Evaluation of BioStar FLU OIA assay for rapid detection of influenza A and B viruses in respiratory specimens.

BACKGROUND: Demand for the rapid diagnosis of influenza infections has increased with the advent of the availability of neuraminidase antiviral therapy for influenza A and B. Several rapid assays that detect both influenza A and B are now available. OBJECTIVES: In this study we compared the performance of the BioStar FLU OIA assay to Bartels Viral Respiratory Screening and Identification Kit (Bartels Inc., Issaquah, WA), and cell culture. STUDY DESIGN: A total of 145 patient specimens for influenza virus detection submitted in either viral transport medium or in sterile containers were evaluated by the three methods. Specimen types included nasal washings, nasal swabs, sputum, throat swabs, and bronchial alveolar lavage (BAL) fluids. RESULTS: Fifty six positive specimens were identified based on culture and/or DFA. Of these, 30 specimens were positive by the OIA assay for an overall sensitivity of 54%. The OIA assay detected 48% (n = 21) of the 44 culture positive specimens and 81% (n = 29) of the 36 DFA positive specimens. Eighty six of the 89 culture/DFA negative samples were negative by the OIA assay (97% specificity). Analysis of the OIA assay sensitivity from samples submitted in M4 transport medium or in sterile containers revealed that M4 transport medium does not reduce the sensitivity of the OIA assay. Fifteen of the 27 positive samples submitted in M4 transport medium were positive by the OIA assay (56% sensitivity) compared to 15 of 29 positive samples transported in sterile containers (52% sensitivity). Twelve specimens were either culture and/or DFA positive for viruses other than influenza, but negative by the OIA assay, suggesting that there was no cross reactivity of the OIA assay with the other virus types recovered in this study. CONCLUSIONS: The overall excellent specificity of the BioStar FLU OIA allows for treatment of positive patients for influenza, however, a negative result should be confirmed by DFA and culture.     

Performance of virus isolation and Directigen Flu A to detect influenza A virus in experimental human infection.

BACKGROUND: Few data exist to assess the sensitivity of different specimen types for viral detection during the course of influenza virus infection. OBJECTIVES: This study assessed the relationships between quantitative influenza A virus replication and antigen detectability by the enzyme immunosorbent assay (EIA) Directigen Flu A in different type of samples during experimental human infection. STUDY DESIGN: Fourteen volunteers were inoculated with influenza A virus A/Texas/36/91 (H1N1). Four specimens types were collected in sequence for quantitative isolation in cell culture and antigen testing from days 1 to 8 after inoculation. RESULTS: Seventy-one (63%) of nasopharyngeal wash specimens were culture positive, compared to 51 (46%) of throat gargles, 51 (46%) of nasal swabs, and 27 (24%) of throat swabs. All subjects shed virus in their nasopharyngeal wash at least one day and 86% of subjects had a positive nasopharyngeal wash culture on day 2 after inoculation. The mean viral titers were highest on day 2 post inoculation for all specimen types and averaged 3.6 log10 TCID50/ml for nasal washes, 1.2 log10 TCID50/ml for throat gargles, 1.8 log10 TCID50/ml for the nasopharyngeal swabs, and 0.6 log10 TCID50/ml for the throat swabs. Mean viral titers in the nasal washes were significantly different (P<0.05) compared to other specimen types. The peak of sensitivity of EIA (compared to culture) was the second day after inoculation. Nasopharyngeal and throat swab results were combined for this analysis and considered positive by culture if positive in either or both samples. Thus, on day 2 the number of EIA positive samples relative to the number culture positive was 9/12 (75%) for nasopharyngeal wash specimens, 2/9 (22%) for throat gargles, and 7/11 (64%) for the combined throat and nasal swabs specimens. CONCLUSIONS: Nasopharyngeal washes are the most sensitive sample type detecting influenza A virus in adults. For rapid diagnosis the Directigen Flu A is an alternative with a sensitivity compared to culture ranging between 64 and 78% if performed on nasopharyngeal specimens on day two or three after experimental infection in adults. However, if performed on other specimens or later in the course of infection the sensitivity is lower.     

Evaluation of an Optical Immunoassay for the Rapid Detection of Influenza A and B Viral Antigens

 An optical immunoassay for the rapid detection of influenza types A and B viral antigens, FLU OIA (Biostar, USA), was prospectively compared with antigen detection methods and cell culture on 400 respiratory specimens during an influenza outbreak that occurred in Switzerland in 1998/1999. The FLU OIA had an overall sensitivity of 64.4% (95%CI, 56.3–71.7%) and a specificity of 94.9% (95%CI, 89.8–97.7%). Using specimens from pediatric and adolescent patients, the sensitivity obtained (71.8%; 95%CI, 61.7–80%) was different than that achieved with specimens from adult patients (51.4%; 95%CI, 36.5–65%) (P=0.004). The results show that rapid diagnostic tests with higher sensitivity and specificity for the detection of influenza virus are needed.     

Review of Rapid Diagnostic Tests for Influenza

Influenza is unique among viral infections because of its propensity for seasonal epidemics and occasional pandemics, and because of the morbidity and mortality that result from its pulmonary complications. In contrast to the majority of viruses, effective well-tolerated influenza vaccines, antivirals and chemoprophylaxis are available. The need for a timely diagnosis, which allows for optimal use of these treatments, led to the introduction of numerous rapid diagnostic tests (with turnaround times of less than 30 minutes). However, during influenza season, clinical diagnosis (based on cough and high fever of acute onset) can be highly predictive of influenza. Thus diagnostic tests are not required for all patients with suspected influenza but may be of value if the clinical diagnosis is unclear and if antiviral or antibiotic treatment is a consideration. When evaluating performance of various rapid diagnostic tests for influenza, it is important to consider the type and quality of specimen and type of patient to be tested. Specimen-type drives performance of the rapid diagnostic tests. Swab specimens, particularly throat swabs are the most frequently submitted but least desirable specimen-type. Thus, although current rapid diagnostic tests are specific for influenza, sensitivity is highly variable. To improve diagnostic accuracy, a nasal/nasopharyngeal aspirate or sputum specimen should be obtained. Because of their highly variable sensitivity and negative predictive value, it is our opinion, that rapid diagnostic tests should only be used in influenza season and that results should be confirmed with virus culture. Despite these reservations, during influenza-season, detection of influenza by rapid diagnostic test may, potentially, be of great benefit to the patient and public health.     

Type- and subtype-specific detection of influenza viruses in clinical specimens by rapid culture assay.

A rapid culture assay which allows for the simultaneous typing and subtyping of currently circulating influenza A(H1N1), A(H3N2), and B viruses in clinical specimens was developed. Pools of monoclonal antibodies (MAbs) against influenza A and B viruses and MAbs HA1-71 and HA2-76, obtained by immunizing mice with the denatured hemagglutinin subfragments HA1 and HA2 of influenza virus A/Victoria/3/75, were used for immunoperoxidase staining of antigens in infected MDCK cells. MAb HA1-71 reacted exclusively with influenza A viruses of the H3 subtype, while MAb HA2-76 reacted with subtypes H1, H3, H4, H6, H8, H9, H10, H11, and H12, as determined with 78 human, 4 swine, and 10 avian influenza virus reference strains subtyped by the hemagglutination inhibition test. To determine if the technique can be used as a rapid diagnostic test, 263 known influenza virus-positive frozen nasal or throat swabs were inoculated into MDCK cells. After an overnight incubation, the cells were fixed and viral antigens were detected by immunoperoxidase staining. Influenza A viruses of the H1 and H3 subtypes were detected in 31 and 113 specimens, respectively. The subtypes of 10 influenza A virus-positive specimens could not be determined because they contained too little virus. Influenza B viruses were detected in 84 specimens, and 25 specimens were negative. We conclude that this assay is a rapid, convenient, non-labor-intensive, and relatively inexpensive test for detecting, typing, and subtyping influenza viruses in clinical specimens.     

Novel, rapid optical immunoassay technique for detection of group A streptococci from pharyngeal specimens: comparison with standard culture methods.

A novel immunoassay system based on the changes in the reflection of light, termed an optical immunoassay (OIA), was utilized to directly detect group A streptococcal (GAS) carbohydrate antigen from clinical specimens. In two studies, a total of 1,275 throat swabs were tested for the presence of this antigen with the Strep A OIA rapid detection system and the results were compared with those of standard culture methods. In both studies, the Strep A OIA yielded more positive results than plating of the throat swab onto a selective agar, Trypticase soy agar containing sheep blood, or an enriched broth. In one study, the sensitivity and specificity of Strep A OIA compared with those of the broth-enriched culture were 97.4 and 95.6%, respectively. In a second study a sensitivity of 98.9% and a specificity of 98.6% were achieved. It was also shown that the carbohydrate antigen could be detected in the absence of viable GAS organisms. The Strep A OIA is an easily interpretable method and was shown to be more sensitive than routine culture methods for detecting GAS infections directly from throat swabs.     

Decreased leukocytes and other characteristics of laboratory findings of influenza virus infections in children

BACKGROUND AND PURPOSE: An outbreak of influenza A and influenza B appeared at the beginning and end of 2006 in southern Taiwan. We conducted this study to test whether laboratory findings could differentiate influenza A from influenza B infection. METHODS: All children aged 16 years or less, who had nasal and/or throat swabs sent from inpatient or outpatient settings at National Cheng Kung University Hospital for the diagnosis of influenza infection from January 2005 to February 2007, were considered eligible subjects. Retrospective chart review of clinical and laboratory data was performed. RESULTS: 274 patients were enrolled, 151 with influenza A and 123 with influenza B, of whom 127 (46.4%) received laboratory examinations. The peak month of influenza A and influenza B infections was January 2006 and January 2007, respectively. Children with influenza B infections were older than those with influenza A infections (p<0.001). Influenza B-infected patients were more likely to have myalgia (p=0.004) than those with influenza A infections. Furthermore, children with influenza B infections tended to have lower leukocyte counts (6383 +/- 3970/mm(3) vs 7639 +/- 3476/mm(3), p=0.004), and higher serum creatine kinase level (p=0.002) than those with influenza A infections. The clinical outcomes were usually favorable. CONCLUSIONS: The clinical features of influenza B and influenza A infections are similar. However, decreased leukocytes and increased serum creatine kinase can be used as adjunctive criteria for diagnosis of influenza B infection before viral culture results are available.     

Development and evaluation of a line probe assay for rapid typing of influenza viruses and detection of the H274Y mutation

Adequate treatment of influenza requires identification of viral type as well as detection of mutation(s) conferring drug resistance. Reverse hybridization-based line probe assays (LiPA) can be performed using several probes immobilized on nitrocellulose, strips enabling LiPA to determine simultaneously viral subtypes and detect the presence or absence of the H274Y mutation, which confers oseltamivir resistance of H1N1 influenza viruses. LiPA was developed for identification of H1N1 influenza virus subtypes (pandemic 2009 and seasonal types), as well as H3N2 and B subtypes, and to detect the H274Y mutation. The diagnostic capability of this assay was evaluated using cultured virus isolates as well as nasal swabs obtained from patients suspected of infection with influenza. In examining 354 cultured virus isolates, the LiPA showed 100% specificity for virus typing and 99% specificity for detecting the H274Y mutation. In 49 nasal swabs from a clinical study, the assay showed 100% specificity for virus typing and 88% specificity for detecting the absence of the H274Y mutation, although none of these swabs was PCR-positive for this mutation. These findings indicate that LiPA for influenza viruses may be used to monitor viral trends during the influenza season.     

Evaluation and clinical validation of an alcohol-based transport medium for preservation and inactivation of respiratory viruses

The clinical and public health importance of influenza and other respiratory viruses has accelerated the development of highly sensitive molecular diagnostics, but data are limited regarding preanalytical stages of diagnostic testing. We evaluated CyMol, an alcohol-based transport medium, for its ability to maintain specimen integrity for up to 21 days of storage at various temperatures; for its ability to inactivate virus; and for its compatibility with antigen- or nucleic acid-based diagnostics for respiratory viruses in clinical samples. In mock-infected samples, both universal transport medium (UTM-RT) and CyMol maintained equivalent viral quantities for at least 14 days at room temperature or colder, whereas a dry swab collection maintained viral quantities only if refrigerated or frozen. CyMol inactivated influenza virus within 5 min of sample immersion. UTM-RT- and CyMol-collected nasal swab specimens from 73 symptomatic students attending a campus health clinic were positive for a respiratory virus in 56.2% of subjects by multiplex PCR testing, including influenza A and B viruses, rhinovirus/enteroviruses, coronaviruses, respiratory syncytial virus, parainfluenza viruses, metapneumovirus, and adenovirus. Detection by PCR was equivalent in UTM-RT- and CyMol-collected specimens and in self- and staff-collected swabs. Direct fluorescent antibody (DFA) testing was substantially less sensitive (23.3%) than multiplex PCR, and DFA testing from UTM-RT-collected swabs was more sensitive than that from CyMol-collected swabs. These data indicate that an alcohol-based transport medium such as CyMol preserves respiratory virus integrity, rapidly inactivates viruses, and is compatible with PCR-based respiratory diagnostics.     

Comparison of direct immunofluorescent staining of clinical specimens for respiratory virus antigens with conventional isolation techniques.

Staining of clinical respiratory specimens obtained by nasopharyngeal and throat swabs with direct fluorescein isothiocyanate-conjugated antisera to para-influenza virus types 1, 2, and 3, influenza A virus, respiratory syncytial virus, adenovirus, mumps virus, and measles virus was compared with isolation procedures in routine tissue culture systems. Direct staining of clinical specimens with the commercially available conjugated offered a rapid means of diagnosing respiratory infections on a routine clinical basis when used in conjunction with isolation in tissue culture systems. Of 292 patients who were culture positive for these viruses, 259 were diagnosed by detection of the viral antigen in clinical specimens by direct immunofluorescence. No specimens that subsequently yielded a different respiratory virus by culture were positive by the direct immunofluorescence method. Use of selected antisera based on clinical history of the patient reduced the cost of rapid viral diagnosis.     

Surveillance of Childhood Influenza Virus Infection: What Is the Best Diagnostic Method To Use for Archival Samples?

Despite the clinical importance of influenza virus in pediatric respiratory infections, the optimal set of diagnostic tests to use when conducting studies using archival samples is not clear. In this study, we compared diagnostic tests for influenza virus in 75 children younger than 5 years of age who presented with symptomatic respiratory infection during one of four influenza seasons, had negative viral cultures for other respiratory pathogens, and had both an archival nasal aspirate obtained at the time of illness and serology spanning that influenza season. For all eligible children, we compared the results of viral culture performed at the time of collection with serology and PCR of archival nasal aspirates. Using real-time viral culture as the "gold standard," the test characteristics of PCR of archival nasal aspirates (sensitivity, 82%; specificity, 100%) and serology (sensitivity, 82%; specificity, 87%) were similar. The relatively low sensitivity of PCR of archival nasal samples in this study compared to that of PCR of fresh samples in a previous study suggests that RNA degradation occurred despite storage of the specimens at -70 degrees C. RNA degradation would also explain why only 11 (52%) of 21 archival nasal samples that had positive influenza virus cultures at the time of collection had positive repeat cultures in the summer of 2000. Thus, in archival specimens stored at -70 degrees C, PCR was more sensitive than viral culture. However, testing of fresh specimens had the highest yield in this study. Studies of optimal methods for specimen storage are needed.     

Laboratory test performance in young adults during influenza outbreaks at World Youth Day 2008

BackgroundThe performance of influenza laboratory diagnostics in young adults and in the setting of outbreaks during mass gatherings has not been well studied.ObjectivesWe compare the performance of point-of-care tests (POCTs) and immunofluorescence assays (IFAs) with nucleic acid tests (NATs) and viral culture in pilgrims attending influenza clinics established during a large influenza outbreak (World Youth Day, Sydney, Australia, 2008) to assess their performance under the real-life pressures of a mass influenza outbreak.Study designPatients with an influenza-like illness (ILI) underwent respiratory specimen sampling. Combined deep nares and throat swabs were collected for POCT by trained or untrained clinic staff; type-specific IFA; NAT and viral culture. Laboratory-confirmed influenza occurred if viral culture and/or NAT were positive; the performance of laboratory tests was calculated against this ‘gold standard’.ResultsA total of 230 samples were collected from 227 patients (median age, 20 years; interquartile range, 18–28 years), with 95 samples (41.3%) having laboratory-confirmed influenza infection (influenza A, 57; influenza B, 38). IFA and POCT sensitivities were 74.5% and 55%, respectively. Four of 51 (8%) culture-positive specimens were negative by NAT, and several errors in influenza virus typing occurred with IFA, POCT and NAT. A non-significant trend towards better POCT performance with increased operator training was demonstrated.ConclusionDifferent environments, patient populations, operator experience, laboratory access and practicalities associated with performing tests during mass influenza outbreaks may affect performance of influenza-specific laboratory tests.     

Laboratory test performance in young adults during influenza outbreaks at World Youth Day 2008

BackgroundThe performance of influenza laboratory diagnostics in young adults and in the setting of outbreaks during mass gatherings has not been well studied.ObjectivesWe compare the performance of point-of-care tests (POCTs) and immunofluorescence assays (IFAs) with nucleic acid tests (NATs) and viral culture in pilgrims attending influenza clinics established during a large influenza outbreak (World Youth Day, Sydney, Australia, 2008) to assess their performance under the real-life pressures of a mass influenza outbreak.Study designPatients with an influenza-like illness (ILI) underwent respiratory specimen sampling. Combined deep nares and throat swabs were collected for POCT by trained or untrained clinic staff; type-specific IFA; NAT and viral culture. Laboratory-confirmed influenza occurred if viral culture and/or NAT were positive; the performance of laboratory tests was calculated against this ‘gold standard’.ResultsA total of 230 samples were collected from 227 patients (median age, 20 years; interquartile range, 18–28 years), with 95 samples (41.3%) having laboratory-confirmed influenza infection (influenza A, 57; influenza B, 38). IFA and POCT sensitivities were 74.5% and 55%, respectively. Four of 51 (8%) culture-positive specimens were negative by NAT, and several errors in influenza virus typing occurred with IFA, POCT and NAT. A non-significant trend towards better POCT performance with increased operator training was demonstrated.ConclusionDifferent environments, patient populations, operator experience, laboratory access and practicalities associated with performing tests during mass influenza outbreaks may affect performance of influenza-specific laboratory tests.     

Improved detection of rhinoviruses in nasal and throat swabs by seminested RT-PCR

A seminested RT-PCR (nRT-PCR) was used to detect picornavirus (PV) RNA in cell cultures inoculated with rhinoviruses (HRVs) and enteroviruses (EVs). PCR tests in which a primary "touchdown" PCR was followed by secondary reactions using PV or HRV specific primers were able to differentiate HRVs of 48 serotypes from EVs. PVnRT-PCR and HRVnRT-PCR were then used to test nasal and throat swabs from adult subjects with naturally acquired respiratory virus infections. The swabs were also analysed for respiratory viruses by cell culture techniques and the rates of PV identification by the two methods were compared. PVnRT-PCR was found to be at least five times more sensitive than cell culture for the detection of PVs in these clinical specimens. Paired acute and convalescent serum samples were tested for complement fixing antibodies to adenovirus, influenza A and B, respiratory syncytial virus, parainfluenza viruses 1, 2, and 3, Myco plasma pneumoniae, and Chlamydia psittaci. An enzyme-linked immunosorbent assay (ELISA) was used to detect rises in antibody level to coronavirus types 229E and OC43. The overall rate of pathogen identification in 159 swabs from adult asthmatics increased from 28% when only cell culture and serology were used to 57% when these methods were supplemented by PVnRT-PCR. © 1993 Wiley-Liss, Inc.     

Influenza A/H5N1 virus infection in humans in Cambodia.

BACKGROUND: Between January 2005 and April 2006, six patients of influenza A/H5N1 virus infection were reported in Cambodia, all with fatal outcome. OBJECTIVES: We describe the virological findings of these six H5N1 patients in association with clinical and epidemiologic findings. STUDY DESIGN: Broncho-alveolar lavage, nasopharyngeal, throat and rectal swabs and sera were cultured for virus isolation and viral load quantified in clinical specimens by real-time RT-PCR. We compared sequences obtained from different body sites within the same patient to detect viral quasi-species. RESULTS: H5N1 virus strains isolated in Cambodia belong to genotype Z, clade 1 viruses. H5N1 viruses were isolated from serum and rectal swab specimens in two patients. The haemagglutinin gene sequences of the virus in different body sites did not differ. Amino acid substitutions known to be associated with a change in virus binding were not observed. CONCLUSION: The high frequency of virus isolation from serum and faecal swabs highlights that H5N1 is likely to be a disseminated infection in humans and this has implications for antiviral treatment, biosafety in clinical laboratories and on risks for nosocomial and human-to-human transmission. There were no tissue-specific adaptive mutations in the HA gene from viruses isolated from different organs.     

Evaluation of two rapid antigen assays, BioStar Strep A OIA and Pacific Biotech CARDS O.S., and culture for detection of group A streptococci in throat swabs.

Two rapid methods, BioStar Strep A OIA (OIA; BioStar, Inc., Boulder, Colo.), an optical immunoassay, and CARDS O.S. (O.S.; Pacific Biotech, Inc., San Diego, Calif.), a color immunochromographic assay, and two culture methods, one with 5% sheep blood agar (SBA) and one with Todd-Hewitt broth (TH; Remel, Lenexa, Kans.), were evaluated for use in the detection of Streptococcus pyogenes from pharnygeal swabs. Seven hundred forty-six double swabs (Culturette II) were processed, with OIA and SBA culture performed on one swab and O.S. and SBA culture performed on the other swab. The pledget from the Culturette II was incubated overnight in TH and was subcultured onto SBA for an additional 48 h in ambient air. All beta-hemolytic streptococci from culture were tested by a direct fluorescent-antibody test (Difco Laboratories, Detroit, Mich.). Specimens with discordant fluorescent-antibody test and rapid test results were also tested by using the Streptex latex agglutination reagent (Murex Diagnostics Limited, Dartford, England). The results obtained by all testing methods were compared with a combined test result ("gold standard"), which was defined as any positive culture detected by the SBA or TH culture methods and confirmed by Streptex latex agglutination or, in the case of negative results by both culture methods, a concomitant positive result by OIA and O.S. antigen testing. Sensitivity and specificity results for each of the methods were as follows, respectively: OIA, 81.0 and 97.5%; O.S., 74.4 and 99.0%; SBA culture, 92.3 and 98.3%; and TH culture, 86.4 and 100%. Both OIA and O.S. are suitable screening methods for detecting S. pyogenes directly from throat swabs but are of insufficient sensitivity to eliminate the need for backup cultures for specimens with negative OIA and O.S. results.