Comparison of rapid detection methods for influenza A virus and their value in health-care management of institutionalized geriatric patients

Pathology Consultation on Influenza Diagnostics

OBJECTIVES

To describe the strengths and limitations of the available influenza diagnostics, with a focus on rapid antigen detection assays and nucleic acid detection assays.

METHODS

A case-based presentation is used to illustrate the potential limitations of rapid antigen detection assays for influenza.

RESULTS

Influenza is a seasonal illness; estimates attribute influenza to approximately 200,000 hospitalizations and 41,000 deaths in the United States annually. Antigen detection assays for influenza are rapid and convenient, and thus are widely used in a variety of health care settings, even though the sensitivity of these assays may be suboptimal. The United States Food and Drug Administration has recently created new guidelines intended to improve the oversight and performance characteristics of influenza antigen detection assays. Molecular assays, although more costly and complex, are more sensitive and may be designed to simultaneously detect multiple respiratory pathogens within a single assay.

CONCLUSIONS

Diagnostic assays for influenza can vary greatly with regards to analytical performance characteristics, complexity, turnaround time and cost. This can have important patient care and infection prevention implications.

Detection of respiratory viruses in sputum from adults by use of automated multiplex PCR

Respiratory tract infections (RTI) frequently cause hospital admissions among adults. Diagnostic viral reverse transcriptase PCR (RT-PCR) of nose and throat swabs (NTS) is useful for patient care by informing antiviral use and appropriate isolation. However, automated RT-PCR systems are not amenable to utilizing sputum due to its viscosity. We evaluated a simple method of processing sputum samples in a fully automated respiratory viral panel RT-PCR assay (FilmArray). Archived sputum and NTS samples collected in 2008-2012 from hospitalized adults with RTI were evaluated. A subset of sputum samples positive for 10 common viruses by a uniplex RT-PCR was selected. A sterile cotton-tip swab was dunked in sputum, swirled in 700 μL of sterile water (dunk and swirl method) and tested by the FilmArray assay. Quantitative RT-PCR was performed on "dunked" sputum and NTS samples for influenza A (Flu A), respiratory syncytial virus (RSV), coronavirus OC43 (OC43), and human metapneumovirus (HMPV). Viruses were identified in 31% of 965 illnesses using a uniplex RT-PCR. The sputum sample was the only sample positive for 105 subjects, including 35% (22/64) of influenza cases and significantly increased the diagnostic yield of NTS alone (302/965 [31%] versus 197/965 [20%]; P = 0.0001). Of 108 sputum samples evaluated by the FilmArray assay using the dunk and swirl method, 99 (92%) were positive. Quantitative RT-PCR revealed higher mean viral loads in dunked sputum samples compared to NTS samples for Flu A, RSV, and HMPV (P = 0.0001, P = 0.006, and P = 0.011, respectively). The dunk and swirl method is a simple and practical method for reliably processing sputum samples in a fully automated PCR system. The higher viral loads in sputa may increase detection over NTS testing alone.

Evolving gene targets and technology in influenza detection

Influenza viruses cause recurring epidemic outbreaks every year associated with high morbidity and mortality. Despite extensive research and surveillance efforts to control influenza outbreaks, the primary mitigation treatment for influenza is the development of yearly vaccine mixes targeted for the most prevalent virus strains. Consequently, the focus of many detection technologies has evolved toward accurate identification of subtype and understanding the evolution and molecular determinants of novel and pathogenic forms of influenza. The recent availability of potential antiviral treatments are only effective if rapid and accurate diagnostic tests for influenza epidemic management are available; thus, early detection of influenza infection is still important for prevention, containment, patient management, and infection control. This review discusses the current and emerging technologies for detection and strain identification of influenza virus and their specific gene targets, as well as their implications in patient management.

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.

Strengths and weaknesses of FDA-approved/cleared diagnostic devices for the molecular detection of respiratory pathogens

The rapid, sensitive, and specific identification of the microbial etiological characteristics of respiratory tract infections enhances the appropriate use of both antibiotics and antiviral agents and reduces the risk of nosocomial transmission. This article reviews the current nucleic acid amplification tests approved by the U.S. Food and Drug Administration (FDA) for the detection of respiratory pathogens. In addition, Emergency Use Authorization tests for the detection of 2009 influenza A H1N1 are discussed. The advantages and limitations of the current FDA-approved/cleared tests are reviewed.

Multiplexed, rapid detection of H5N1 using a PCR-free nanoparticle-based genomic microarray assay

BACKGROUND

For more than a decade there has been increasing interest in the use of nanotechnology and microarray platforms for diagnostic applications. In this report, we describe a rapid and simple gold nanoparticle (NP)-based genomic microarray assay for specific identification of avian influenza virus H5N1 and its discrimination from other major influenza A virus strains (H1N1, H3N2).

RESULTS

Capture and intermediate oligonucleotides were designed based on the consensus sequences of the matrix (M) gene of H1N1, H3N2 and H5N1 viruses, and sequences specific for the hemaglutinin (HA) and neuraminidase (NA) genes of the H5N1 virus. Viral RNA was detected within 2.5 hours using capture-target-intermediate oligonucleotide hybridization and gold NP-mediated silver staining in the absence of RNA fragmentation, target amplification, and enzymatic reactions. The lower limit of detection (LOD) of the assay was less than 100 fM for purified PCR fragments and 103 TCID50 units for H5N1 viral RNA.

CONCLUSIONS

The NP-based microarray assay was able to detect and distinguish H5N1 sequences from those of major influenza A viruses (H1N1, H3N2). The new method described here may be useful for simultaneous detection and subtyping of major influenza A viruses.

Evaluation of a rapid diagnostic test, NanoSign® Influenza A/B Antigen, for detection of the 2009 pandemic influenza A/H1N1 viruses

Background

This study evaluated the clinical accuracy and analytical sensitivity of the NanoSign^® Influenza A/B antigen kit in detecting 2009 pandemic influenza A/H1N1 viruses. The kit is one of the most popular rapid diagnostic tests for detecting influenza in Republic of Korea.

Results

The NanoSign^® Influenza A/B kit resulted in 79.4% sensitivity and 97.2% specificity compared to RT-PCR in the detection of the viruses from 1,023 specimens. In addition, the kit was able to detect two strains of novel influenza viruses, Influenza A/California/12/2009(H1N1) and clinically isolated wild-type novel influenza A/H1N1, both of which are spreading epidemically throughout the world. In addition, the correlation between NanoSign^® Influenza A/B test and conventional RT-PCR was approximately 94%, indicating a high concordance rate. Analytical sensitivity of the kit was approximately 73 ± 3.65 ng/mL of the purified viral proteins and 1.13 ± 0.11 hemagglutination units for the cultured virus.

Conclusions

As the NanoSign^® Influenza A/B kit showed relatively high sensitivity and specificity and the good correlation with RT-PCR, it will be very useful in the early control of influenza infection and in helping physicians in making early treatment decisions.

[Seasonal flu]

La grippe saisonnière est due aux virus influenza A et B. Il s’agit de virus enveloppés dont le génome est constitué de sept à huit fragments d’ARN. Les différents sous-types sont déterminés par la nature des deux glycoprotéines de surface HA et NA. La grippe saisonnière est une maladie épidémique et hivernale dans les zones à climat tempéré. Son épidémiologie est liée à la grande variabilité du virus au cours du temps, nécessitant la mise en place d’un système d’alerte détectant chaque année les variants circulants dominant et déterminant la composition vaccinale. Les symptômes cliniques de la grippe ne sont pas suffisamment spécifiques pour permettre le diagnostic sans examen virologique. Cela est particulièrement vrai en période non épidémique, chez les sujets de plus de 65 ans et chez les enfants de moins de cinq ans. L’enfant représente une cible privilégiée des infections à virus influenza. Le recours à l’hospitalisation est d’autant plus élevé que l’enfant est jeune. Chez le nourrisson, l’infection peut être paucisymptomatique et s’accompagner de manifestations non respiratoires (léthargie, convulsions, malaises). Le diagnostic virologique de la grippe est justifié chez tous les sujets hospitalisés pour un syndrome respiratoire compatible avec une infection à virus influenza. Il existe plusieurs outils permettant une recherche directe du virus dans les sécrétions respiratoires : isolement du virus en culture, détection d’antigènes, détection moléculaire de l’ARN. Le choix de la méthode se fait selon les caractéristiques du test : sensibilité, spécificité, rapidité et simplicité de réalisation, coût.

Public hospital-based laboratory experience during an outbreak of pandemic influenza A (H1N1) virus infections

The experience of a public hospital virology laboratory during a springtime 2009 outbreak of a novel influenza A (H1N1) virus in New York State is described. Influenza virus was isolated from 145 of 613 respiratory swab specimens. Symptoms of fever (temperature, 102.7 +/- 0.32 degrees F), cough, upper respiratory infection, myalgia, and headache were reported. Atypical symptoms of nausea/vomiting and diarrhea were also observed. Illness occurred mainly in patients <or=21 years of age (85/145 patients). Only two patients were >or=65 years old. Compared to the results of traditional culture methods, the sensitivities of a rapid chromatographic influenza A and B virus immunoassay and rapid shell vial culture were 70.3% and 98.6%, respectively. A sensitivity of 80% was obtained by testing 50 specimens by a direct fluorescent-antibody (DFA) assay. The observation of adequate numbers of cells on the DFA assay slides suggests that the low sensitivity of the chromatographic immunoassay may result from its intrinsic nature and not from improper specimen collection. A reverse transcription-PCR (RT-PCR) assay of 45 specimens performed off-site yielded 21 novel (H1N1) viruses and 2 seasonal (H3N2) influenza viruses. The mean time interval of 5.69 +/- 0.37 days from specimen collection to the availability of RT-PCR results limited the value of this assay for patient care. In laboratories lacking on-site molecular capabilities, shell vial techniques can rapidly (about 1 day) confirm negative results and/or identify false-negative chromatographic immunoassay results. Laboratories lacking culture capabilities may also use the DFA assay to confirm or replace the results obtained by these immunoassays. Increasing testing demands caused shortages in commodities and personnel. Alternative testing strategies and planning are necessary in order to optimize virus detection and ensure appropriate resource allocation.

Outcome of critically ill patients with influenza virus infection

Background

Influenza is a major cause of morbidity and mortality, with its greatest burden on the elderly and patients with chronic co-morbidities in the intensive care unit (ICU). An accurate prognosis is essential for decision-making during pandemic as well as interpandemic periods.

Methods

A retrospective cohort study was conducted to determine prognostic factors influencing short term outcome of critically ill patients with confirmed influenza virus infection. Baseline characteristics, laboratory and diagnostic findings, ICU interventions and complications were abstracted from medical records using standard definitions and compared between hospital survivors and non-survivors with univariate and multivariate logistic regression analyses.

Results

111 patients met the inclusion criteria. Acute respiratory distress syndrome (ARDS) complicated ICU course in 25 (23%) of the patients, with mortality rate of 52%. Multivariate logistic regression analysis identified the following predictors of hospital mortality: Acute Physiology and Chronic Health Evaluation (APACHE) III predicted mortality (Odds ratio [OR] 1.49, 95% confidence interval [CI] 1.1–2.1 for 10% increase), ARDS (OR 7.7, 95% CI 2.3–29) and history of immunosuppression (OR 7.19, 95% CI 1.9–28).

Conclusions

APACHE III predicted mortality, the development of ARDS and the history of immunosuppression are independent risk factors for hospital mortality in critically ill patients with confirmed influenza virus infection.

Development of a multiplex real-time polymerase chain reaction for the detection of influenza virus type A including H5 and H9 subtypes

Avian influenza viruses (AIVs) are endemic in wild birds and, if transmitted to poultry, can cause serious economic losses. The aim of this study was to develop a multiplex real-time reverse transcriptase polymerase chain reaction (RT-PCR) for rapid detection of influenza virus type A, including H5 and H9 subtypes. The selected primers and various labeled TaqMan reporter probes corresponding to matrix, H5, and H9 genes were used in a multiplex real-time RT-PCR to simultaneously detect triple fluorescent signals. The results showed that the multiplex real-time RT-PCR assay can be applied to detect RNA of influenza virus type A including H5 and H9 subtypes with a high specificity and a sensitivity of 10 copies per reaction. As a result of its short turnaround times and a high specificity and sensitivity, the assay is very suitable for large-scale screening during AIV outbreaks.

Comparison of the MChip to viral culture, reverse transcription-PCR, and the QuickVue influenza A+B test for rapid diagnosis of influenza

The performance of a diagnostic microarray (the MChip assay) for influenza was compared in a blind study to that of viral culture, reverse transcription (RT)-PCR, and the QuickVue Influenza A+B test. The patient sample data set was composed of 102 respiratory secretion specimens collected between 29 December 2005 and 2 February 2006 at Scott & White Hospital and Clinic in Temple, Texas. Samples were collected from a wide range of age groups by using direct collection, nasal/nasopharyngeal swabs, or nasopharyngeal aspiration. Viral culture and the QuickVue assay were performed at the Texas site at the time of collection. Aliquots for each sample, identified only by study numbers, were provided to the University of Colorado and Vanderbilt University teams for blinded analysis. When referenced to viral culture, the MChip exhibited a clinical sensitivity of 98% and a clinical specificity of 98%. When referenced to RT-PCR, the MChip assay exhibited a clinical sensitivity of 92% and a clinical specificity of 98%. While the MChip assay currently requires 7 to 8 h to complete the analysis, a significant advantage of the test for influenza virus-positive samples is simultaneous detection and full subtype identification for the two subtypes currently circulating in humans (A/H3N2 and A/H1N1) and avian (A/H5N1) viruses.

Experimental evaluation of the FluChip diagnostic microarray for influenza virus surveillance

Global surveillance of influenza is critical for improvements in disease management and is especially important for early detection, rapid intervention, and a possible reduction of the impact of an influenza pandemic. Enhanced surveillance requires rapid, robust, and inexpensive analytical techniques capable of providing a detailed analysis of influenza virus strains. Low-density oligonucleotide microarrays with highly multiplexed "signatures" for influenza viruses offer many of the desired characteristics. However, the high mutability of the influenza virus represents a design challenge. In order for an influenza virus microarray to be of utility, it must provide information for a wide range of viral strains and lineages. The design and characterization of an influenza microarray, the FluChip-55 microarray, for the relatively rapid identification of influenza A virus subtypes H1N1, H3N2, and H5N1 are described here. In this work, a small set of sequences was carefully selected to exhibit broad coverage for the influenza A and B viruses currently circulating in the human population as well as the avian A/H5N1 virus that has become enzootic in poultry in Southeast Asia and that has recently spread to Europe. A complete assay involving extraction and amplification of the viral RNA was developed and tested. In a blind study of 72 influenza virus isolates, RNA from a wide range of influenza A and B viruses was amplified, hybridized, labeled with a fluorophore, and imaged. The entire analysis time was less than 12 h. The combined results for two assays provided the absolutely correct types and subtypes for an average of 72% of the isolates, the correct type and partially correct subtype information for 13% of the isolates, the correct type only for 10% of the isolates, false-negative signals for 4% of the isolates, and false-positive signals for 1% of the isolates. In the overwhelming majority of cases in which incomplete subtyping was observed, the failure was due to the nucleic acid amplification step rather than limitations in the microarray.

Experience With the Rapid Directigen Test for Influenza

OBJECTIVE

To determine the sensitivity and positive predictive value of the Becton-Dickson Directigen AB performed on-site in a nursing home compared to viral culture.

SETTING

A 721-bed skilled nursing facility for veterans and spouses. DESIGN MEASUREMENTS: Nasopharyngeal specimens were obtained with a low clinical threshold from residents during 3 influenza seasons for rapid antigen testing in the nursing home. The specimens were then transported for viral culture by courier on ice to a laboratory 45 miles away.

RESULTS

A total of 327 samples were obtained; 36 were positive for influenza A by rapid test, and all but 2 grew the organism on tissue culture with a positive predictive value of 94%. Nineteen specimens were negative by rapid test, but grew influenza A on tissue culture with a sensitivity of 64%. Influenza prophylaxis was usually initiated the day the first positive rapid test was encountered when influenza was active in the community.

CONCLUSION

The Directigen AB is a reliable indicator of influenza when influenza has been culture-confirmed in the community. Although sensitivity is limited, a group of rapid tests provided early laboratory confirmation and facilitated the application of prophylaxis.

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.

A 5-year experience with influenza prevention and containment in a program of all-inclusive care for elderly adults

BACKGROUND

Influenza causes mortality and morbidity in the frail elderly population. Influenza prevention and mitigation models need to be developed for this population.

METHODS

An observational study at a Program for All-Inclusive Care for the Elderly (PACE) during years 1999-2004. Participants were frail elderly adults who meet the state Medicaid requirements for nursing home placement.

RESULTS

Over 91% of participants have been immunized yearly since the beginning of the program. Employee immunization has increased yearly from 61% to 90%, and caregivers known to be immunized increased from 9% to 62% over the last 4-year period. During 2 influenza seasons, we placed all our participants on ramantidine prophylaxis within a 2-week period.

CONCLUSIONS

The incentives and flexibility offered by PACE have allowed our participants to enjoy much higher influenza immunization rates than experienced by other elderly adults while also prophylaxing employees and caregivers. Our systems have allowed us to prophylax all our participants within a short time during 2 influenza seasons. Nonetheless, many questions remain regarding the optimal way to decrease the burden of influenza in frail elderly adults. With adequate integration and supplementary financing, PACE programs throughout the United States could serve as laboratories to test candidate interventions.

Viral diagnosis by antigen detection techniques

BACKGROUND

Diagnosis of viral infections can be obtained in the early stages of a disease by detection of viral antigens directly in the clinical specimen. This has become an important tool for rapid virus diagnosis.

METHODS

Antigens produced during virus infections can be detected either in cells collected from the site of infection by immunohistological investigation or in secretions and blood by solid phase immunoassays (IA). Viruses causing acute respiratory infections can be diagnosed in cells from the respiratory tract, viruses causing vesicular eruptions in epithelial cells from skin scrapings, rabies virus in nerve cells of the brain or epithelial cells from skin and cornea and cytomegalovirus (CMV) matrix antigen, pp65, can be detected in peripheral blood leukocytes (PBL) by immunofluorescence (IF) or immunoperoxidase techniques. The quality of specimens can be easily checked during the reading of results. Some IAs for antigen detection, such as detection of HBsAg and HIV p24 antigen in blood are standardized and sensitive. Others give less sensitive results because of the variation of quality of the clinical specimen. The latex agglutination tests are mainly used for rapid detection of virus or viral antigens in faeces: rota-and adenoviruses; the method may not be very sensitive but yields a result within a few minutes. Assays detecting viral nucleic acids are more sensitive than antigen detection tests because of a tremendous amplification of gene segments obtained by the polymerase chain reaction (PCR). So far such assays are time consuming and expensive and are mainly used in specific clinical situations.

RESULTS

After introduction of specific monoclonal antibodies (Mabs), the antigen detection techniques are increasingly used. the need for quality control, trained staff, and standardized reagents and methods for specimen collection and preparation is now being appreciated. IF for viral respiratory viruses is used for diagnosis and epidemiological studies all over the world. Likewise, IF is still the method most often used for rabies diagnosis. For CMV, the pp65 matrix antigen is shown to be a sensitive marker closely correlated with clinical symptoms. Its detection by the IF technique has proven to be superior to other techniques for prediction of CMV pneumonia in bone marrow transplant patients. IAs are currently used in fully automated systems for large scale diagnosis based on antigen detection in serum specimens. Increase of antibody specificity on the solid phase by use of Mabs directed against the most abundant viral antigen in the clinical specimen shortens the reaction time; this has been employed in most of the constantly appearing new rapid diagnosis kits based on the immunoassay principle.

CONCLUSION

Although, in virology, more sensitive results are obtained by the gene detection method, PCR, directly in clinical samples, viral antigen detection tests are, after the introduction of Mabs for diagnostic purposes, increasingly used because of their low demand on laboratory equipment, their rapid and early result and relatively low cost. Antigen detection is successfully used directly in clinical specimens for rapid diagnosis of many viral infections as well as for identification of tissue culture isolated viruses. With Mab-based IAs the reaction time is shortened and new rapid, almost 'instant test' kits are appearing on the market.

Influenza in the intensive care unit

Influenza remains an important epidemic viral infection. Thousands of deaths occur and billions of dollars are spent each year with influenza-related illnesses. Morbidity and mortality are largely attributed to respiratory complications that may require intensive care unit (ICU) admission. Medical and neonatal ICUs, transplant units, chronic-care wards, and nursing homes are at increased risk for nosocomial outbreaks of influenza, which are characterized by abrupt onset and rapid spread. In this article, the authors review the current concepts, recent advances, and management strategies in influenza-associated pneumonia. Pertinent issues to the critical care practitioner are discussed in detail.

Detection of influenza antigen with rapid antibody-based tests after intranasal influenza vaccination (FluMist)

Rapid tests for influenza antigen detection are frequently used, but it is not known how receipt of intranasal influenza vaccine affects results of these tests. We tested healthy adults who received either intranasal or intramuscular influenza vaccine. Of the 14 intranasal vaccine recipients, 7 (50%) had a direct fluorescent antibody test (DFA) result and 2 (14%) had an enzyme immunoassay (EIA) result that was positive for influenza antigen within 7 days after vaccination. No subjects had positive EIA results on day 12 or 13 after vaccination. For some intranasal vaccine recipients, rapid influenza-antigen detection tests yield positive results within 1 week after vaccination.

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.

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.

Antivirals for influenza: what is their role in the older patient?

Influenza infection is a cause of high morbidity and mortality in the elderly living in the community or in long-term care facilities. Yearly immunisation is the most important means for prevention of infection. However, protection by vaccination in the elderly is incomplete, and influenza infections and outbreaks in long-term care facilities still occur. Symptoms of influenza include fever, chills, headache, myalgia and respiratory symptoms. These clinical features overlap considerably with other co-circulating respiratory viruses such as respiratory syncytial virus and parainfluenza virus. Elderly and debilitated patients with influenza may present with less prominent respiratory symptoms and may present only with fever, lassitude and confusion. Antiviral prophylaxis and treatment with amantadine and rimantadine have been given in the past but adverse effects and early development of drug resistance have limited their use. The newer antivirals zanamivir and oseltamivir are equally effective and have the advantage of being well tolerated and active against both influenza A and B without the development of resistance. However, they are costly. Early identification and diagnosis of influenza illnesses are crucial since treatment with antiviral agents should be started within 48 hours of the beginning of illness.

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.

Practical and sensitive screening strategy for detection of influenza virus

This study evaluated the performance of Directigen FluA combined with a 3-day flu screening culture for the detection of influenza virus. This abbreviated protocol was a useful and effective tool and resulted in a substantial reduction in time, effort, and money spent, while not compromising sensitivity of influenza virus detection.

Clinical features of influenza A virus infection in older hospitalized persons

OBJECTIVES

To determine the value of clinical parameters in predicting influenza in older persons and those with underlying cardiopulmonary conditions hospitalized with respiratory illnesses.

DESIGN

Prospective evaluation of hospitalized persons from November 15, 1999, to April 15, 2000.

SETTING

A 450-bed general medical-surgical hospital in Rochester, New York.

PARTICIPANTS

Patients aged 65 and older or those with underlying cardiopulmonary conditions admitted to the hospital with respiratory diagnoses.

MEASUREMENTS

The ability to discriminate influenza from noninfluenza cases using clinical parameters. Influenza infection was documented by culture, rapid antigen detection, reverse transcription-polymerase chain reaction, or serology.

RESULTS

Sixty-one influenza A infections (mean age +/- standard deviation = 79 +/- 10) were identified in 332 evaluated illnesses (18.3%). Fifty-six cases occurred in 168 patients (33%) during a 9-week epidemic period; 40 were considered contagious on the basis of a positive culture or antigen test. Neither single clinical parameters nor logistic regression analysis using all parameters clearly discriminated influenza from noninfluenza cases. The complex of cough, temperature of 38 degrees C or higher, and illness duration of 7 days or less provided the best discrimination between infected and uninfected subjects; during the epidemic period, 53% of subjects with this symptom complex had influenza, compared with 18% without these symptoms (relative risk = 2.99, 95% confidence interval = 1.85-4.83). This symptom complex had a sensitivity of 78% and a specificity of 73% for contagious influenza during the epidemic period.

CONCLUSIONS

In older persons and those with underlying cardiopulmonary conditions admitted with acute respiratory illness during influenza epidemics, the presence of fever, cough, and brief illness should be useful for institution of respiratory isolation and for design of antiviral trials.

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.

Clinical and economic evaluation of rapid influenza a virus testing in nursing homes in calgary, Canada

The incremental benefits and costs of a rapid influenza A virus infection diagnostic service were studied in nursing homes in Calgary, Canada, during a single influenza season. The service was used to test 159 patients with suspected infection in a group of "experimental" nursing homes and results were compared with those for a group of "control" homes. An equal number of cases of influenza were identified in each group. Twenty-eight patients (17.6%) had confirmed cases, and 63 patients (39.6%) had probable cases. A rapid viral test result was provided much faster for patients in the experimental homes (P=.005). Both groups had the same median attack rate for influenza A virus. In experimental homes, the duration of the outbreak was shorter (P=.03), and the cost of laboratory testing and the total cost (less the hospital cost) tended to be lower (P<.2). The rapid testing service also tended to lower the overall use of resources.

Influenza in the acute hospital setting

Influenza poses special hazards inside healthcare facilities and can cause explosive outbreaks of illness. Healthcare workers are at risk of acquiring influenza and thus serve as an important reservoir for patients under their care. Annual influenza immunisation of high-risk persons and their contacts, including healthcare workers, is the primary means of preventing nosocomial influenza. Despite influenza vaccine effectiveness, it is substantially underused by healthcare providers. Influenza can be diagnosed by culturing the virus from respiratory secretions and by rapid antigen detection kits; recognition of a nosocomial outbreak is important in order to employ infection-control efforts. Optimal control of influenza in the acute-care setting should focus upon reducing potential influenza reservoirs in the hospital, including: isolating patients with suspected or documented influenza, sending home healthcare providers or staff who exhibit typical symptoms of influenza, and discouraging persons with febrile respiratory illness from visiting the hospital during a known influenza outbreak in the community. (Note: influenza and other respiratory viruses can cause non-febrile illness but are still transmissible.) The antiviral M2 protein inhibitors (amantadine, rimantadine) and neuraminidase inhibitors (zanamivir, oseltamivir) have proven efficacy in treating and preventing influenza illness; however, their role in the prevention and control of influenza in the acute hospital setting remains to be more fully studied.

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.

Enhancing public health surveillance for influenza virus by incorporating newly available rapid diagnostic tests

Beginning with the 1999-2000 influenza season, physicians throughout Hawaii ordering a viral culture for patients with suspected influenza were also offered influenza rapid testing. We compared the number of viral respiratory cultures sent to the Hawaii Department of Health and the number of providers who participated in influenza surveillance over consecutive influenza seasons. The number of viral respiratory cultures rose from 396 to 2,169 between the 1998-1999 and 2000-2001 influenza seasons, and the number of providers submitting >1 influenza culture increased from 34 to 327, respectively. The number of influenza isolates obtained each season also increased (from 64 to 491). The available data suggest that the changes observed in Hawaii's influenza surveillance were not secondary to differences in influenza activity between seasons. This is the first evaluation of integrating influenza rapid testing into public health surveillance. Coupling rapid tests with cultures appears to be an effective means of improving influenza surveillance.

The mercury concentration in saliva: correlation to number and extension of dental amalgam restorations

Beginning with the 1999-2000 influenza season, physicians throughout Hawaii ordering a viral culture for patients with suspected influenza were also offered influenza rapid testing. We compared the number of viral respiratory cultures sent to the Hawaii Department of Health and the number of providers who participated in influenza surveillance over consecutive influenza seasons. The number of viral respiratory cultures rose from 396 to 2,169 between the 1998-1999 and 2000-2001 influenza seasons, and the number of providers submitting >1 influenza culture increased from 34 to 327, respectively. The number of influenza isolates obtained each season also increased (from 64 to 491). The available data suggest that the changes observed in Hawaii’s influenza surveillance were not secondary to differences in influenza activity between seasons. This is the first evaluation of integrating influenza rapid testing into public health surveillance. Coupling rapid tests with cultures appears to be an effective means of improving influenza surveillance.

The role of the laboratory in infection prevention and control programs in long-term-care facilities for the elderly

Hospital infection prevention and control programs rely extensively on diagnostic microbiology laboratory testing. However, specimens for microbiological evaluation are less likely to be obtained from elderly residents of long-term-care facilities (LTCFs). In this article, issues regarding laboratory utilization and the potential role of the microbiology laboratory in infection prevention and control programs in LTCFs are reviewed. The role of the laboratory in infection surveillance, in the management of antimicrobial resistance, and in outbreak investigation are highlighted.

Influenza pneumonia: a descriptive study

OBJECTIVE

To describe the clinical features and complications of patients hospitalized with influenza during the 1999-2000 influenza season.

METHODS

We reviewed all cases of patients with influenza admitted to a large metropolitan referral hospital during the 1999-2000 season.

RESULTS

Thirty-five adult patients (15 men and 20 women) tested positive for influenza A by direct enzyme immunoassay. A fourfold to sevenfold increase in the number of influenza cases was observed over previous years. Most patients had serious comorbid illnesses (88%), such as diabetes and chronic respiratory and heart disease. Seventeen patients developed pneumonia; these patients tended to be older (mean +/- SD, 63 +/- 13 years vs 51 +/- 19 years, respectively; p = 0.04) and had a higher incidence of chronic lung disease (41% vs 6%, respectively; p = 0.02) than the patients without pneumonia. Shortness of breath was the only symptom that distinguished patients with pneumonia from those with an upper respiratory tract illness alone. Antiviral treatment was begun 4 +/- 3 days from initiation of symptoms in patients with pneumonia and consisted of oseltamivir (35.2%), rimantadine (5.8%), or a combination of both (17.6%). Respiratory and/or blood culture results were positive in five patients (29%), Staphylococcus aureus was isolated in five patients, and Streptococcus pneumoniae was isolated in one patient. Ten of the patients with pneumonia (58.8%) were admitted to the ICU, and 5 patients (29%) died. The length of ICU stay and mechanical ventilation were 28 +/- 26 days and 21.5 +/- 20.5 days, respectively. Death in most pneumonia patients was attributed to respiratory failure.

CONCLUSION

The recognized number of hospital admissions for influenza increased fourfold to sevenfold over previous years, most likely due to the implementation of rapid diagnostic tests for influenza. Patients with signs and symptoms of influenza and shortness of breath should undergo chest radiography. Hospitalization of patients with influenza pneumonia occurred in both previously healthy and immunocompromised patients and had a high mortality. S aureus was the most common bacterial isolate in patients with influenza pneumonia. Empiric antibiotics with staphylococcal activity should be used pending culture results in patients with influenza pneumonia. The effectiveness of oseltamivir and rimantadine in treating patients with influenza pneumonia remains to be determined.

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.

Approach to the problem of pneumonia in long-term care facilities

The incidence of pneumonia among patients in long-term care facilities is approximately 1/1000 patient-days. Evidence indicates that the majority can be managed without transfer to a hospital. Immunization with pneumococcal and influenza vaccines is appropriate for all residents.

Practice guideline for evaluation of fever and infection in long-term care facilities

The elderly population (i.e., persons aged > or = 65 years) in the United States is rapidly expanding and will nearly double in number over the next 30 years. It is estimated that >40% of persons aged > or = 65 years will require care in a long-term care facility (LTCF), such as a skilled nursing facility (SNF), at some point during their lifetime. For the most part, residents of LTCFs are very old and have age-related immunologic changes, chronic cognitive and/or physical impairments, and diseases that alter host resistance; therefore, they are highly susceptible to infections and their complications. The diagnosis of infections in residents of LTCFs is often difficult because LTCFs differ from acute-care facilities in their goals of care, staffing ratios, types of primary care providers, availability of laboratory tests, and criteria for infections. Consequently, guidelines and standards of practice used for diagnosis of infections in patients in acute-care facilities may not be applicable nor appropriate for residents in LTCFs. Moreover, the clinical manifestations of diseases and infections are often subtle, atypical, or nonexistent in the very old. Fever may be low or absent in LTCF residents with infection. The initial evaluation of an LTCF resident suspected of an infection may not be done by a physician. Although nurses commonly perform initial assessments for infection in residents of LTCFs, further studies are needed to determine the appropriateness and validity of this practice. Provided there are no directives (advance or current by resident or caregiver) limiting diagnostic or therapeutic interventions, all residents of LTCFs with suspected symptomatic infection should have appropriate diagnostic laboratory studies done promptly, and the findings should be discussed with the primary care clinician (see Recommendations). The most common infections among LTCF residents are urinary tract infections, respiratory infections, skin or soft tissue infections, and gastroenteritis. Decisions concerning possible transfer of an LTCF resident to an acute-care facility are best expressed through an advance directive or, when not available, through transfer policies developed by the LTCF. In general, LTCF residents have been transferred to an acute-care facility when any of the following conditions exist: (1) the resident is clinically unstable and the resident or family goals indicate aggressive interventions should be initiated, (2) critical diagnostic tests are not available in the LTCF, (3) necessary therapy or the mode of administration of therapy (frequency or monitoring) are beyond the capacity of the LTCF, (4) comfort measures cannot be assured in the LTCF, and (5) specific infection-control measures are not available in the LTCF.

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.

A comparison of diagnostic assays for the detection of type A swine influenza virus from nasal swabs and lungs

Nasal swabs and lung samples from pigs experimentally infected with H1N1 swine influenza virus (SIV) were examined for the presence of SIV by the indirect fluorescent antibody assay, immunohistochemistry, cell culture virus isolation, egg inoculation, and 2 human enzyme immunoassays (membrane enzyme immunoassay, microwell enzyme immunoassay). Egg inoculation was considered to be the gold standard for assay evaluation. The 2 human enzyme immunoassays (EIA) and egg inoculation agreed 100% for the prechallenge nasal swabs. Agreement on SIV identification in nasal swabs with egg inoculation following challenge was considered to be good to excellent for membrane EIA (kappa = 0.85) and microwell EIA (kappa = 0.86). Agreement on SIV identification in lung tissue with egg inoculation following challenge was good to excellent for membrane EIA (kappa = 0.75), fair for microwell EIA, fluorescent antibody, and cell culture virus isolation (kappa = 0.48, 0.64, 0.62, respectively), and poor for immunohistochemistry (kappa = 0.36). No assay was 100% accurate, including the "gold standard," egg inoculation. In light of this information, it is important to consider clinical signs of disease and a thorough herd history in conjunction with diagnostic results to make a diagnosis of SIV infection.

Predicting influenza infections during epidemics with use of a clinical case definition

Combined pharyngeal and nasal swab specimens were collected from 100 subjects who presented with a flu-like illness (fever >37.8 degrees C plus 2 of 4 symptoms: cough, myalgia, sore throat, and headache) of <72 hours' duration at 3 different clinics in the province of Quebec, Canada, during the 1998-1999 flu season. The rate of laboratory-confirmed influenza infection was 72% according to cell culture findings and 79% according to the results of multiplex reverse-transcription polymerase chain reaction (RT-PCR) analysis (85%, influenza AH3; 15%, influenza B). All subjects for whom these results were discordant (negative culture and positive PCR) presented with a temperature > or =38.2 degrees C as well as 3 or 4 of the symptoms in the clinical case definition. Stepwise logistic regression showed that cough (odds ratio [OR], 6.7; 95% confidence interval [CI], 1.4-34.1; P=.02) and fever (OR, 3.1; 95% CI, 1.4-8.0; P=.01) were the only factors significantly associated with a positive PCR test for influenza. The positive predictive value, negative predictive value, sensitivity, and the specificity of a case definition including fever (temperature of >38 degrees C) and cough for the diagnosis of influenza infection during this flu season were 86.8%, 39.3%, 77.6%, and 55.0%, respectively.