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Performance of rapid-test kits for the detection of the pandemic influenza A/H1N1 virus

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Journal of Virological Methods 173 (2011) 387–389

Contents lists available atScienceDirect

Journal of Virological Methods

j o u r n a l h o m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / j v i r o m e t

Short communication

Performance of rapid-test kits for the detection of the pandemic influenza

A/H1N1 virus

Kuo-Chien Tsao

a,b,c,1

, Yung-Bin Kuo

b,d,1

, Chung-Guei Huang

a,b,c

, Shao-Wen Chau

e

, Err-Cheng Chan

b,∗

aDepartment of Laboratory Medicine, Chang Gung Memorial Hospital, Taoyuan, Taiwan

bDepartment of Medical Biotechnology and Laboratory Science, Chang Gung University, Taoyuan, Taiwan cResearch Center for Emerging Viral Infections, Chang Gung University, Taoyuan, Taiwan

dDepartment of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan eDepartment of Laboratory Medicine, Chang Gung Memorial Hospital, Keelung, Taiwan

Article history: Received 12 July 2010

Received in revised form 1 February 2011 Accepted 10 February 2011

Available online 17 February 2011 Keywords:

Influenza A virus H1N1 Pandemic

Rapid influenza diagnostic test

a b s t r a c t

The early detection of pandemic influenza strains is a key factor for clinicians in treatment decisions and infection control practices. The aims of this study were to determine the analytical sensitivity and clinical performance of the commercially available influenza rapid tests in Taiwan. Four rapid tests for influenza virus (BinaxNow test, QuickVue test, TRU test, and Formosa Rapid test) were evaluated for their detection limit against four influenza viruses (the 2009 pandemic influenza A virus H1N1, seasonal influenza virus H1N1, H3N2, and influenza B virus) circulating in Taiwan. The viral load of these isolates were quantified by rtRT-PCR and then diluted 2-fold serially for the comparison. The lowest detectable viral load of the pandemic influenza A virus H1N1 by the Formosa Rapid test, QuickVue test, TRU test, and Binax Now test was 5.3× 104, 1.0× 105, 1.0× 105, and 4.2× 105copies/␮L, respectively. Of these four tests, the two most

sensitive tests (the QuickVue test and the Formosa Rapid test) were chosen to evaluate 62 nasopharyngeal specimens from patients who were suspected of infection with pandemic influenza A virus H1N1. The positive rate for the Formosa Rapid test and the QuickVue test were 53.2% (33/62) and 45.2% (28/62) (McNemar’s test, P = 0.125), respectively. In conclusion, the Formosa Rapid test was the most sensitive test in the present study for the detection of influenza antigens and its clinical performance was similar to that of the QuickVue test (Kappa = 0.776). This suggests that the Formosa Rapid test could be used to aid clinical decision making in primary health care settings during outbreaks of influenza.

© 2011 Elsevier B.V. All rights reserved.

1. Introduction

A novel influenza A (H1N1) virus, originating in swine and resulting from the recombination of human, avian, and swine influenza viruses, was identified as the cause of a 2009 pan-demic outbreak of febrile respiratory infection (Baden et al., 2009; Dawood et al., 2009). Influenza-like illness is characterized by clin-ical symptoms including fever above 38◦C, coughing, sore throat, rhinitis, myalgia, fatigue, and vomiting (Nicholson, 1992). The rapid diagnosis of patients possibly infected with swine influenza viruses, especially those at high risk of influenza-related complications, is essential not only for the initiation of antiviral treatment but also for surveillance of the infection.

When diagnosing influenza infection, both the accuracy and the time frame in which a result is obtained are important. The

∗ Corresponding author. Tel.: +886 3 2118800x5220; fax: +886 3 2118741. E-mail address:chanec@mail.cgu.edu.tw(E.-C. Chan).

1The two authors contributed equally to this study.

rate of clinical diagnosis of pandemic influenza A virus H1N1 have been reported to range from 63% to 86% in comparison to labora-tory diagnosis by reverse transcription-polymerase chain reaction (RT-PCR) or viral culture (Boivin et al., 2000; Monto et al., 2000; Ruest et al., 2003). Currently, laboratory identification of influenza-specific RNA by RT-PCR is the reference method for the diagnosis of influenza virus infection. However, due to the requirement for spe-cialized equipment, RT-PCR cannot be conducted readily in primary health care settings. The pandemic 2009 outbreak has highlighted the need for a rapid influenza diagnostic test to facilitate early treatment of infected individuals because treatment has been ben-eficial only when antiviral drugs are administered within 48 h of the appearance of symptoms (Treanor et al., 2000). In the clinic, several rapid influenza diagnostic tests that can provide results in a clini-cally relevant time frame to assist clinical judgment have become available. Recent studies evaluating the accuracy of rapid influenza diagnostic test results using clinical specimens have shown a broad sensitivity range from 10% to 69% (Chan et al., 2009; Faix et al., 2009; Ginocchio et al., 2009; Vasoo et al., 2009). However, little is known about the sensitivity and the specificity of rapid tests for 0166-0934/$ – see front matter © 2011 Elsevier B.V. All rights reserved.

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388 K.-C. Tsao et al. / Journal of Virological Methods 173 (2011) 387–389

Table 1

Comparison of the detection limits of different commercially available influenza virus rapid detection kits.

Influenza virus subtype Detection limit (titer/viral load)

Viral load (copies/␮L) Formosa One Sure Flu A/B Rapid test QuickVue Influenza A + B test TRU Flu A/B test BinaxNow influenza A&B test

swH1N1 3.4× 106 1:64/5.3× 104 1:32/1.0× 105 1:32/1.0× 105 1:8/4.2× 105

H1N1 1.5× 107 1:256/5.9× 104 1:64/2.4× 105 1:64/2.4× 105 1:16/9.5× 105

H3N2 3.0× 106 1:36/9.4× 104 1:16/1.8× 105 1:8/3.8× 105 1:2/1.5× 106

Influenza B 1.7× 107 1:8/2.1× 106 1:16/1.0× 106 1:8/2.0× 106 1:8/2.0× 106

the detection of the new pandemic influenza A virus. This uncer-tainty in the clinical performance of rapid influenza diagnostic tests for the detection of the H1N1 strain in patients with influenza-like illnesses during outbreaks prompted this study.

This study aimed to (1) determine the analytical capability of rapid tests to detect the new pandemic influenza A by comparison with seasonal influenza A viruses and (2) conduct a head-to-head comparison of two selected rapid influenza diagnostic tests for their diagnostic performance for detecting pandemic influenza A virus H1N1 in clinical specimens.

Four seasonal Influenza virus strains which circulated in Taiwan, pandemic H1N1 virus A/California/04/2009 (swH1N1), seasonal influenza virus A/Brisbane/59/2007 (H1N1), A/Brisbane/10/2007 (H3N2), and B/Brisbane/60/2008, were isolated and amplified in Madin–Darby canine kidney epithelial cells to prepare viral stocks. After 3 days incubation, the viral supernatant was harvested, and the viral load was quantified using a standard real-time RT-PCR assay (rtRT-PCR) (Ward et al., 2004), and then diluted serially for the comparison. The limit of detection of each rapid test is denoted as the lowest viral load (copies/␮L) detectable.

Sixty-two nasopharyngeal swabs were obtained from patients at the Chang-Gung Memorial Hospital (Taoyuan, Taiwan) suspected of infection with the pandemic influenza A virus H1N1 in August, 2009. All specimens were collected within 1–2 days of the develop-ment of symptoms, kept at 4◦C in the vial transport media and sent to the laboratory immediately. After the extraction process, 120␮L and 340␮L aliquots of extracts were applied for the Formosa Rapid test and QuickVue rapid tests, respectively. All tests were processed within 12 h of reception in the laboratory.

Four rapid tests for influenza virus, Binax Now Influenza A&B (Binax; Portland, USA), QuickVue Influenza A + B test (Quidel; San Diego, USA), TRU Flu A/B (Meridian Biosciences; Cincinnati, USA), and Formosa One Sure Flu A/B Rapid test (Formosa Biomedical Technology Corp.; Yilan, Taiwan), were compared for their ability to detect influenza antigens following each of the manufacturer’s specific protocols. For evaluation of clinical diagnostic efficacy, the two relatively more sensitive tests (the well studied QuickVue test and the Formosa Rapid test produced in Taiwan) were selected for detection of pandemic influenza A virus H1N1 in clinical specimens collected from patients with an influenza-like illness by a trained technician who was blinded to the other test results.

As shown inTable 1, the detection limits ranged from 104 to

106copies/␮L between the different commercial rapid influenza

diagnostic tests. The sensitivity also varied between the dif-ferent influenza subtypes. All of the rapid influenza diagnostic tests had greater sensitivity for detecting influenza A virus (104

to 105copies/␮L) than influenza B virus (106copies/␮L). For

the detection of pandemic influenza A virus H1N1 2009, the detection limit of the Formosa Rapid test, QuickVue test, TRU test, and Binax Now test was 5.3× 104, 1.0× 105, 1.0× 105, and

4.2× 105copies/␮L, respectively. The clinical diagnostic efficacy of

the two tests selected is shown inTable 2. The Formosa Rapid test and the QuickVue test had a positive rate of 53.2% (33/62) and 45.2% (28/62), respectively (McNemar’s test, P = 0.125). Six spec-imens (6/62; 9.7%) that are not detected by the QuickVue test demonstrated positive results by the Formosa Rapid test.

Table 2

Comparison of the performance of the Formosa One Sure Flu A/B Rapid test and the QuickVue Influenza A + B test to clinical definitions of influenza-like illness for the detection of pandemic influenza A/H1N1 2009.a,b

QuickVue Influenza A + B test

Positive Negative Total

Formosa One Sure Flu A/B Rapid test

Positive 27 6 33

Negative 1 28 29

Total 28 34

Difference between the Formosa One Sure Flu A/B Rapid test and the QuickVue Influenza A + B test were not significant.

aMcNemar’s test P = 0.125. bKappa value = 0.776.

According to the surveillance information, the first outbreak of influenza A/H1N1 was in the 36th week of 2009, and was shown to be the major pandemic strain which accounted for nearly 88.2% of all community influenza strains which have been isolated. In clinical practice, based on the clinical treatment guidelines of the Taiwan Center for Disease Control, patients with influenza-like illness and positive by rapid influenza diagnostic test should be treated with antiviral drugs immediately (Chen et al., 2009).

The existing rapid influenza diagnostic tests, produced by using a monoclonal antibody against the influenza nucleoprotein, were designed for detection of seasonal influenza A and B and not the pandemic influenza A virus H1N1 (Yang et al., 2008). The pandemic influenza A virus H1N1 strain is different from the common human influenza A virus because it combines genes from avian, human, and swine influenza viruses (Dawood et al., 2009). Commercial rapid influenza diagnostic tests have been shown to have a broad range in sensitivity for detecting the influenza A virus H1N1 virus (CDC, 2009; Chan et al., 2009; Vasoo et al., 2009). Therefore, it is nec-essary to determine whether the rapid influenza diagnostic tests can detect pandemic influenza A virus H1N1 as efficiently as they detect seasonal influenza viruses.

The first objective of this study was to evaluate the detection limit of four rapid influenza diagnostic tests against a panel of standard influenza virus strains. Among them, the QuickVue test and the TRU test had a similar detection limit for influenza A virus H1N1 where the viral load was as low as 1.0× 105copies/␮L.

How-ever, the BinaxNow test detected only viral loads greater than 4.2× 105copies/␮L. Similar results were reported by Ginocchio

et al. (2009)who found that the performance of the QuickVue test was better than the BinaxNow test for the detection of the H1N1 influenza virus.

Compared with the other rapid influenza diagnostic tests, the Formosa Rapid test is the most sensitive kit, with a sensitivity of 104copies/␮L for all influenza A virus subtypes, including

pan-demic influenza A virus H1N1, seasonal influenza virus H1N1, and H3N2. Overall, the detection limit of the different commercial rapid influenza diagnostic tests varied between different influenza sub-types and ranged from 104to 106copies/␮L, which is 103to 104

times less sensitive than rtRT-PCR. This may explain why rapid tests could not detect the virus in specimens with a lower viral titer.

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K.-C. Tsao et al. / Journal of Virological Methods 173 (2011) 387–389 389 The data on the analytical sensitivity for detection of cultured

virus strains may not reflect accurately the sensitivity in clinical specimens. Therefore, in order to evaluate the clinical diagnostic efficacy, an extensive head-to-head comparison for detection of pandemic influenza A virus H1N1 in clinical pharyngeal specimens was conducted. The results showed that the diagnostic efficacy of the Formosa Rapid test was comparable to that of the QuickVue test (Kappa = 0.776). At 50%, the positive rate of both rapid influenza diagnostic tests is similar to previous studies which demonstrated that the QuickVue test had a sensitivity of 53–69% and specificity of 100% for pandemic influenza A virus H1N1 (CDC, 2009; Hurt et al., 2007; Vasoo et al., 2009).

In summary, this study demonstrated that the analytical sen-sitivity of the Formosa Rapid test for the detection of pandemic influenza A virus H1N1 was found to be slightly superior to the other commercial tests. The clinical performance of the Formosa Rapid test was comparable with the QuickVue test. Since the For-mosa Rapid test can be completed rapidly and does not require extensive laboratory facilities, it may be helpful in the timely detection of highly contagious pandemic influenza A virus H1N1 infections.

References

Baden, L.R., Drazen, J.M., Kritek, P.A., Curfman, G.D., Morrissey, S., Campion, E.W., 2009. H1N1 influenza A disease—information for health professionals. N. Engl. J. Med. 360, 2666–2667.

Boivin, G., Hardy, I., Tellier, G., Maziade, J., 2000. Predicting influenza infections during epidemics with use of a clinical case definition. Clin. Infect. Dis. 31, 1166–1169.

CDC, 2009. Evaluation of rapid influenza diagnostic tests for detection of novel influenza A (H1N1) virus—United States, 2009. MMWR Morb. Mortal. Wkly. Rep. 58, 826–829.

Chan, K.H., Lai, S.T., Poon, L.L., Guan, Y., Yuen, K.Y., Peiris, J.S., 2009. Analytical sensi-tivity of rapid influenza antigen detection tests for swine-origin influenza virus (H1N1). J. Clin. Virol. 45, 205–207.

Chen, W.L., Chang, W.H., Chen, C.C., Hsieh, J.C., Shih, Y.Y., Chen, Y.L., 2009. Ambula-tion study of a woman with paraplegia using a reciprocating gait orthosis with functional electrical stimulation in Taiwan: a case report. Disabil. Rehabil. Assist. Technol. 4, 429–438.

Dawood, F.S., Jain, S., Finelli, L., Shaw, M.W., Lindstrom, S., Garten, R.J., Gubareva, L.V., Xu, X., Bridges, C.B., Uyeki, T.M., 2009. Emergence of a novel swine-origin influenza A (H1N1) virus in humans. N. Engl. J. Med. 360, 2605–2615. Faix, D.J., Sherman, S.S., Waterman, S.H., 2009. Rapid-test sensitivity for novel

swine-origin influenza A (H1N1) virus in humans. N. Engl. J. Med. 361, 728–729.

Ginocchio, C.C., Zhang, F., Manji, R., Arora, S., Bornfreund, M., Falk, L., Lotlikar, M., Kowerska, M., Becker, G., Korologos, D., de Geronimo, M., Crawford, J.M., 2009. Evaluation of multiple test methods for the detection of the novel 2009 influenza A (H1N1) during the New York City outbreak. J. Clin. Virol. 45, 191–195. Hurt, A.C., Alexander, R., Hibbert, J., Deed, N., Barr, I.G., 2007. Performance of six

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Monto, A.S., Gravenstein, S., Elliott, M., Colopy, M., Schweinle, J., 2000. Clinical signs and symptoms predicting influenza infection. Arch. Intern. Med. 160, 3243–3247.

Nicholson, K.G., 1992. Clinical features of influenza. Semin. Respir. Infect. 7, 26–37. Ruest, A., Michaud, S., Deslandes, S., Frost, E.H., 2003. Comparison of the Directi-gen 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. J. Clin. Microbiol. 41, 3487–3493.

Treanor, J.J., Hayden, F.G., Vrooman, P.S., Barbarash, R., Bettis, R., Riff, D., Singh, S., Kinnersley, N., Ward, P., Mills, R.G., 2000. Efficacy and safety of the oral neuraminidase inhibitor oseltamivir in treating acute influenza: a randomized controlled trial. US Oral Neuraminidase Study Group. JAMA 283, 1016–1024. Vasoo, S., Stevens, J., Singh, K., 2009. Rapid antigen tests for diagnosis of pandemic

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