A/B antigen kit, Genedia influenza Ag, Humasis Influenza A/B antigen test, and SD Bioline rapid influenza kits were 82.1%, 71.0%, 76.1%, 79.1%, and 82.1%, respectively; those for influenza B were 40.7%, 37.2%, 40.7%, 41.8%, and 47.7%, respectively. The specificity of all rapid tests was 100%. Commercial influenza antigen detection assays are useful tools for the rapid diagnosis of influenza. However, confirmatory testing is always recommended.

Influenza and HIV: lessons from the 2009 H1N1 influenza pandemic

Influenza is a common respiratory disease in adults, including those infected with HIV. In the spring of 2009, a pandemic influenza A (H1N1) virus (pH1N1) emerged. In this article, we review the existing literature regarding pH1N1 virus infection in HIV-infected adults, which suggests that susceptibility to pH1N1 virus infection and severity of influenza illness are likely not increased in HIV-infected adults without advanced immunosuppression or comorbid conditions. The risk of influenza-related complications, however, may be increased in those with advanced immunosuppression or high-risk comorbid conditions. Prevention and treatment of high-risk comorbid conditions and annual influenza vaccination should continue to be part of HIV clinical care to help prevent influenza illness and complications. Additional information about pH1N1 vaccine immunogenicity and efficacy in HIV-infected patients would be useful to guide strategies to prevent influenza virus infection in this population.

Symptomatic predictors for 2009 influenza A virus (H1N1) infection with an emphasis for patients with a negative rapid diagnostic test

Background

The clinical diagnosis of influenza is difficult because it shares nonspecific symptoms with a variety of diseases. Emergency departments and clinics were overwhelmed by a surge of anxious patients during the 2009 influenza A virus (H1N1) outbreak. Our objective was to identify symptomatic predictors of influenza virus infection for patients with a negative rapid diagnostic test.

Methodology/Principal Findings

We conducted a retrospective review of 805 patients who presented at Chang Gung Memorial Hospital, from August 1, 2009, to September 30, 2009. Respiratory specimens from these patients were subjected to rapid influenza tests and reverse-transcription polymerase chain reactions. In total, 36% of 308 children and 23% of 497 adults were positive for 2009 influenza A virus (H1N1) infection by polymerase chain reaction or virus culture. For pediatric patients, sore throat and influenza-like illness significantly increased the odds of having 2009 influenza A virus (H1N1) infection, by more than 3-fold (95% confidence interval (CI): 1.9–7.3) and 7-fold (95% CI: 4.00–14.2), respectively. For adult patients, cough and constitutional symptoms increased the odds of having 2009 influenza A virus (H1N1) by greater than 5-fold (95% CI: 3.1–10.2) and 3-fold (95% CI: 2.1–6.7), respectively. The negative likelihood ratio of the combination of fever and cough was 0.096 (95% CI: 0.01–0.69) for children with negative results of rapid influenza diagnostic tests.

Conclusion/Significance

In influenza epidemic settings, clinicians should be aware that rapid influenza diagnostic tests are relatively insensitive for the diagnosis of influenza virus infection. For patients with negative rapid influenza diagnostic tests, those lacking fever and cough have a low probability of influenza virus infection. The management strategy should be made individually and depend on the severity of illness.

Influenza in immunocompromised patients: considerations for therapy

Influenza infection results in substantial morbidity and mortality in immunocompromised patients, and the risks for influenza and its related complications depend on the degree of immunosuppression. In addition to influenza vaccination and infection control precautions, two classes of antiviral drugs are currently approved for treatment and prophylaxis in uncomplicated infected patients. However, there are no randomized controlled trials assessing the efficacy and safety of licensed antivirals for influenza management in immunocompromised patients. The purpose of this article is to highlight some considerations for therapy in immunocompromised patients, the usefulness of vaccination for the prevention of influenza and the clinical interest in surveillance of antiviral resistance.

Viral agents causing lower respiratory tract infections in hospitalized children: evaluation of the Speed-Oligo® RSV assay for the detection of respiratory syncytial virus

Respiratory syncytial virus (RSV) is the viral agent which is more frequently involved in lower respiratory tract infections (LRTIs) in infants under 1 year of age in developed countries. A new oligochromatographic assay, Speed-Oligo® RSV, was designed and optimized for the specific detection and identification of RSV subtypes A and B. The test was evaluated in 289 clinical samples from 169 hospitalized children using an immunochromatography (IC) test, virus isolation by culture, and an in-house real-time polymerase chain reaction (RT-PCR). Other viruses causing LRTIs were investigated by cell culture or PCR-based tests. Sixty-two patients were infected by RSV (36.7%). In addition, adenovirus, influenza B, parainfluenza 2, and human metapneumovirus were detected in rates ranging from 5 to 8%. A proportion of 10.1% of the patients had mixed infections. The sensitivity, specificity, and positive and negative predictive values were, respectively, 94.9, 99.4, 98.9, and 97.4% for Speed-Oligo® RSV, 92.9, 96.3, 92.9, and 96.3% for RT-PCR/RSV, and 58.4, 98.1, 93.3, and 82.6% for IC. Our rates of viral detection and co-infection were similar to those of previously reported series. Finally, we find that Speed-Oligo® RSV is a rapid and easy-to-perform technique for the detection of RSV and the identification of subtypes A and B.

Comparison of a laboratory-developed RT-PCR and the CDC RT-PCR protocol with rapid immunodiagnostic testing during the 2009 H1N1 influenza A pandemic

We evaluated the performance of a laboratory-developed multiplex real-time reverse transcription-PCR assay (LDT rRT-PCR), the Centers for Disease Control and Prevention (CDC) 2009 H1N1 rRT-PCR protocol using the LightCycler 480 II, the multiplex xTAG Respiratory Virus Panel (xTAG RVP), and rapid immunodiagnostic testing (RIDT) using the BinaxNOW Influenza A & B to detect 2009 H1N1 with 426 nasopharyngeal swab specimens during the 2009 H1N1 pandemic. The specificity of the methods tested was ≥98%, and the individual test sensitivities were RIDT at 42.3% [95% confidence interval (CI), 31.4–54.0], LDT rRT-PCR at 98.9% (95% CI, 92.9–99.9), CDC 2009 H1N1 rRT-PCR at 78.2% (95% CI, 67.8–86.0), and xTAG RVP at 93.1% (95% CI, 85.0–97.2). A negative RIDT result should not be used to make decisions with respect to treatment or infection prevention. rRT-PCR is the preferred first-line diagnostic test for detecting 2009 H1N1 influenza A.

Complementary monoclonal antibody-based dot ELISA for universal detection of H5 avian influenza virus

BACKGROUND

Rapid diagnosis and surveillance for H5 subtype viruses are critical for the control of H5N1 infection.

RESULTS

In this study, H5 Dot ELISA, a rapid test for the detection of avian H5N1 influenza virus, was developed with two complementary H5 monoclonal antibodies. HA sequencing of escape mutants followed by epitope mapping revealed that the two Mabs target the epitope component (189th amino acid) on the HA protein but are specific for different amino acids (189Lys or 189Arg). Gene alignment indicated that these two amino acids are the most frequent types on this position among all of the H5 AIV reported in GeneBank. These two H5 Mabs were used together in a dot ELISA to detect H5 viral antigen. The detection limit of the developed test for multiple clades of H5N1 viruses, including clades 0, 1, 2.1, 2.2, 2.3, 4, 7, and 8, was less than 0.5 hemagglutinin units. The specificity of the optimized dot ELISA was examined by using 100 H5 strains, including H5N1 HPAI strains from multiple clades, 36 non-H5N1 viruses, and 4 influenza B viruses. No cross-reactivity was observed for any of the non-H5N1 viruses tested. Among 200 random poultry samples, the test gave 100% positive results for all of the twelve RT-PCR-positive samples.

CONCLUSIONS

Considering that the test is convenient for field use, this H5 Dot ELISA can be used for on-site detection of H5N1 infection in clinical or environmental specimens and facilitate the investigation of H5N1 influenza outbreaks and surveillance in poultry.

Routine use of point-of-care tests: usefulness and application in clinical microbiology

Point-of-care (POC) tests offer potentially substantial benefits for the management of infectious diseases, mainly by shortening the time to result and by making the test available at the bedside or at remote care centres. Commercial POC tests are already widely available for the diagnosis of bacterial and viral infections and for parasitic diseases, including malaria. Infectious diseases specialists and clinical microbiologists should be aware of the indications and limitations of each rapid test, so that they can use them appropriately and correctly interpret their results. The clinical applications and performance of the most relevant and commonly used POC tests are reviewed. Some of these tests exhibit insufficient sensitivity, and should therefore be coupled to confirmatory tests when the results are negative (e.g. Streptococcus pyogenes rapid antigen detection test), whereas the results of others need to be confirmed when positive (e.g. malaria). New molecular-based tests exhibit better sensitivity and specificity than former immunochromatographic assays (e.g. Streptococcus agalactiae detection). In the coming years, further evolution of POC tests may lead to new diagnostic approaches, such as panel testing, targeting not just a single pathogen, but all possible agents suspected in a specific clinical setting. To reach this goal, the development of serology-based and/or molecular-based microarrays/multiplexed tests will be needed. The availability of modern technology and new microfluidic devices will provide clinical microbiologists with the opportunity to be back at the bedside, proposing a large variety of POC tests that will allow quicker diagnosis and improved patient care.

Pandemic H1N1 and seasonal H3N2 influenza infection in the human population show different distributions of viral loads, which substantially affect the performance of rapid influenza tests

A wide range of sensitivity has been reported for rapid influenza antigen tests (RIAT). In this study, we analyzed the viral loads of 778 pandemic H1N1- and 227 seasonal H3N2-virus positive clinical specimens collected during the same period and found that viral loads in pandemic H1N1 viruses was characterized by lower copy numbers than seasonal H3N2 viruses. Among various factors including the timing of specimen collection, patient age, patient gender and subtype of influenza, we found that the subtype of influenza was the most important determinant of viral load. To investigate whether these different patterns of viral load distribution affect the clinical performance of RIAT, the RIAT reagent itself and the various virus subtypes were considered and analyzed further. Based on three strategies, including cut-off values, performance on a subset of clinical specimens and evaluated performance curve of the Espline influenza A&B-N RIAT, the clinical sensitivities were 48.7-55.9% for pandemic H1N1 and 64.0-70.5% for seasonal H3N2 viruses in this study. These results indicate that the distributions of viral loads of different influenza A subtypes substantially influence the sensitivity of RIAT for clinical specimens. The lower sensitivity of RIAT for pandemic H1N1 than seasonal H3N2 virus is mainly due to differences in viral load in clinical samples rather than a diminished capacity of RIAT itself to detect these two subtypes of influenza A viruses.

Comparison of the performance of direct fluorescent antibody staining, a point-of-care rapid antigen test and virus isolation with that of RT-PCR for the detection of novel 2009 influenza A (H1N1) virus in respiratory specimens

Although infections with the novel pandemic 2009 influenza A (H1N1) virus (A/H1N1/2009) appeared to be relatively mild during the first summer of circulation (‘off season’), there has been significant morbidity and hospitalization and several fatal cases. Thus, rapid detection of A/H1N1/2009 is crucial for efficient treatment and infection control measures. In contrast to seasonal influenza, where point-of-care (POC) rapid antigen tests and direct fluorescent antibody (DFA) staining ensure rapid detection, diagnosis of A/H1N1/2009 has so far been based on RT-PCR. This study retrospectively compared the performance of the Quidel QuickVue POC test, DFA staining and virus isolation with that of RT-PCR for A/H1N1/2009 detection in 526 respiratory specimens collected during the first wave of the outbreak from May to September 2009. A/H1N1/2009 was detected in 9.1 % (48/526) of samples. One hundred and thirty-seven of the A/H1N1/2009 PCR-negative samples were additionally tested using a RealAccurate Respiratory RT-PCR panel, revealing other respiratory viruses (mainly entero/rhino- and adenoviruses) in 42.3 % (58/137). All methods analysed detected A/H1N1/2009 with excellent specificity but different sensitivities (POC test: 18.2 %; DFA staining: 38.7 %; virus isolation: 45.7 %). Therefore, the POC test was not suitable for diagnosis, detecting A/H1N1/2009 only if present in high concentrations (corresponding median C t value=19.0; range=16.5–21.4). DFA staining was also able to detect A/H1N1/2009 in specimens with a lower virus concentration (median C t value=24.0; range=16.5–29.8). Virus isolation, which was positive after a median time of 7.5 days, was too time-consuming. In summary, DFA staining is superior to POC testing and may be appropriate for patients expected to have a rather high level of virus replication. Nevertheless, in DFA-negative specimens, A/H1N1/2009 should be excluded by RT-PCR.

Evaluation of QuickVue influenza A+B rapid test for detection of pandemic influenza A/H1N1 2009

BACKGROUND

A novel influenza A/H1N1 emerged in early 2009 and by June 2009 was declared a pandemic by WHO. Rapid influenza antigen detection tests have been used to diagnose seasonal influenza but have not been adequately evaluated for the pandemic strain among all age groups. In the Philippines, pandemic influenza A/H1N1 2009 was first detected in May 2009 and by July 2009, 3207 cases and 6 deaths were reported.

OBJECTIVES

Using RT-PCR as the gold standard, clinical sensitivity/specificity of Quidel QuickVue (QV) influenza A+B was estimated across all age groups for pandemic influenza A/H1N1 using nasal swabs in a hospital setting. Effect of age, viral titers (Ct values), and timing of collection on QV sensitivity to detect pandemic influenza A/H1N1 2009 was also determined.

STUDY DESIGN

Febrile patients with influenza-like illness (n=360) at the V. Luna General Hospital, Manila from 1 June to 31 August 2009 were included. Nasal swabs were tested using QV and RT-PCR.

RESULTS

Of 360 nasal specimens 226 (63%) were positive for pandemic influenza A/H1N1. QV sensitivity was 63% (95% confidence interval (CI): 56-69%), specificity was 96% (95% CI: 91-99%), positive predictive value was 97% (CI: 93-99%), and negative predictive value was 57% (95% CI: 49-64%). Patient's age, fever severity, presenting symptoms or number of symptoms did not significantly affect QV sensitivity, however QV sensitivity was correlated with decreasing Ct values.

CONCLUSION

QuickVue demonstrated moderate sensitivity for pandemic influenza A/H1N1 infection. There was a significant inverse association between Ct values and QV sensitivity for pandemic influenza A/H1N1.

Performance of influenza rapid point-of-care tests in the detection of swine lineage A(H1N1) influenza viruses

Background  In April 2009, an A(H1N1) influenza virus of swine lineage was detected in humans in the USA, and in just over a month has infected over 10 000 people in more than 40 countries.

Objectives  To determine the performance of the Binax Now, BD Directigen EZ, and the Quidel QuickVue influenza rapid point‐of‐care (POC) tests for the detection of the recently emerged swine lineage A(H1N1) virus.

Methods  Swine lineage A(H1N1) and human seasonal influenza strains were cultured and then diluted to specific infectivity titres. Viral dilutions were assayed by the rapid POC tests and by real‐time RT‐PCR.

Results  All three of the rapid POC tests successfully detected the swine lineage A(H1N1) viruses at levels between 10³ and 10⁵ TCID₅₀/ml (tissue culture infectious dose₅₀), with the BD Directigen test demonstrating marginally greater sensitivity than the other two tests. Viral infectivity and RNA load data for viruses at the detection limit of the rapid test kits, suggested that both the Quidel and the Binax tests were less sensitive for the detection of swine lineage A(H1N1) viruses than for human seasonal strains. In comparison the BD Directigen demonstrated similar sensitivity when detecting swine lineage A(H1N1) and human seasonal viruses.

Conclusions  The three rapid POC tests all detected the emergent swine lineage A(H1N1) virus when it was present at high virus concentrations. Early diagnosis of infection can assist in the rapid treatment. However the tests are significantly less sensitive than PCR assays and as such, negative results should be verified by a laboratory test.

The detection of influenza A and B viruses in clinical specimens using a quartz crystal microbalance

Current methods for the accurate diagnosis of influenza based on culture of the virus or PCR are highly sensitive and specific but require specialised laboratory facilities and highly trained personnel and, in the case of viral culture, can take up to 14 days to obtain a definitive result. In this study, a quartz crystal microbalance-based immunosensor (QCM) has been developed and its potential evaluated for the rapid and sensitive detection of both influenza A and B viruses in laboratory-cultured preparations and clinical samples. The effective limit for detection by QCM for stock preparations of both A/PR/8/34 and B/Lee/40 viruses was 1 × 10⁴ pfu/mL, associated with observed frequency shifts of 30 (±5) and 37 (±6.5) Hz, respectively. Conjugation of 13 nm gold nanoparticles to the detecting antibody improved the mass sensitivity of the immunosensor, resulting in a 10-fold increase in sensitivity and a detection limit of 1 × 10³ pfu/mL for both preparations, with resulting frequency shifts of 102 (±11) and 115 (±5) Hz, respectively. Detection of virus in nasal washes with this technique was achieved by overnight passage in MDCK cultures prior to analysis. A comparison of results obtained from 67 clinical samples using existing RT-PCR, shell vial, cell culture and ELISA methods showed that QCM techniques were comparable in sensitivity and specificity to cell culture methods.

Field performance of a rapid diagnostic test for influenza in an ambulatory setting

Provided test characteristics are adequate, point-of-care rapid antigen detection tests for influenza could improve the timeliness and appropriateness of clinical decisions. Our objective was to estimate the field sensitivity and specificity of the Quidel QuickVue Influenza A+B test in an ambulatory setting. The sensitivity and specificity of the Quidel QuickVue test was evaluated against reverse-transcriptase PCR (RT-PCR) on nasopharyngeal specimens collected over two consecutive influenza seasons from ambulatory patients consulting for influenza-like illness (ILI) within 7 days of ILI onset. A total of 491 patients with ILI (180 in 2006 to 2007 and 311 in 2007 to 2008) provided specimens that were tested both by PCR and by the Quidel QuickVue test. Among the 267 patients positive by PCR (55%), 52 were also positive by the QuickVue test, for an overall sensitivity of 19.5% (95% confidence interval [95% CI], 14.7% to 24.2%). Among the 221 PCR-negative patients, 2 were positive for influenza B virus by the rapid test (<1%), for an overall specificity of 99.1% (95% CI, 97.9 to 100%). The field sensitivity of the test varied little with the age or gender of the patient, immunization status, delay since the onset of symptoms, or influenza season. The sensitivity of the test was slightly but nonsignificantly higher for influenza B virus (23%) than for influenza A virus (18%). Despite its high specificity, the low sensitivity of the Quidel QuickVue Influenza A+B test is too poor to direct clinical decisions for ambulatory patients with ILI. Negative results cannot rule out the diagnosis of influenza, and in that context, this test is of questionable utility for routine application in the clinical setting.

Viral Infections

Although influenza remains indisputably the most significant viral pathogen in adults, other viruses such as respiratory syncytial virus, parainfluenza viruses, and human metapneumovirus are now recognized as significant pathogens in older populations.

Oseltamivir and zanamivir are antiviral agents that are effective for the treatment and prophylaxis of influenza A and B. For treatment and for optimal effect, therapy should be initiated within 48 h of symptom onset.

Infection with hepatitis viruses may be more severe in older adults with more fulminate disease as observed with acute hepatitis A and a more rapid progression to cirrhosis with hepatitis C.

Outbreaks of viral gastroenteritis are common in long-term care facilities, and infection may lead to death due to dehydration and oliguria.

The incidence of herpes zoster increases with advancing age and carries with it a significant risk of post herpetic neuralgia. The use of antiviral medications and corticosteroids may reduce the incidence and severity of chronic pain.

Early diagnosis of lower respiratory tract infections (point-of-care tests)

PURPOSE OF REVIEW

Respiratory tract infections are a common reason for prescribing antibiotics, although not all of these infections require such therapy. Rapid diagnosis of etiology using point-of-care tests is a potentially useful way of reducing prescriptions of both unnecessary and unnecessarily broad-spectrum antibiotics. This can also lead to the facilitation of appropriate infection control measures to prevent spread of respiratory viruses within institutions.

RECENT FINDINGS

Point-of-care tests are available for diagnosing influenza, respiratory syncytial virus, Streptococcus pneumoniae, and Legionella infections using easily obtainable specimens. Their main benefit is that results can be obtained in about 15 min with reasonable accuracy. In many situations, however, it is still important to confirm diagnosis with more accurate but slower tests such as bacterial cultures with antibacterial susceptibility testing or viral polymerase chain reaction testing.

SUMMARY

Although the sensitivities of many of the rapid diagnostic tests are moderate, when used at the time of initial consultation, they have the potential to reduce costs, length of stay, secondary spread of respiratory viruses, and inappropriate antibiotic prescribing.

Rapid diagnosis of influenza infection in older adults: influence on clinical care in a routine clinical setting

BACKGROUND

Laboratory diagnosis of influenza has previously relied on viral isolation in culture. Rapid antigen tests (RATs) are now available but few studies have examined their use in older adults under routine clinical conditions.

OBJECTIVES

To determine the utility of the RAT in older adults presenting to a large medical center and how test results impacted clinical care.

STUDY DESIGN

Retrospective chart review of patients tested for influenza during the 2003--2004 and 2004--2005 influenza seasons. Clinical data were correlated with the results of laboratory testing.

RESULTS

Eighty-four adults tested positive for influenza. Adding the results of the RAT to symptom complexes predictive of influenza significantly enhanced the ability to diagnose influenza in the acute setting. The positive predictive value of fever plus cough increased from 32% to 92% with a positive RAT. The RAT also directed appropriate antiviral therapy. 20/22 (91%) patients with a positive RAT and symptoms < or =48 h received antiviral treatment compared to only 1/12 (8%) patients with a negative RAT and a positive culture.

CONCLUSIONS

Under routine clinical conditions rapid influenza testing enhances the ability to quickly diagnose influenza and can be used to guide early treatment decisions in older adults.

RespiFinder: a new multiparameter test to differentially identify fifteen respiratory viruses

Broad-spectrum analysis for pathogens in patients with respiratory tract infections is becoming more relevant as the number of potential infectious agents is still increasing. Here we describe the new multiparameter RespiFinder assay, which is based on the multiplex ligation-dependent probe amplification (MLPA) technology. This assay detects 15 respiratory viruses in one reaction. The MLPA reaction is preceded by a preamplification step which ensures the detection of both RNA and DNA viruses with the same specificity and sensitivity as individual monoplex real-time reverse transcription-PCRs. The RespiFinder assay was validated with 144 clinical samples, and the results of the assay were compared to those of cell culture and a respiratory syncytial virus (RSV)-specific immunochromatography assay (ICA). Compared to the cell culture results, the RespiFinder assay showed specificities and sensitivities of 98.2% and 100%, respectively, for adenovirus; 96.4% and 100%, respectively, for human metapneumovirus; 98.2% and 100%, respectively, for influenza A virus (InfA); 99.1% and 100%, respectively, for parainfluenza virus type 1 (PIV-1); 99.1% and 80%, respectively, for PIV-3; 90.1% and 100%, respectively, for rhinovirus; and 94.6% and 100%, respectively, for RSV. Compared to the results of the RSV-specific ICA, the RespiFinder assay gave a specificity and a sensitivity of 82.4% and 80%, respectively. PIV-2, PIV-4, influenza B virus, InfA H5N1, and coronavirus 229E were not detected in the clinical specimens tested. The use of the RespiFinder assay resulted in an increase in the diagnostic yield compared to that obtained by cell culture (diagnostic yields, 60% and 35.5%, respectively). In conclusion, the RespiFinder assay provides a user-friendly and high-throughput tool for the simultaneous detection of 15 respiratory viruses with excellent overall performance statistics.

Performance of Binax NOW Flu A and B and direct fluorescent assay in comparison with a composite of viral culture or reverse transcription polymerase chain reaction for detection of influenza infection during the 2006 to 2007 season

The Binax NOW Flu A and Flu B (Binax NOW), direct fluorescent assay (DFA), and viral culture were evaluated and compared with a composite of viral culture or reverse transcription polymerase chain reaction (RT-PCR). Participants with medically attended acute respiratory illness were identified through active surveillance during the 2006 to 2007 season, and consenting individuals (n=932) were tested for influenza by culture and RT-PCR. Physicians ordered a rapid antigen test (Binax NOW [n=73] or DFA [n=70]) according to their clinical judgment. The Binax NOW detected 11 of 18 influenza infections (sensitivity, 61%; 95% confidence interval [CI], 36-83%), whereas DFA detected 17 of 21 influenza infections (sensitivity 81%, 95% CI, 58-95%). Compared with culture/RT-PCR, specificity of both Binax NOW and DFA was 100%. During the 2006 to 2007 influenza season, DFA and Binax NOW demonstrated high specificity but failed to identify a substantial proportion of influenza infections.

Community-acquired viral pneumonia

Advanced age often is associated with functional and immunologic decline and chronic cardiopulmonary diseases that predispose to pneumonia when viral infection occurs. Influenza virus remains the primary viral pathogen in the elderly, although the impact of the other respiratory viruses remains to be defined. The clinical syndromes associated with respiratory viruses frequently are indistinguishable from one another or bacterial pathogens; often, viral illness in older adults exacerbates underlying conditions, complicating diagnosis. Antiviral therapy is available for influenza A and B; specific viral diagnosis, particularly with the use of rapid antigen detection, may be useful for clinical management. Treatment for other viruses primarily is supportive.

Point‐of‐care tests for lower respiratory tract infections

Many lower respiratory tract infections (LRTIs) are caused by organisms that do not require antibiotics or could be safely treated with narrow-spectrum antibiotics. Reducing the unnecessary use of antibiotics, particularly broad-spectrum agents, could reduce costs and side effects and delay the emergence of antibiotic-resistant organisms. Various point-of-care tests are becoming available to help clinicians identify the cause of LRTIs at the time of consultation. Point-of-care tests can be used to diagnose influenza, pneumococcal infections, Legionella and respiratory syncytial virus infections, thus allowing early decisions to be made on appropriate management.

Diverging trends for lower respiratory infections in non-Aboriginal and Aboriginal children

AIM

To investigate temporal trends in admission rates for acute lower respiratory infections (ALRI) in a total population birth cohort of non-Aboriginal and Aboriginal children.

METHODS

Retrospective analysis of linked population-based data using the Western Australian Data Linkage System. All singleton live births in Western Australia between 1990 and 2000 were included. Hospital admission rates per 1000 live births for ALRI before age 2 years and linear time trends for ALRI admission rates were investigated.

RESULTS

ALRI admission rates were 7.5 (95% confidence interval (CI) 7.2-7.7) times higher in Aboriginal than non-Aboriginal children (337 vs. 45 per 1000 live births); pneumonia rates were 13.5 (95% CI 12.8-14.4) times higher and bronchiolitis rates were 5.8 (95% CI 5.3-6.0) times higher. ALRI admission rates rose in non-Aboriginal children (<12 months, 6%/year, P<0.002; 12-23 months, 11%/year, P<0.001) but declined in Aboriginal children aged 12-23 months (4%/year, P=0.003). Bronchiolitis rates rose in all children, especially non-Aboriginal infants aged <12 months (13%/year, P<0.001), while pneumonia rates rose in non-Aboriginal children but declined in Aboriginal children. Declines in bronchitis and asthma were also noted.

CONCLUSION

There has been an increase in incidence of bronchiolitis before age 12 months. For children aged 12-23 months a diagnostic shift from asthma and bronchitis to bronchiolitis and changes in health service utilisation are likely explanations for diverging temporal trends. The continuing disparity between Aboriginal and non-Aboriginal children needs to be addressed and appropriate preventative measures for ALRI, and in particular bronchiolitis, are urgently needed.

Performance of Directigen flu A+B enzyme immunoassay and direct fluorescent assay for detection of influenza infection during the 2004-2005 season

Early diagnosis of influenza infection is needed to optimize the benefit of prescribing antiviral drugs. However, the accuracy of rapid tests is highly variable. This study evaluated the performance of Directigen flu A+B enzyme immunoassay (EIA) and direct fluorescent assay (DFA) during the 2004-2005 influenza season. Participants with medically attended acute respiratory illness were identified through an active surveillance. Consenting patients (n=818) were enrolled and cultured for influenza. Physicians ordered a rapid antigen test (EIA or DFA) according to their clinical judgment. Physicians ordered rapid tests with EIA (n=109), DFA (n=86), or both (n=9) in 204 patients with acute respiratory illness who were also cultured for influenza. The EIA detected 18 of 43 influenza infections (sensitivity, 42%; 95% confidence interval [CI], 28-57%), whereas DFA detected 26 of 38 influenza infections (sensitivity, 68%; 95% CI, 53-81%). Compared with culture, specificity of both EIA and DFA was 96%. During the 2004-2005 influenza season, both the EIA and DFA had low sensitivity and failed to detect influenza in many patients.

Performance of six influenza rapid tests in detecting human influenza in clinical specimens

BACKGROUND

The rapid diagnosis of influenza can alter the management of a patient's illness, resulting in reduced antibiotic usage, correct use of influenza antivirals and reduced length of stay in hospital emergency departments. The rapid tests have also been used to detect outbreaks in institutions and may play a role in pandemic influenza control.

OBJECTIVES

To test six different rapid influenza tests, in a head-to-head comparison for the detection of seasonal influenza types A and B, compared to laboratory-based tests.

STUDY DESIGN

One hundred and seventy-seven clinical specimens taken from mostly paediatric patients between June and October 2006 were tested using six influenza diagnostic tests and three laboratory-based techniques (immunofluorescence, cell culture and real-time RT-PCR).

RESULTS AND CONCLUSION

Compared with cell culture, five of the rapid tests (Binax Now Influenza A&B, Directigen EZ Flu A+B, Denka Seiken Quick Ex-Flu, Fujirebio Espline Influenza A&B-N, and Quidel QuickVue Influenza A+B Test) demonstrated a similar influenza A sensitivity of between 67-71% and a specificity of 99-100%, however one rapid test (Rockeby Influenza A Antigen Test) had a significantly lower influenza A sensitivity of only 10% (specificity was 100%). For the five kits that detected influenza B antigen, sensitivity was considerably lower than that seen for influenza A (sensitivity for all the kits was 30%), although the number of specimens containing influenza B viruses was low.

Simultaneous detection of five different DNA targets by real-time Taqman PCR using the Roche LightCycler480: Application in viral molecular diagnostics

One of the most interesting aspects of real-time PCR based on the detection of fluorophoric labeled oligonucleotides is the possibility of being able to detect conveniently multiple targets in the same PCR reaction. Recently, Roche Diagnostics launched a real-time PCR platform, the LightCycler480 (LC480), which should be well suited for multiplex real-time PCR analysis. In this paper the performance of the LC480 and accompanying software for the detection of five different targets was analyzed. Target DNAs mixed at equimolar concentrations were detected reproducibly and quantitatively. In addition, mixing different concentrations of the five targets demonstrated that the LC480 is capable of providing quantitative results for a mixture of DNA sequences without losing sensitivity. When applied to the practice of molecular diagnosis of four respiratory viral infections the multiplex assay showed almost complete concordance with corresponding single-target PCRs. The application of multiplex PCR for the detection of multiple pathogens within the same sample will provide a major contribution to the efficiency, logistics and cost-effectiveness of molecular diagnostics.

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.

Virus-inducible reporter genes as a tool for detecting and quantifying influenza A virus replication

The use of influenza A virus-inducible reporter gene segments in detecting influenza A virus replication was investigated. The RNA polymerase I promoter/terminator cassette was used to express RNA transcripts encoding green fluorescence protein or firefly luciferase flanked by the untranslated regions of the influenza A/WSN/33 nucleoprotein (NP) segment. Reporter gene activity was detected after reconstitution of the influenza A virus polymerase complex from cDNA or after virus infection, and was influenza A virus-specific. Reporter gene activity could be detected as early as 6 h post-infection and was virus dose-dependent. Inhibitory effects of antibodies or amantadine could be detected and quantified rapidly, providing a means of not only identifying influenza A virus-specific replication, but also of determining the antigenic subtype as well as antiviral drug susceptibility. Induction of virus-specific reporter genes provides a rapid, sensitive method for detecting virus replication, quantifying virus titers and assessing antiviral sensitivity as well as antigenic subtype.

A multi-centre pilot proficiency programme to assess the quality of molecular detection of respiratory viruses

Objectives

To assess the quality of molecular detection of respiratory viruses in clinical diagnostic laboratories.

Study design

Respiratory virus proficiency panels were produced from diluted stocks of respiratory viruses provided and tested by four reference laboratories. The panels consisted of strong positive, positive, low positive and negative samples for influenza viruses A and B, respiratory syncytial virus, parainfluenza viruses 1 and 3, adenovirus serotypes 4 and 7, human rhinovirus serotypes 16, 72 and 90, human coronaviruses OC43 and 229E. The panels were sent to 17 participants; results and information on methodology was collected.

Results

All laboratories returned results, of which five submitted complete data sets. So, for analysis all results were combined. Samples were correctly identified by participants in 93.75%, 76.75% and 47.03% for the high positive, positive and low positive samples, respectively. One false positive was reported for all data sets (1.1%). The overall score for all assays using different methodologies was 78.8%. Laboratory performance was not dependant on methodology as all in-house methodologies could achieve optimal results, but dependant on careful optimisation and procedures specific to the laboratory.

Conclusions

The first proficiency panel showed that in general all participants performed well. Although, it also highlights areas for improvement for all participants in order to generate robust results for use in clinical diagnostics.

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.