Comparison of a new neuraminidase detection assay with an enzyme immunoassay, immunofluorescence, and culture for rapid detection of influenza A and B viruses in nasal wash specimens

Simple, rapid detection of influenza A (H1N1) viruses using a highly sensitive peptide-based molecular beacon

A peptide-based molecular beacon (PEP-MB) was prepared for the simple, rapid, and specific detection of H1N1 viruses using a fluorescence resonance energy transfer (FRET) system. The PEP-MB exhibited minimal fluorescence in its "closed" hairpin structure. However, in the presence of H1N1 viruses, the specific recognition of the hemagglutinin (HA) protein of H1 strains by the PEP-MB causes the beacon to assume an "open" structure that emits strong fluorescence. The PEP-MB could detect H1N1 viruses within 15 min or even 5 min and can exhibit strong fluorescence even at low viral concentrations, with a detection limit of 4 copies.

Colorimetric detection of influenza A (H1N1) virus by a peptide-functionalized polydiacetylene (PEP-PDA) nanosensor

​We developed a peptide-functionalized polydiacetylene nanosensor for pH1N1 virus detection with the naked eye.

Developments in immunologic assays for respiratory viruses

In most hospitals, clinics, and doctor's offices, immunologic assays are the only tests performed on site for the diagnosis of respiratory viruses. More than other methods, immunoassays have been shown to affect patient management and save costs, aiding early administration of antiviral therapy, reduction in unnecessary tests and antibiotics, and earlier discharges. This article discusses the major immunologic methods employed for respiratory virus diagnosis, recent developments in immunoassays and sample collection, and current test algorithms.

Detection and differentiation of four poultry diseases using asymmetric reverse transcription polymerase chain reaction in combination with oligonucleotide microarrays

Asymmetric reverse transcription polymerase chain reaction (RT-PCR) and microarrays were combined to distinguish 4 viruses, including Avian influenza virus (AIV), Newcastle disease virus (NDV), Infectious bronchitis virus (IBV), and Infectious bursal disease virus (IBDV), and hemagglutinin (HA) subtypes H5, H7, and H9, and neuraminidase (NA) subtypes N1 and N2 of AIV. The AIV matrix protein (M), and HA and NA genes, IBV nucleoprotein (NP) gene, NDV NP gene, and IBDV A fragment gene were cloned into plasmids. These genes were amplified from these positive recombinant plasmids, which included the inserted target genes by PCR. The PCR products were purified and printed on the amino-modified slides as the probes. RNA was extracted from samples and labeled by asymmetric RT-PCR using a cyanine (Cy)3-labeled primers. The labeled complementary (c)DNA was hybridized to the probes immobilized on the glass slides. After hybridization, the microarrays were scanned, and the hybridization pattern agreed perfectly with the known location of each probe. No cross-hybridization could be detected. Results demonstrated that microarray based on asymmetric RT-PCR is an effective way to distinguish AIV, IBV, NDV, and IBDV simultaneously.

Comparison of the performance of the rapid antigen detection actim Influenza A&B test and RT-PCR in different respiratory specimens

Nowadays, influenza antigen detection test kits are used most frequently to detect influenza A or B virus to establish the diagnosis of influenza rapidly and initiate appropriate therapy. This study was conducted to evaluate the performance of the actim Influenza A&B test (Medix Biochemica). Overall, 473 respiratory specimens were analysed in the actim Influenza A&B test and the results were compared with those from an RT-PCR assay; 461 of these samples originated from paediatric patients aged 7 weeks to 6.5 years either with influenza-related symptoms or from the intensive care unit, and 12 samples originated from adults with underlying lung or haematological diseases. Diagnosis of influenza A or B virus could be established using the actim Influenza A&B test (9/473 samples for influenza A virus and 6/473 for influenza B virus). RT-PCR revealed 23 patients with influenza virus (13/473 for influenza A virus and 10/473 for influenza B virus). The sensitivity and specificity of the actim Influenza A&B test were 65 and 100 % compared with the RT-PCR assay. However, 32 external quality assessment samples containing seven different strains of influenza A subtypes H1N1 and H3N2 and the avian H5N1 were detected correctly by the actim Influenza A&B test. No cross-reactivity to a range of bacterial, fungal and other viral pathogens was observed. In conclusion, the actim Influenza A&B test is reliable for positive results due to its high specificity. Nevertheless, negative results from this test need to be confirmed by a more sensitive assay because of the low sensitivity observed with diagnostic samples.

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.

Role of the laboratory in diagnosis of influenza during seasonal epidemics and potential pandemics

Laboratory diagnosis of influenza is critical to its treatment and surveillance. With the emergence of novel and highly pathogenic avian influenza viruses, the role of the laboratory has been further extended to include isolation and subtyping of the virus to monitor its appearance and facilitate appropriate vaccine development. Recent progress in enhancing testing for influenza promises to both improve the management of patients with influenza and decrease associated health care costs. The present review covers the technological characteristics and utilization features of currently available diagnostic tests, the factors that influence the selection of such tests, and the developments that are essential for pandemic preparedness.

[Diagnosis of viral respiratory infections]

More than 80% of the cases of respiratory infections in children are of viral origin. Viral culture has been the reference method for the diagnosis of viral respiratory infections for years, but there is now a tendency to replace viral culture by molecular biology techniques, notably real-time PCR-based assay, because of its excellent sensitivity and good feasibility. Currently in most laboratories, however, diagnosis of viral respiratory infections is still done using techniques based on detection of viral antigens, especially immunofluorescence assays. Rapid diagnostic tests for use outside of laboratories are now available on the open market, and even if their sensitivity remains lower than that of other techniques, it is likely that they will become widely used, especially in doctors' offices, in the near future. New methods for the diagnosis of viral infections based on DNA microarray technologies are currently under investigation and appear to be very promising.

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.

Diagnostic virologique des infections respiratoires

Les infections respiratoires de l'enfant sont à 80 % d'origine virale. La culture cellulaire était la technique de référence pour le diagnostic de ces infections mais cette technique tend à être supplantée par les techniques de biologie moléculaire et notamment la PCR en temps réel en raison de son excellente sensibilité et sa bonne praticabilité. Cependant, en pratique courante et dans la plupart des laboratoires, le diagnostic des infections virales respiratoires reste réalisé à l'aide de techniques reposant sur la mise en évidence des antigènes viraux notamment en immunofluorescence. Des tests de diagnostic rapide ou « doctors–tests », praticables en dehors d'un laboratoire, sont actuellement disponibles sur le marché, leur sensibilité reste inférieure à celle des autres techniques mais la généralisation de l'usage de ces tests notamment en cabinet médical est probable dans les années à venir. De nouvelles techniques de diagnostic des infections respiratoires reposant sur l'utilisation de puce à ADN sont en cours de mise au point et semblent très prometteuses.

Medically attended pediatric influenza during the resurgence of the Victoria lineage of influenza B virus

OBJECTIVES

During the 2002-2003 season, a new variant of influenza B co-circulated with influenza A viruses. This study examines the characteristics and outcomes of children with influenza A and B virus infection vs. other acute respiratory illnesses.

METHODS

A retrospective chart review was performed on children with laboratory-confirmed influenza infection, and influenza negative acute respiratory illnesses that prompted a hospital visit.

RESULTS

Children with influenza were more often previously healthy and presenting with upper respiratory symptoms, while influenza negative patients typically had underlying medical conditions, and lower respiratory tract disease. Children with influenza B were older, were more likely to be in school, and presented with myositis more frequently than those with influenza A. A third of children with influenza A, and 42% with influenza B required hospitalization. The highest hospitalization rates were in infants under one year. No healthy children, and only 15% of those with chronic medical problems, had received influenza vaccine. Vaccine efficacy was estimated to be 82.6%.

CONCLUSIONS

Most children with influenza were previously healthy. Overall, a third of children with influenza required hospitalization. Influenza A and B were clinically indistinguishable, except for older age and higher incidence of myositis in patients with influenza B. Influenza vaccine coverage in both healthy and high-risk children was low.

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.

Commercial Immunoassay Kits for the Detection of Influenza Virus Type A: Evaluation of Their Use with Poultry

Five antigen capture immunoassay test kits, Directigen Flu A (Becton Dickinson), QuickVue Influenza test kit (Quidel), FLU OIA (ThermoBiostar), Zstat Flu (ZymeTx, Inc.) and NOW FLU A Test (Binax) were used to detect avian influenza virus (AIV) in clinical specimens as per manufacturers' protocols. Each kit was shown to be specific for AIV propagated in embryonating chicken eggs (ECE); other respiratory viruses of poultry tested gave negative results. The Directigen Flu A kit proved to be 10-fold more sensitive than the other kits, capable of detecting 10(4.7) mean embryo lethal dose (ELD50)/ml in allantoic fluid; this is more sensitive than the hemagglutination test using chicken erythrocytes. None of the kits proved to be sufficiently sensitive to reliably detect AIV in oropharyngeal and cloacal swabs collected from chickens experimentally infected with AIV subtype H6N2. In two different experiments, individual swabs and pools of five or six swabs were tested. By virus isolation, 39 individual oropharyngeal swabs tested positive for AIV, but Directigen and Flu OIA only detected 2/39 and NOW FLU A 1/39. Zstat and QuickVue did not detect any. Five individual cloacal swabs positive by virus isolation were negative with all five kits. In a second experiment using pools of five swabs, 26 swab pools were positive by virus isolation and 5/26 were positive by Directigen, the only kit to provide any positive results. Five cloacal swab pools were also positive by virus isolation and 1/5 was positive by Directigen; all other test kits were negative. All of these experiments were performed using the H6N2 subtype of AIV. The results are disappointing, as the kits have proven to be insensitive for detecting AIV when compared with the gold standard, virus isolation. This limits their use in diagnostic field investigations. Individual or groups of chickens could be assumed to be positive for AIV if positive by any of the kits, but a negative result with any of the kits would not prove that birds were AIV free.

Management of acute bronchitis in healthy adults

Acute respiratory infections (ARIs) are the most common infections in humans, accounting for half of all acute conditions each year in the United States. Acute bronchitis episodes represent a significant portion of these illnesses. This article focuses on acute bronchitis in otherwise healthy individuals.

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

The performance of a new rapid lateral-flow chromatographic membrane immunoassay test kit for detection of influenza virus was evaluated and compared to that of viral culture in respiratory secretions collected from 400 adults and children seen at three large university hospitals during the recent 2003 influenza season. The rapid test provided results in 15 min, with excellent overall performance statistics (sensitivity, 94.4%; specificity, 100%; positive predictive value, 100%; negative predictive value, 97.5%). Both influenza A and B type viruses were reliably detected, with no significant difference in performance statistics noted by influenza virus type or by the center performing the test.

Comparison of the directigen flu A+B membrane enzyme immunoassay with viral culture for rapid detection of influenza A and B viruses in respiratory specimens

The performance of a commercially available, rapid membrane enzyme immunoassay for influenza A and B virus detection was compared to that of viral culture in 4,092 respiratory specimens collected from patients presenting with respiratory symptoms during the 2002-2003 influenza season. The test's overall sensitivity was 43.83%, lower than previously reported but similar for detection of both influenza A and B viruses (42.98 versus 44.76%). However, specificity, 99.74%, was excellent for both influenza A and B viruses (99.82 versus 99.92%). These values make this test a very good confirmatory test when clinical suspicion is high, but a less accurate screening test for large populations.

Sensitivity of respiratory virus culture when screening with R-mix fresh cells

Use of R-Mix Fresh Cells has been shown to be a rapid and sensitive method for the detection and identification of respiratory viruses. We prospectively evaluated the impact of incorporation of R-Mix shell vials on the sensitivity and time to detection of seven respiratory viruses recovered in a comprehensive culture during the course of an entire respiratory season in a high-volume clinical laboratory. In this study, R-Mix shell vials were used as part of the culture of 3803 respiratory specimens. A total of 428 respiratory viruses were recovered. Staining of R-Mix vials after overnight incubation allowed initial detection of 274 of 279 influenza viruses, 33 of 38 parainfluenza viruses, 35 of 51 adenoviruses, and 52 of 60 respiratory syncytial viruses (RSVs). The time to reporting of all positive cultures after in-lab specimen receipt was 2.9 days on average and those initially detected in R-Mix cells were reported in 2.3 days on average. A combination of direct fluorescent-antibody (DFA) staining and virus culture was performed on a subset of 711 respiratory specimens. Of 152 viruses identified, 57 were observed only with DFA testing (55 RSV and 2 influenza A viruses) and 31 were recovered only in cell culture. After overnight incubation, R-Mix cells detected 87.1% of respiratory viruses not observed by DFA testing and 96.9% of viruses positive by both methods. The sensitivities of DFA testing and R-Mix cells for identification of influenza viruses were 70.5% and 96.7%, respectively. The R-Mix method detected influenza virus in 18 samples that were negative by DFA testing.

New point of care test is highly specific but less sensitive for influenza virus A and B in children and adults

The importance of rapid diagnosis of influenza has increased with the availability of neuraminidase inhibitors, which need to be commenced within 48 hr of symptom onset. Furthermore, the recent development of influenza-like clinical syndromes with novel aetiologies (severe acute respiratory syndrome, SARS) has increased the need for rapid and accurate near-patient diagnosis. A new, modified point of care (POC) diagnostic test (ZstatFlu) was assessed on 469 nasopharyngeal aspirates (NPAs) and 260 nose/throat swabs (TS) taken from children and adults. The test was specific (77-98%) for all specimen types for influenza virus A and B, depending upon incubation conditions. However, it was less sensitive, detecting 65-77% of specimens confirmed as positive on culture, direct immunofluorescence or PCR testing. A positive test is useful, for both directing initiation of therapy in the clinician's office, and making a positive diagnosis of influenza in patients with influenza-like clinical syndromes.

Microsphere-based duplexed immunoassay for influenza virus typing by flow cytometry

We have developed a rapid, duplexed microsphere-based immunoassay for the characterization of influenza virus types that has the potential to overcome many of the limitations of current detection methods. The assay uses microspheres of two sizes, each coupled to an influenza type A- or type B-specific monoclonal antibody (MAb), to capture influenza viruses in the sample. A cocktail of fluorescently labeled, influenza-specific polyclonal antibodies then binds the captured viruses. The sandwich complexes are measured using a multiparameter flow cytometer. The assay can distinguish between influenza types A and B in a single reaction with good reproducibility and high sensitivity. Detection sensitivity is much higher than that of commercially available influenza diagnosis quick kits: the FLU OIA (Thermo Biostar) kit and the Directigen Flu A+B kit (Becton Dickinson). The multiplexing capabilities of the current assay, which are not possible with enzyme-linked immunosorbent assay (ELISA) and the commercially available kits, reduce sample handling and consume fewer costly reagents. This assay represents a more efficient and sensitive method of characterizing influenza types. With inclusion of influenza subtype-specific antibodies as capture antibodies, this microsphere-based immunoassay can be expanded to differentiate among influenza types and subtypes in a single reaction to improve world-wide influenza surveillance.

Comparison of the Directigen flu A+B test, the QuickVue influenza test, and clinical case definition to viral culture and reverse transcription-PCR for rapid diagnosis of influenza virus infection

The diagnostic performances of the clinical case definition of influenza virus infection based on the combination of fever and cough and of two rapid influenza diagnostic tests, the Directigen Flu A+B test (Directigen; BD Diagnostic Systems, Sparks, Md.) and the QuickVue influenza test (QuickVue; Quidel, San Diego, Calif.), were compared to those of viral culture and an in-house reverse transcription (RT)-PCR during the 2000-2001 flu season. Two hundred consecutive nasopharyngeal aspirates were analyzed from 192 patients, including 122 adults and 70 children. Viral culture identified influenza virus A in 16 samples and influenza virus B in 55 samples, whereas RT-PCR identified influenza virus A in 21 samples and influenza virus B in 64 samples. When RT-PCR was used as the reference standard, the likelihood ratios for a positive test were 40.0 for Directigen, 8.6 for QuickVue, and 1.4 for the combination of fever and cough, whereas the likelihood ratios for a negative test were 0.22, 0.16, and 0.48, respectively. Our study suggests that (i). the poor specificity (35 to 58%) and the poor positive predictive value (41 to 60%) of the clinical case definition of influenza preclude its use for prediction of influenza virus infections during epidemics, especially when infection control decision making in the hospital setting is considered; (ii). Directigen has a higher diagnostic yield than QuickVue but is associated with a larger number of invalid results; (iii). the sensitivities of the rapid diagnostic tests are significantly lower with samples from adults than with samples from children, with the rates of false-negative results reaching up to 29%; and (iv). RT-PCR detects more cases of influenza than viral culture, and this greater accuracy makes it a more useful reference standard.

Comparison of the Denka-Seiken INFLU A.B-Quick and BD Directigen Flu A+B kits with direct fluorescent-antibody staining and shell vial culture methods for rapid detection of influenza viruses

The INFLU A.B-Quick and Directigen Flu A+B enzyme immunoassays were compared with direct immunofluorescence and cell culture for detection of influenza A and B viruses in a total of 255 patient specimens. Both assays identified 23 of 42 influenza A viruses (sensitivity, 54.8%; specificity, 100%; positive predictive value [PPV], 100%; negative predictive value [NPV], 91.8%). The INFLU A.B-Quick assay identified 10 of 16 influenza B viruses (sensitivity, 62.5%; specificity, 99.6%; PPV, 90.9%; NPV, 97.5%), and the Directigen Flu A+B assay detected 9 of 16 influenza B viruses (sensitivity, 56.3%; specificity, 99.6%; PPV, 90%; NPV, 97.1%).

Comparison of lateral-flow immunoassay and enzyme immunoassay with viral culture for rapid detection of influenza virus in nasal wash specimens from children

The performance of two commercially available rapid test kits for influenza virus detection was compared to that of viral culture by using 356 nasal wash specimens collected during the 2001 to 2002 influenza season. Overall, the two rapid tests were easy to perform and showed comparable sensitivities (70.4 and 72.2%) and specificities (97.7 and 98.3%); for both test kit groups, most of the specimens that yielded false-negative results were found to be growing influenza B virus.

Evaluation of a rapid test (QuickVue) compared with the shell vial assay for detection of influenza virus clearance after antiviral treatment

QuickVue influenza rapid diagnostic test (Quidel Corp., San Diego, CA, USA) was compared with the classical shell vial assay for evaluation of influenza virus clearance in patients treated with antiviral drugs. The shell vial assay was carried out on nasopharyngeal samples obtained from volunteers for a neuraminidase-inhibitor clinical trial protocol with 24 h or less from the onset of symptoms of influenza before the use of antiviral (day 1). Follow-up included samples collected after 24 and 72 h of therapy (day 2 and 4). The rapid test was retrospectively carried out in frozen samples. Test results on 99 samples from 33 adults were compared and the shell vial assay was considered the gold standard. The overall rate of detection for the shell vial assay was 39.4% and for QuickVue was 35.5%, with a concordance of 79.8%. The sensitivity obtained for QuickVue was 74.4% and the specificity was 82.7%. Comparison of test results day by day in the follow-up resulted: day 1, higher sensitivity of QuickVue test (85.5%, 24/29); day 2, agreement on positive and negative results between QuickVue and shell vial was 60.6% (20/33); day 4, all test results in samples collected after 72 h of therapy were negative. The QuickVue test showed good sensitivity for the diagnosis of influenza-like illnesses. This rapid test kit can be an alternative tool for interventions in disease management.

Use of induced sputum for the diagnosis of influenza and infections in asthma: a comparison of diagnostic techniques

BACKGROUND

Influenza (Flu) and respiratory syncytial virus (RSV) are important viral pathogens that cause lower respiratory tract infections and severe exacerbations of asthma. Molecular biological techniques are permitting a rapid and accurate diagnosis of infections caused by respiratory pathogens, and have typically been applied to upper respiratory samples. Sputum induction provides an opportunity to directly sample secretions from the lower respiratory tract.

OBJECTIVES/STUDY DESIGN

To determine the role of induced sputum reverse-transcription polymerase chain reaction (RT-PCR) in the detection of respiratory pathogens and compare this with detection using serology and immunofluorescent antigen (IFA) testing, we recruited 49 adults from emergency room with exacerbations of asthma. After a medical assessment and spirometry, sputum was induced using ultrasonically nebulised normal saline. Sputum was assayed using IFA and RT-PCR for flu and RSV. Flu serology was performed acutely and at convalescence, 4-5 weeks later.

RESULTS

Influenza A or B was detected in 24% of the samples by PCR, significantly more than the nine cases detected using serology and the one case using IFA (P<0.05). RSV was detected in 37% of samples using PCR and 20% by IFA (P<0.05).

CONCLUSION

The combination of induced sputum and RT-PCR provides a useful means of detecting respiratory infection. The technique is safe in both adults and children, and RT-PCR is more sensitive than conventional serology and IFA. The improved sensitivity of induced sputum RT-PCR also permits a more rapid diagnosis and the opportunity of early administration of effective treatments.

Rapid diagnostic tests for influenza

In recent years, seven rapid tests for influenza have become commercially available. These tests offer the promise of making rapid influenza diagnosis much more widely available than in the past, when rapid diagnosis could be made only by fluorescent antibody staining, a demanding technique available only in advanced laboratories. Two of the rapid tests have waived status under the Clinical Laboratory Improvements Amendments of 1988. This article describes each of the seven tests and reviews English-language publications that have evaluated the performance of these tests on specimens from children. A discussion of the implications of the tests for clinical decision-making is included.

Influenza diagnosis and treatment in children: a review of studies on clinically useful tests and antiviral treatment for influenza

BACKGROUND

Prompt testing for influenza can help guide clinical management of patients with suspected influenza. Three antiviral medications, amantadine, oseltamivir and zanamivir, are approved for treatment of influenza in children. Rimantadine and ribavirin have also been used.

OBJECTIVES

To review the published evidence on clinically useful diagnostic tests and antiviral treatment for influenza virus infections in children.

METHODS

Studies published from 1966 through September 2002 were reviewed on clinical diagnosis, immunofluorescence and rapid influenza tests and on antiviral treatment of influenza virus infections among pediatric populations.

RESULTS

No studies assessed the accuracy of clinical diagnosis of influenza in children compared with viral culture. Compared with viral culture, direct immunofluorescence antibody and indirect immunofluorescence antibody tests for influenza had fair to moderate median sensitivities and high median specificities, whereas rapid influenza diagnostic tests had moderate median sensitivities and moderately high median specificities. No randomized, placebo-controlled studies were found of amantadine or rimantadine for treatment of influenza A. In a few separate controlled studies, oseltamivir, zanamivir and ribavirin each reduced symptom duration of influenza compared with placebo.

CONCLUSIONS

Additional data are needed about the accuracy of clinical diagnosis of influenza in children. Although direct immunofluorescence antibody staining, indirect immunofluorescence antibody staining and rapid tests are moderately to reasonably accurate in detecting influenza virus infections in children, physicians should use clinical judgment and local surveillance data about circulating influenza viruses when interpreting test results. Further controlled studies of the efficacy, adverse effects and emergence of antiviral resistance during treatment of influenza are needed for all of the antiviral drugs.

The pathogenesis and management of influenza virus infection in organ transplant recipients

Infection with influenza viruses poses specific problems in adult and pediatric organ transplant recipients, including a higher rate of pulmonary and extra-pulmonary complications. Also, data suggest that influenza is associated with acute cellular rejection and chronic allograft dysfunction. The main strategy of influenza prevention has been influenza immunization in order to stimulate local and systemic antibodies. However, studies have shown that antibody response to inactivated influenza vaccine is decreased in all groups of organ transplant recipients. A live attenuated influenza virus vaccine is nearing approval in the United States. However, studies are needed in organ transplant recipients to determine whether the live attenuated influenza virus vaccine can enable these patients to mount a protective immune response and what degree of protection or amelioration of illness is provided by such vaccine. It is also important to verify the safety of this vaccine in organ transplant recipients because live virus may cause severe disease in these patients. Therefore, other modalities of prevention against influenza, such as chemoprophylaxis with antiviral drugs, should be considered in this patient population. The current review provides an overview of the incidence, clinical manifestations, and strategies for the prevention and management of influenza in organ transplant recipients.

Evaluation of a new dot blot enzyme immunoassay (directigen flu A+B) for simultaneous and differential detection of influenza a and B virus antigens from respiratory samples

We report a prospective evaluation of a new dot blot enzyme immunoassay (EIA) method for the direct, rapid, qualitative, simultaneous, and differential detection of the influenza A (IA) and B (IB) virus antigen in different respiratory samples. The EIA method was compared with the shell vial culture system (MDCK cell line) used with the same samples. We studied 160 samples from 93 (58.1%) pediatric patients (hospital emergency room) and from 67 (41.9%) adult patients (sentinel network). Seventy-four(46.2%) samples were considered positive; of them, 46 (62.2%) were from pediatric patients and 28 (37.8%) were from an adult group (P < 0.05), with overall positive values of 49.9% and 41.7%, respectively. All 74 (100%) of the positive samples were isolated in cell culture versus the 68.9% that were detected as positive by the new EIA method (P < 0.05). Of the 41 samples positive for the IA virus, the EIA detected 34 (82.9%) positive samples; of the 33 samples positive for the IB virus, the EIA detected 17 (51.5%) positive samples (P < 0.05). No false-positive reaction was detected with the EIA method (specificity and positive predictive value of 100%). The overall results obtained in the comparison between the new EIA and the shell vial culture had a sensibility of 82.9% and predictive negative values of 92.4% for the IA virus and 51.5% and 84.3%, respectively, for the IB virus. This evaluation shows sensitivity and specificity percentages for the new EIA method that is acceptable for routine use in IA virus detection. The results obtained were worse for IB virus detection, but this new EIA method is actually the only one with the capacity to differentiate between the two influenza viruses.

QuickVue influenza test for rapid detection of influenza A and B viruses in a pediatric population

The performance of a lateral-flow immunoassay, the QuickVue Influenza Test, for detection of influenza A and B viruses in comparison with that of cell culture was evaluated by using nasopharyngeal aspirates, in viral transport medium, from children with respiratory tract infections. The sensitivity and specificity were 79.2 and 82.6%, respectively.

Clinical evaluation of the ZstatFlu-II test: a chemiluminescent rapid diagnostic test for influenza virus

Exploiting the high sensitivity of the chemiluminescence phenomenon, an accurate and sensitive point-of-care test, called the ZstatFlu-II test (ZymeTx, Inc., Oklahoma City, Okla.), was developed to detect influenza virus infections. The ZstatFlu-II test takes 20 min and requires approximately 2 min of "hands-on" time for operational steps. The ZstatFlu-II test does not distinguish between infections with influenza virus types A and B. ZstatFlu-II test results are printed on Polaroid High-Speed Detector Film, allowing test results to be archived. A prototype version of the ZstatFlu-II test was evaluated during the 2000-to-2001 flu season with 300 nasal aspirate specimens from children at a pediatric hospital. Compared to culture, the ZstatFlu-II test had 88% sensitivity and 92% specificity. The Directigen test had a sensitivity of 75% and a specificity of 93%. The sensitivity of the ZstatFlu-II test was significantly higher than that of the Directigen test (P < 0.0574).

[Community-acquired pneumonia associated with influenza virus]

BACKGROUND

Pneumonia is one of the most common complications of influenza infection. However, its characteristics are not well-known. Our aim was to assess the frequency of community-acquired pneumonia (CAP) associated with influenza virus and to determine its clinical and epidemiological characteristics.

PATIENTS AND METHOD

A total of 240 patients with CAP were evaluated and cases with serological evidence of influenza virus infection were identified. Patients in whom there was no evidence of infection by other microbial agents were selected and defined as influenza virus infection-associated CAP (CAP-i). Clinical and epidemiological features of CAP-i patients were compared with the rest of patients with CAP.

RESULTS

A microbial diagnosis was achieved in 143 (59.6%) of 240 patients with CAP. In 12 cases (5%) there was serological evidence of infection by influenza A virus. In 8 patients no other respiratory pathogens were detected (CAP-i). In a multivariate analysis, the presence of arthromyalgias (odds ratio [OR] = 30, 68; 95% confidence interval [CI], 1-946), plasmatic sodium < 133 mEq/l (OR = 16.92; 95% CI, 1.48-193), bilateral infiltrates in chest X-ray (OR = 8.83; 95% CI, 1.35-57.6), diagnosis of CAP in January or February (OR = 5.60; 95% CI, 0.87-35.8) and blood neutrophil cell count >= 14,000/l, (OR = 5.23; 95% CI, 0.85-32) were all independently associated with CAP-i. The simultaneous presence of all these characteristics had a positive and negative predictive value of 95% and 99%, respectively, to differentiate CAP-i from other CAP.

CONCLUSIONS

Influenza virus infection-associated CAP is uncommon. Some clinical and radiographic variables could differentiate CAP-i from other CAP. These parameters could also help identify patients who are more likely to benefit from specific antiviral therapy.

Evaluation of the Directigen FluA+B test for rapid diagnosis of influenza virus type A and B infections

Directigen FluA+B (BD Diagnostic Systems, Sparks, Md.), a new rapid test for the detection of influenza virus types A and B, was evaluated with nasopharyngeal aspirate specimens collected from 250 patients in comparison with culture and direct fluorescent antigen (DFA) detection tests. The patients studied were predominantly children, 80% being </=6 years old. Specimens negative by culture but positive by the Directigen FluA+B or DFA tests were analyzed by reverse transcription-PCR to resolve the discrepant results. The resolved sensitivity, specificity, and positive and negative predictive values of the Directigen FluA+B test for influenza virus type A were 96%, 99.6%, 96%, and 99.6%, respectively, and for influenza virus type B they were 87.5%, 96.8%, 80%, and 98%, respectively. Storage of nasopharyngeal aspirates in virus transport medium at 2 to 8 degrees C for 48 h had little adverse effect on the detection of influenza virus type A, but diagnosis of influenza virus type B is best carried out with fresh specimens. The test detected a range of human and animal influenza virus A subtypes, including the H5N1 and H9N2 viruses that recently caused human disease in Hong Kong.

Laboratory diagnosis of influenza: recent advances

The rapid and accurate diagnosis of influenza virus infection now is available to clinicians practicing in both outpatient and inpatient settings. Newly licensed reagents are reliable and "user friendly" and may impact care by providing an immediate diagnosis that allows appropriate antiviral therapy to be given and encourages judicious use of antibiotics. The diagnosis of influenza by viral culture also has become more mainstream, allowing health professionals to confirm diagnoses in individual patients, as well as to track the pattern of each "flu season" in the community.

Rapid and sensitive detection of respiratory virus infections for directed antiviral treatment using R-Mix cultures

BACKGROUND

The development of new anti-influenza drugs has led to concerns regarding the impact on healthcare costs if they are used indiscriminately. Restricting their use to proven influenza virus infections has the potential to overcome costly inappropriate therapy. However, conventional culture (CC) does not generate results quickly enough to facilitate the timely initiation of treatment, and rapid detection tests have suboptimal sensitivity. We therefore investigated a new rapid culture system (R-Mix) that contains a mixture of two cell lines and detects respiratory viruses within 24 h.

OBJECTIVES

To compare the analytical sensitivity of R-Mix with CC and rapid detection methods, for the detection of influenza and other respiratory viruses. To compare the clinical sensitivity of R-Mix with CC and direct antigen detection for the detection of respiratory viruses in primary and acute care settings.

STUDY DESIGN

Stock cultures of influenza virus were titrated and tested by R-Mix, ZstatFlu and FLU OIA. Stock cultures of adenovirus and parainfluenza virus type 3 were titrated and tested by R-Mix and CC. Specimens, which had previously tested positive for influenza viruses, were titrated and tested by R-Mix and CC. In symptomatic patients, the majority of whom were from primary care settings, 124 sequential specimens were tested for influenza viruses by immunofluorescent direct antigen detection and R-Mix. A separate set of 111 sequential specimens, from various symptomatic patient groups, were tested for influenza viruses by CC and R-Mix. Additionally, in acute care patients being surveillance tested during periods of immunosuppression, 155 specimens were tested for respiratory viruses (influenza A and B, parainfluenza 1-3, adenovirus and respiratory syncytial virus (RSV)) by CC and R-Mix.

RESULTS

With titrated stock cultures, R-Mix showed an analytical limit of detection of ten infectious virus particles per vial for influenza A, compared with 100,000 particles per test for FLU OIA and 1,000,000 for ZstatFlu. R-Mix also showed a 100-fold greater sensitivity for the detection of influenza A and equivalent sensitivity for the detection of influenza B when compared with CC in titrated known positive specimens. Further, it showed equivalent sensitivity to CC for the detection of adenovirus and parainfluenza virus type 3 in titrated stock cultures. Among prospective specimens from symptomatic patients, the sensitivity of R-Mix, CC and direct antigen detection tests (DAT) for influenza virus detection, was 100, 67 and 66%, respectively, and the specificity was 100, 100 and 98%, respectively. In surveillance specimens from immunosuppressed patients, the sensitivities of R-Mix and CC for respiratory virus detection were equivalent. Moreover, R-Mix results were available within 24 h, and by altering the antibody staining reagents either influenza viruses, or all seven major respiratory viruses, could be detected and distinguished in a single test.

CONCLUSIONS

R-Mix is a simple, rapid and sensitive system for the detection of influenza viruses that facilitates the restriction of antiviral drugs to patients with culture-confirmed infections.

Principles of appropriate antibiotic use for treatment of uncomplicated acute bronchitis: background

The following principles of appropriate antibiotic use for adults with acute bronchitis apply to immunocompetent adults without complicating comorbid conditions, such as chronic lung or heart disease.1.

The evaluation of adults with an acute cough illness or a presumptive diagnosis of uncomplicated acute bronchitis should focus on ruling out serious illness, particularly pneumonia. In healthy, nonelderly adults, pneumonia is uncommon in the absence of vital sign abnormalities or asymmetrical lung sounds, and chest radiography is usually not indicated. In patients with cough lasting 3 weeks or longer, chest radiography may be warranted in the absence of other known causes.

2.

Routine antibiotic treatment of uncomplicated acute bronchitis is not recommended, regardless of duration of cough. If pertussis infection is suspected (an unusual circumstance), a diagnostic test should be performed and antimicrobial therapy initiated.

3.

Patient satisfaction with care for acute bronchitis depends most on physician–patient communication rather than on antibiotic treatment.

[Gonzales R, Bartlett JG, Besser RE, Cooper RJ, Hickner JM, Hoffman JR, Sande MA. Principles of appropriate antibiotic use for treatment of uncomplicated acute bronchitis: background. Ann Emerg Med. June 2001;37:720-727.]

Principles of appropriate antibiotic use for treatment of uncomplicated acute bronchitis: background

The following principles of appropriate antibiotic use for adults with acute bronchitis apply to immunocompetent adults without complicating comorbid conditions, such as chronic lung or heart disease. The evaluation of adults with an acute cough illness or a presumptive diagnosis of uncomplicated acute bronchitis should focus on ruling out serious illness, particularly pneumonia. In healthy, nonelderly adults, pneumonia is uncommon in the absence of vital sign abnormalities or asymmetrical lung sounds, and chest radiography is usually not indicated. In patients with cough lasting 3 weeks or longer, chest radiography may be warranted in the absence of other known causes. Routine antibiotic treatment of uncomplicated acute bronchitis is not recommended, regardless of duration of cough. If pertussis infection is suspected (an unusual circumstance), a diagnostic test should be performed and antimicrobial therapy initiated. Patient satisfaction with care for acute bronchitis depends most on physician--patient communication rather than on antibiotic treatment.

Evaluation of the Hexaplex assay for detection of respiratory viruses in children

The Hexaplex assay (Prodesse, Inc., Milwaukee, Wis.) is a multiplex reverse transcriptase (RT)-PCR assay for the detection of parainfluenza virus types 1, 2, and 3, respiratory syncytial virus (RSV) types A and B, and influenza virus types A and B. We evaluated the Hexaplex assay in comparison with conventional viral cell cultures and rapid enzyme immunoassays (EIAs) for RSV (Directigen; Becton Dickinson Inc., Cockeysville, Md.) and influenza A virus (Abbott Test Pack; Abbott Laboratories, Abbott Park, Ill.) for the detection of respiratory viruses from pediatric respiratory specimens obtained from children seen at Children's Hospital of Wisconsin from December 1997 through May 1998. A total of 363 respiratory specimens were evaluated. The tissue culture prevalence of parainfluenza virus during this period of time was low (1.1%). The sensitivity, specificity, and positive and negative predictive value of Hexaplex compared to tissue culture for the detection of parainfluenza virus were 100, 95.8, 19.0, and 100%, respectively. Only one specimen was determined to contain influenza B virus by Hexaplex; it was tissue culture negative. A specimen was considered to contain RSV or influenza A virus when it was either culture positive or culture negative but Hexaplex and EIA positive. Prior to the analysis of discrepant results, the sensitivity, specificity, and positive and negative predictive value for the detection of RSV were 91.2, 100, 100, and 98.0%, respectively, for tissue culture; 84.5, 100, 100, and 96.6% for EIA; and 98.5, 91.5, 72.8, and 99.6% for Hexaplex, respectively. The sensitivity, specificity, and positive and negative predictive value for the detection of influenza A virus prior to the analysis of discrepant results were 100, 100, 100, and 100%, respectively, for culture, 78.0, 100, 100, and 89.4% for EIA, respectively, and 95.1, 94.1, 67.2, and 99.3% for Hexaplex, respectively. Culture- and/or EIA-negative, Hexaplex-positive specimens were analyzed by a second RT-PCR assay which used primers specific for a different genomic region than that used in the Hexaplex assay. After analysis of these discrepant results, the sensitivity, specificity, and positive and negative predictive value for the detection of RSV were 74.3, 100, 100, and 93.5%, respectively, for tissue culture; 70.3, 100, 100, and 92.5% for EIA; and 98.6, 97.4, 91.2, and 99.6% for Hexaplex. The sensitivity, specificity, and positive and negative predictive value for the detection of influenza A virus were 83.3, 100, 100, and 97.4%, respectively, for tissue culture; 69.4, 100, 100, and 83.3% for EIA; and 95.8, 98.7, 92.0, and 99.3% for Hexaplex. Hexaplex is a rapid, sensitive, and specific method for the detection of the seven most common respiratory viruses in children.

Comparative enzymology, biochemistry and pathophysiology of human exo-alpha-sialidases (neuraminidases)

This review summarizes the current research on human exo-alpha-sialidase (sialidase, neuraminidase). Where appropriate, the properties of viral, bacterial, and human sialidases have been compared. Sialic acids are implicated in diverse physiological processes. Sialidases, as enzymes acting upon sialic acids, assume importance as well. Sialidases hydrolyze the terminal, non-reducing, sialic acid linkage in glycoproteins, glycolipids, gangliosides, polysaccharides, and synthetic molecules. Therefore, a variety of assays are available to measure sialidase activity. Human sialidase is present in several organs and cells. Its cellular distribution could be cytosolic, lysosomal, or in the membrane. Human sialidase occurs in a high molecular-mass complex with several other proteins, including cathepsin A and beta-galactosidase. Multi-protein complexation is important for the in vivo integrity and catalytic activity of the sialidase. However, multi-protein complexation, the occurrence of isoenzymes, diverse subcellular localization, thermal instability, and membrane association have all contributed to difficulties in purifying and characterizing human sialidases. Human sialidase isoenzymes have recently been cloned and sequenced. Even though crystal structures for the human sialidases are not available, the highly conserved regions of the sialidase from various organisms have facilitated molecular modeling of the human enzyme and raise interesting evolutionary questions. While the molecular mechanisms vary, genetic defects leading to human sialidase deficiency are closely associated with at least two well-known human diseases, namely sialidosis and galactosialidosis. No therapy is currently available for either disease. A thorough investigation of human sialidases is therefore crucial to human health.

Update on influenza and other viral pneumonias

Major developments during the past 5 years concerning influenza prevention by vaccination and treatment with neuraminidase inhibitors are reviewed. These have been accompanied by increased media interest in related issues: pressures on hospital admissions, ethical concerns and controls on prescribing limiting professional autonomy. The new live attenuated influenza vaccines, adjuvanted vaccines and the emerging recombinant DNA vaccines are discussed. Recent information on neuraminidase inhibitor antivirals, surveillance for resistant viruses, the prospects for near patient tests (i.e. tests that can be used near the patient to improve immediate patient management or in the laboratory to give rapid feedback for physicians) and the clinical significance of other respiratory viruses are highlighted. The benefits of recent advances provide challenges for health care delivery and public acceptance as great as those involved in their scientific development.

Evaluation of a rapid optical immunoassay for influenza viruses (FLU OIA test) in comparison with cell culture and reverse transcription-PCR

The FLU OIA test was evaluated with 146 throat swab specimens from subjects with a flu-like illness in six Canadian clinics during the 1999-2000 flu season. The rate of positivity of the FLU OIA test (41.5%) was significantly lower than that of cell culture (55.2%) or reverse transcription-PCR (55.9%) during a season in which only influenza A virus was detected.