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

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

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

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

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

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

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

Case-based surveillance of influenza hospitalizations during 2004-2008, Colorado, USA

Case-based surveillance provides more information than any other influenza surveillance component.

Colorado became the first state to make laboratory-confirmed influenza-associated hospitalizations a case-based reportable condition in 2004. We summarized surveillance for influenza hospitalizations in Colorado during the first 4 recorded influenza seasons (2004–2008). We highlight the similarities and differences among influenza seasons; no 2 seasons were entirely the same. The 2005–06 influenza season had 2 distinct waves of activity (types A and B), the 2006–07 season was substantially later and milder, and 2007–08 had substantially greater influenza B activity. The case-based surveillance for influenza hospitalizations provides information regarding the time course of seasonal influenza activity, reported case numbers and population-based rates by age group and influenza virus type, and a measure of relative severity. Influenza hospitalization surveillance provides more information about seasonal influenza activity than any other surveillance measure (e.g., surveillance for influenza-like illness) currently in widespread use among states. More states should consider implementing case-based surveillance for influenza hospitalizations.

Estimating sensitivity of laboratory testing for influenza in Canada through modelling

BACKGROUND

The weekly proportion of laboratory tests that are positive for influenza is used in public health surveillance systems to identify periods of influenza activity. We aimed to estimate the sensitivity of influenza testing in Canada based on results of a national respiratory virus surveillance system.

METHODS AND FINDINGS

The weekly number of influenza-negative tests from 1999 to 2006 was modelled as a function of laboratory-confirmed positive tests for influenza, respiratory syncytial virus (RSV), adenovirus and parainfluenza viruses, seasonality, and trend using Poisson regression. Sensitivity was calculated as the number of influenza positive tests divided by the number of influenza positive tests plus the model-estimated number of false negative tests. The sensitivity of influenza testing was estimated to be 33% (95%CI 32-34%), varying from 30-40% depending on the season and region.

CONCLUSIONS

The estimated sensitivity of influenza tests reported to this national laboratory surveillance system is considerably less than reported test characteristics for most laboratory tests. A number of factors may explain this difference, including sample quality and specimen procurement issues as well as test characteristics. Improved diagnosis would permit better estimation of the burden of influenza.

The limitations of point of care testing for pandemic influenza: what clinicians and public health professionals need to know

As the world prepares for the next influenza pandemic, governments have made significant funding commitments to vaccine development and antiviral stockpiling. While these are essential components to pandemic response, rapid and accurate diagnostic testing remains an often neglected cornerstone of pandemic influenza preparedness. Clinicians and Public Health Practitioners need to understand the benefits and drawbacks of different influenza tests in both seasonal and pandemic settings. Culture has been the traditional gold standard for influenza diagnosis but requires from 1-10 days to generate a positive result, compared to nucleic acid detection methods such as real time reverse transcriptase polymerase chain reaction (RT-PCR). Although the currently available rapid antigen detection kits can generate results in less than 30 minutes, their sensitivity is suboptimal and they are not recommended for the detection of novel influenza viruses. Until point-of-care (POC) tests are improved, PILPN recommends that the best option for pandemic influenza preparation is the enhancement of nucleic acid-based testing capabilities across Canada.

Evaluation of a new rapid antigen test using immunochromatography for detection of human metapneumovirus in comparison with real-time PCR assay

A new rapid human metapneumovirus (hMPV) detection kit using immunochromatography (SAS hMPV test) was compared to real-time PCR for 224 nasal swab specimens, 96.4% of which were obtained from children of <15 years of age. The overall sensitivity and specificity were 82.3% and 93.8%, respectively, suggesting that this test is useful for pediatricians to diagnose hMPV infection in a clinical setting.

Seasonal influenza in adults and children--diagnosis, treatment, chemoprophylaxis, and institutional outbreak management: clinical practice guidelines of the Infectious Diseases Society of America

Guidelines for the treatment of persons with influenza virus infection were prepared by an Expert Panel of the Infectious Diseases Society of America. The evidence-based guidelines encompass diagnostic issues, treatment and chemoprophylaxis with antiviral medications, and issues related to institutional outbreak management for seasonal (interpandemic) influenza. They are intended for use by physicians in all medical specialties with direct patient care, because influenza virus infection is common in communities during influenza season and may be encountered by practitioners caring for a wide variety of patients.

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.

Quarantine for pandemic influenza control at the borders of small island nations

BACKGROUND

Although border quarantine is included in many influenza pandemic plans, detailed guidelines have yet to be formulated, including considerations for the optimal quarantine length. Motivated by the situation of small island nations, which will probably experience the introduction of pandemic influenza via just one airport, we examined the potential effectiveness of quarantine as a border control measure.

METHODS

Analysing the detailed epidemiologic characteristics of influenza, the effectiveness of quarantine at the borders of islands was modelled as the relative reduction of the risk of releasing infectious individuals into the community, explicitly accounting for the presence of asymptomatic infected individuals. The potential benefit of adding the use of rapid diagnostic testing to the quarantine process was also considered.

RESULTS

We predict that 95% and 99% effectiveness in preventing the release of infectious individuals into the community could be achieved with quarantine periods of longer than 4.7 and 8.6 days, respectively. If rapid diagnostic testing is combined with quarantine, the lengths of quarantine to achieve 95% and 99% effectiveness could be shortened to 2.6 and 5.7 days, respectively. Sensitivity analysis revealed that quarantine alone for 8.7 days or quarantine for 5.7 days combined with using rapid diagnostic testing could prevent secondary transmissions caused by the released infectious individuals for a plausible range of prevalence at the source country (up to 10%) and for a modest number of incoming travellers (up to 8000 individuals).

CONCLUSION

Quarantine at the borders of island nations could contribute substantially to preventing the arrival of pandemic influenza (or at least delaying the arrival date). For small island nations we recommend consideration of quarantine alone for 9 days or quarantine for 6 days combined with using rapid diagnostic testing (if available).

[Impact of influenza rapid diagnostic tests (IRDT) on the diagnosis of influenza and on the management of influenza in children in ambulatory pediatric setting]

OBJECTIVE

Several studies have highlighted the assets of the influenza rapid diagnostic tests (IRDT) for the emergency department management of febrile children. The objective of this study was to determine in ambulatory pediatric setting impact of IRDT on the management of febrile children during an epidemic, especially on other diagnostic testing performed, antibiotic and antiviral treatments.

METHODS

During an influenza epidemic, 37 paediatricians in three different areas of France included all children presenting fever with respiratory illnesses; they performed IRDT (test QuickVue for Influenza A and B, Quidel). Data collected were antiflu vaccination, previous asthma, symptoms, clinical signs, other diagnostic testing performed, and a follow-up two weeks later.

RESULTS

Between December, 2006 and April, 2007, 695 children entered the program. The average age of those children was 4.1 years old (SD 3.4), median 3.2 (0.07-17.5). In 41.6% of the cases, the tests proved positive. Among 13 symptoms of influenza, only five were significantly more present in the group IRDT+: shiver (68.1% versus 57.4%), asthenia (87% versus 79.9%), cough (87.5% versus 70.1%), rhinorrhea (93.4% versus 83.3%), and sleepiness (54.2% versus 43.4%). The number of laboratory tests and radiographs ordered were less frequent in group IRDT+ than in group IRDT-: respectively 0.7% versus 11.6%, and 0.7% versus 8.6% (p<0.0001). IRDT+ group received antibiotics in 7.6% of cases (22 patients, 20 for OMA) and antiviral in 64.7%. IRDT- group received respectively 18.5% antibiotics, and no antiviral (p<0.0001).

CONCLUSION

This study confirms the difficulty of clinical influenza diagnosis, and suggests the assets of IRDT to diagnose influenza and to improve the management of influenza in ambulatory paediatric setting.

Viral Infections

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

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

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

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

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

Development and implementation of a molecular diagnostic platform for daily rapid detection of 15 respiratory viruses

Acute respiratory tract infections are caused by a large number of viruses. Diagnostic methods have until recently been available only for a limited number of these viruses. With the objective to achieve sensitive assays for all respiratory viruses, a rational workflow in the laboratory, and a short turn-around time, a real-time PCR diagnostic platform for daily rapid detection of 15 respiratory viruses was developed. The system was evaluated on 585 stored nasopharyngeal aspirates from hospitalized children. Previous analysis by immunofluorescence and virus isolation identified viruses in 37% of the samples while the new PCR diagnostic panel detected 57% virus positive samples. The new platform was introduced in the laboratory in October 2007 and has then fully replaced the standard immunofluorescence assay for rapid detection of viruses and virus isolation.

Influenza

OBJECTIVE

Influenza is a major concern for intensivists in all communities in the U.S. While there is considerable concern whether or not the country will be ready for a pandemic influenza, even seasonal influenza poses a major challenge to hospitals. The objective of this review is to summarize current knowledge of influenza with emphasis on the issues that intensivist will encounter.

SETTING

Intensive care unit in a 450-bed, tertiary care, teaching hospital.

METHODS

Source data were obtained from a PubMed search of the medical literature. PubMed "related articles" search strategies were likewise employed frequently.

SUMMARY AND CONCLUSIONS

Seasonal influenza causes more than 200,000 hospitalizations and 41,000 deaths in the U.S. every year, and is the seventh leading cause of death in the U.S. Despite this impact there is a shortcoming in knowledge of influenza among many health care workers, and a paucity of clinical data and studies to guide therapy. Intensivists need to recognize the importance of seasonal influenza as a cause of severe morbidity and mortality. This review summarizes current knowledge of the diagnosis, complications, therapy, and infection control measures associated with influenza.

Analytical and clinical sensitivity of the 3M rapid detection influenza A+B assay

The performance of the 3M rapid detection influenza A+B (3M flu) assay was compared to the performance of other immunochromatographic assays. The clinical and analytical performance of the 3M flu assay was superior to that of BinaxNOW and Directigen EZ assays and equivalent to that of the QuickVue assay. The 3M flu assay offers an objective output and direct linkage to laboratory information systems.

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.

Real-time PCR compared to Binax NOW and cytospin-immunofluorescence for detection of influenza in hospitalized patients

BACKGROUND

Rapid tests have had a significant impact on influenza diagnosis, but more accurate tests are needed for hospitalized patients who test negative by rapid methods.

OBJECTIVE

We sought to determine the increased yield obtained from influenza RT-PCR in hospitalized patients compared to two rapid methods.

STUDY DESIGN

Binax NOW, cytospin-enhanced direct immunofluoroescence (DFA), and influenza A and B multiplex TaqMan RT-PCR were performed on 237 clinical samples.

RESULTS

Binax NOW detected 70 (53.0%), cytospin-DFA detected 127 (96.2%), and TaqMan RT-PCR detected 132 (100%) influenza-positive samples. The difference in sensitivity was significant between RT-PCR and Binax NOW (p<0.0001), but not between RT-PCR and cytospin-DFA (p=0.0736). Two samples testing positive for influenza B by all three methods, tested falsely positive for influenza A by Binax. Eight true positive samples did not become reactive by Binax until 30 min, and thus were counted as negative.

CONCLUSIONS

The accuracy of real-time RT-PCR should greatly improve the diagnosis of influenza in hospitals using simple rapid flu tests, but may have a more modest impact in hospitals with expertise in cytospin-DFA. Further studies are needed to determine the effect of influenza RT-PCR on patient management and costs in hospitalized patients.

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

BACKGROUND

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSIONS

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

Rapid molecular detection of influenza outbreaks in nursing homes

BACKGROUND

Nursing home influenza outbreaks occur in spite of established vaccination programs, and require rapid and sensitive laboratory confirmation for timely intervention.

OBJECTIVES

To evaluate diagnostic approaches for rapid confirmation of nursing home influenza outbreaks.

STUDY DESIGN

Influenza virus real-time PCR and Directigen Flu A+B enzyme immunoassay were performed on nasopharyngeal swabs, nasopharyngeal washes and throat swabs collected from residents with clinical suspicion of influenza during seven probable nursing home outbreaks in 2004-2005 and 2005-2006. The efficacy of specimen sampling and transport management by Public Health Service outbreak team was evaluated.

RESULTS

PCR detected influenza RNA in 80% (68/85) of specimens from 81% (38/47) residents, confirming six suspected outbreaks. Immunoassay sensitivity was highest on nasopharyngeal swabs (38%; 11/29) with a positive predictive value of 100% compared to PCR. Nasopharyngeal swabs were equally sensitive to nasopharyngeal washes by PCR. Nasopharyngeal wash sampling appeared unpractical due to common underlying disability of residents. Outbreak team support was associated with a shorter time to PCR diagnosis compared to outbreaks with no logistical support (mean, 28.2h vs. 84h; P=0.05).

CONCLUSIONS

Influenza real-time PCR on nasopharyngeal swabs, obtained by Public Health Service outbreak teams, enabled rapid and sensitive confirmation of nursing home influenza outbreaks.

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

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