Comparison of a new commercial enzyme immunoassay for rapid detection of respiratory syncytial virus

Two rapid methods for detection of respiratory syncytial virus in respiratory specimens were compared: direct immunofluorescence assay (DFA) with monoclonal antibody and an enzyme immunoassay (EIA) (Test-Pack RSV). Ninety-five nasopharyngeal washings and aspirates from 51 children were examined; the patients were hospitalized during a winter outbreak of RSV infection in the first trimester of 1990. A total of 41.0 % and 56.8 % of these samples were positive by EIA and DFA respectively. Considering only the 51 specimens collected at the onset of illness, EIA detected 72.5 % positive samples and DFA detected 78.4 %. In comparison with DFA, EIA was 92.5 % sensitive and 100 % specific for the acute phase of illness. When all the samples were taken into account, specificity was maintained but sensitivity fell to 72.2 %. The results show that both methods are useful during the acute phase of the illness, when the viral load is important. However, later on in the course of the infection DFA appears to be more sensitive than EIA.     

Evaluation of an enzyme membrane immunoassay (Directigen RSV) for the rapid diagnosis of respiratory syncytial virus infections

A rapid enzyme immunoassay (EIA) membrane test, the Directigen respiratory syncytial virus (Becton Dickinson), was compared with cell culture, an indirect immunofluorescence (IF) test, the Monofluokit respiratory syncytial virus (Diagnostics Pasteur), and a conventional enzyme immunoassay antigen test, the Abbott respiratory syncytial virus enzyme immunoassay in nasal aspirates specimens from children with suspected respiratory syncytial virus (RSV) bronchiolitis. The sensibility and specificity of the Directigen, respiratory syncytial virus were 91% and 98% respectively, as compared with those of culture, and of 93% and 86% as compared with the Monofluokit respiratory syncytial virus. In the comparison of the two enzyme immunoassays, Directigen respiratory syncytial virus detected more positive specimens: 68/127 than the other: 46/127. Directigen respiratory syncytial virus is a very rapid test, (15-min), sensitive and specific, which can be used as an alternative technique for detection of respiratory syncytial virus in nasal samples when viral isolation or immunofluorescence direct are not available.     

Evaluation of the 3M rapid detection test for respiratory syncytial virus (RSV) in children during the early stages of the 2009 RSV season

We report the results of the 3M rapid detection respiratory syncytial virus (RSV) assay. This study includes pediatric patient results from nasopharyngeal swabs submitted from October to December 2009. There was a sensitivity of 74% and specificity approaching 100% compared to the PCR-based xTAG respiratory viral panel.     

Evaluation of the Abbott TESTPACK RSV enzyme immunoassay for detection of respiratory syncytial virus in nasopharyngeal swab specimens.

The Abbott TESTPACK RSV assay (Abbott Laboratories, North Chicago, Ill.), a rapid (20-min) enzyme immunoassay, was compared with culture and direct immunofluorescence (DFA) of nasopharyngeal cells for the detection of respiratory syncytial virus (RSV) in nasopharyngeal swab specimens. Nasopharyngeal swab specimens, collected from 234 infants, were placed in viral transport medium. Portions of specimen in transport medium were used for each test. Of 234 specimens, 70 (30%) were culture positive, 103 (44%) were DFA positive, 107 (46%) were culture or DFA positive, and 112 (48%) were TESTPACK RSV positive. Of 19 specimens positive by TESTPACK RSV but negative by culture or DFA, 15 were positive by the blocking assay. A total of 122 specimens were culture, DFA, or blocking assay positive; TESTPACK RSV detected 108 specimens (sensitivity, 89%). The specificity, positive predictive value, and negative predictive value of TESTPACK RSV as compared with those of culture, DFA, and the blocking assay were 96, 96, and 89%, respectively. By comparison, the sensitivity, specificity, positive predictive value, and negative predictive value of combined culture and DFA were 88, 100, 100, and 88%, respectively. TESTPACK RSV is a rapid and reliable enzyme immunoassay for the direct detection of RSV antigen in nasopharyngeal swab specimens.     

A rapid test for detection of respiratory syncytial virus in nasopharyngeal secretion

A new rapid membrane enzyme immunoassay (MEIA; Directigen RSV) for detection of respiratory syncytial virus (RSV) was evaluated using samples of nasopharyngeal secretion from infants and children with acute respiratory disease. The MEIA was compared with an immunofluorescent antibody (IF) technique using a sensitive biotin-avidin (BA) EIA as reference. Of 242 samples tested, 108 were positive by the MEIA and 123 by the BA-EIA. Of 144 samples which were also tested by the IF technique, 57 were positive by the BA-EIA and 43 by the IF technique. These results give a sensitivity of 86 % and 72 % for the MEIA and IF technique respectively. Of 57 samples found to be positive by the BA-EIA, 41 were positive by the IF technique, but 48 were positive by the MEIA. The MEIA is thus more sensitive than the IF technique but less sensitive than the BA-EIA in detecting RSV in nasopharyngeal secretions.     

Diagnostic efficacy of two rapid tests for detection of respiratory syncytial virus antigen.

With the availability of ribavirin therapy for serious respiratory syncytial virus (RSV) infections, rapid diagnostic tests for the detection of RSV antigen are increasingly important. Efficacies of a commercially available enzyme immunoassay (EIA) (Abbott Laboratories, North Chicago, Ill.) and a fluorescent-antibody assay (FA) were evaluated in a study involving 135 specimens from children with respiratory symptoms. A nasal wash specimen was cultured immediately on RSV-sensitive A549 cells; the nasal wash was also used for EIA. FA was performed on a nasopharyngeal swab specimen with bovine anti-RSV and anti-bovine immunoglobulin G antisera (Burroughs Wellcome Co., Research Triangle Park, N.C.). A total of 39 specimens (28%) were tissue culture positive, including 35 EIA-positive and 37 FA-positive samples (sensitivities, 90 and 95%, respectively). All 96 tissue culture-negative specimens were EIA negative (specificity, 100%); 94 of these 96 specimens were FA negative (specificity, 98%). Positive and negative predictive values for the tests were as follows: 100 and 96% for EIA, respectively, and 95 and 98% for FA, respectively. Other viruses, including influenza A virus, adenovirus, enterovirus, and herpes simplex virus, were isolated in nine cases. One adenovirus-positive specimen had a false-positive RSV FA result; all nine specimens were RSV EIA negative. Both tests performed well in our study and provide cost-effective alternatives to tissue culture. The RSV EIA, in particular, uses standard serologic techniques and equipment and does not require expertise in virology. More widespread availability of rapid diagnostic tests for RSV will hopefully result in early and appropriate use of antiviral therapy in patients at risk for serious RSV infections.     

Performance characteristics of VIDAS and directigen respiratory syncytial virus (RSV) antigen detection assays and culture for the identification of RSV in respiratory specimens

In a comparison of the Directigen and VIDAS respiratory syncytial virus antigen detection assays with viral culture, the sensitivity, specificity, positive and negative predictive values, and testing efficiency were 86, 93.1, 82.7, 94.6, and 91.2% for Directigen; 96.1, 90.8, 80.3, 98.3, and 92.3% for VIDAS; and 88.2, 100, 100, 95.7, and 96.8% for viral culture, respectively.     

Evaluation of a new rapid test for the combined detection of hepatitis B virus surface antigen and hepatitis B virus e antigen

There are about 350 million chronic hepatitis B virus (HBV) carriers worldwide. A proactive approach to the management of this disease is likely to reduce the morbidity and mortality caused by HBV. This study aimed to evaluate the diagnostic performance of a novel tool for discriminating between infected and noninfected subjects, the hepatitis B sAg/eAg test (Binax Inc., Portland, Maine). The test is designed to rapidly and accurately detect both the HBV surface antigen (HBsAg) and the HBV e antigen (HBeAg). A cohort of 942 subjects was tested. The serum clinical sensitivity of the hepatitis B sAg/eAg test was 99.75 and 96.37% for HBsAg and HBeAg, respectively. Serum clinical specificity was 99.32% for HBsAg and 98.99% for HBeAg. Analytical sensitivity was satisfactory for the purposes of population screening. Visual evaluation showed that the test signals were stable for at least 3 h after the recommended evaluation time. No interference or cross-reactivity was observed with known interfering substances and virologic markers. These results indicate that the hepatitis B sAg/eAg test is well suited to the accurate detection of HBV carriers. In addition to the good clinical specificity and sensitivity of this test, its stability and user-friendly design mean that a correct performance, even under field conditions, is highly likely. Consequently, the hepatitis B sAg/eAg test has the potential to identify subjects who require HBV vaccination (HBsAg(-) and HBeAg(-)) and HBV-infected individuals who might benefit most from antiviral therapy (HBsAg(+) and HBeAg(+)).     

Evaluation of a visual, rapid, membrane enzyme immunoassay for the detection of herpes simplex virus antigen.

We evaluated a 12-min, direct, monoclonal antibody-based enzyme immunoassay (EIA) (SureCell; Kodak, Rochester, N.Y.) which aids in the detection of herpes simplex virus infection; the assay system is also approved for culture confirmation. The test was evaluated from direct clinical samples and compared with conventional culture methodology by using a single swab. A total of 265 specimens from 180 female cervical-urogenital sites, 62 male urogenital sites, 4 rectal sites, 3 skin sites, 6 oral sites, and 10 colposcopy sites were collected on Dacron or cotton swabs and placed in viral transport medium (VTM). Within 6 h of receipt, 0.2 ml of the vortexed VTM was inoculated into each of two replicate cell cultures. Cell monolayers were observed daily for ten days, and cytopathic effect was confirmed by using an indirect immunoperoxidase reagent. The procedure for the SureCell assay conformed to the manufacturer's recommendations. When conventional culture was compared with EIA results, the overall sensitivity, specificity, positive predictive value, negative predictive value, and agreement were 64.4, 98.9, 96.7, 84.4, and 87.2%, respectively. Variables affecting the EIA sensitivity are the stage of the lesion and conventional culture methodologies. A review of culture results for 32 EIA false-negative tests indicated that 15 were detected after 48 h of incubation. Cytopathic effect observed at 48-, 72-, and 96-h cutoffs altered the sensitivity for the EIA. To ensure detection of SureCell herpes simplex virus-negative specimens, it is recommended that an unused aliquot of VTM be tested in cell culture.     

Evaluation of the cholera spot test: a chromatographic immunoassay for the rapid detection of cholera antigen

A chromatographic immunoassay cholera antigen detection kit, the Cholera Spot test, was evaluated. The test was found to be specific with a sensitivity of 10(6) cfu/ml for the direct detection of V. cholerae in simulated stool specimens and 10 cfu/ml in simulated cotton-tipped swab specimens after overnight incubation in alkaline peptone water. This enables early recognition of cholera cases and their contacts so that prevention and control measures can be promptly instituted.     

Antibiotic use in children is not influenced by the result of rapid antigen detection test for the respiratory syncytial virus.

BACKGROUND: Rapid antigen detection test (RADT) for respiratory syncytial virus (RSV) is widely used in children hospitalized with acute respiratory tract infection (ARTI), but its influence on antibiotic (AB) use is uncertain. OBJECTIVE: To evaluate if confirmation of RSV infection by RADT modified AB use and elucidate others factors associated with the continuation of antibiotics. STUDY DESIGN: Charts of children hospitalized with viral ARTI aged 0-35 months were reviewed. Modification of antibiotics according to RSV RADT results was compared using Kaplan-Meier estimates and multivariate Cox regression. RESULTS: Of children receiving antibiotics when the RSV RADT result was available, RSV RADT was positive in 144 and negative in 54. Positive RSV RADT results did not lead to modification of antibiotic use. Factors independently associated with cessation of intravenous antibiotics were age > or = 3 months (HR 2.44 [1.41-4.21]) and absence of pneumonia (HR 1.50 [1.03-2.19]). Absence of otitis was associated with cessation of oral antibiotics (HR 9.16 [95% CI, 2.35-35.76]). CONCLUSION: Confirmed presence of RSV by RADT did not influence antibiotic use in young children with ARTI. Except with pneumonia, the risk of bacterial superinfection of RSV infected children is minimal and confirmation of RSV infection should prompt treating physicians to interrupt antibiotics.     

Reliability of two new test kits for rapid diagnosis of respiratory syncytial virus infection.

Two new rapid enzyme immunoassays (EIAs) for detecting respiratory syncytial virus (RSV), Directigen (Becton Dickinson Microbiology Systems) and TestPack (Abbott Diagnostics) were compared with virus isolation and direct immunofluorescence by using fresh specimens. The sensitivities of both EIAs were low (72 to 73%), but when initial specimens were used, TestPack had a high sensitivity (92%) in contrast to that of Directigen (76%). Because of its high sensitivity and specificity, TestPack can be used for diagnosis of RSV in acute disease.     

Microneutralization test for respiratory syncytial virus based on an enzyme immunoassay.

Virus infectivity and antibody neutralization titers for respiratory syncytial virus were determined in cell cultures in microtiter plates. After an appropriate incubation period, the cells were fixed, and an enzyme-linked immunosorbent assay was performed directly in the microtiter plates for detection of virus. Results could be read and recorded automatically, which is especially helpful when running large numbers of tests.     

Evaluation of three rapid enzyme immunoassays and cell culture for detection of respiratory syncytial virus

Three rapid enzyme immunoassay techniques for the detection of respiratory syncytial virus antigen (Becton Dickinson Directigen RSV, Abbott RSV Testpack and Abbott RSV EIA) and cell culture were evaluated in a total of 250 nasal washings. The sensitivity and specificity were 62 % and 76 % respectively for Directigen, 64 % and 86 % for RSV Testpack, and 76 % and 81 % for RSV EIA, taking cell culture as the reference method. Agreement between cell culture and EIA techniques was 79 % (70 positive and 128 negative results). All three EIA techniques gave positive results in 69 samples (52 positive and 17 negative in the cell culture). In 121 samples all three EIA techniques gave negative results (103 negative and 18 positive in the cell culture). Using the cell culture technique 46 strains other than respiratory syncytial virus were isolated.     

Comparison of two rapid methods for detection of respiratory syncytial virus (RSV) (Testpack RSV and ortho RSV ELISA) with direct immunofluorescence and virus isolation for the diagnosis of pediatric RSV infection.

The ability of two commercial immunoassays to detect respiratory syncytial virus (RSV) in respiratory specimens was evaluated as follows: 152 specimens were tested by TestPack RSV (Abbott), and 72 were tested by Ortho RSV ELISA (Ortho). Test outcomes were compared with those of virus isolation alone, direct immunofluorescence assay (DFA) alone, or virus isolation and/or DFA. TestPack RSV versus virus isolation showed 91% sensitivity, 96% specificity, 93% positive predictive value (PPV), and 95% negative predictive value (NPV). TestPack RSV versus DFA showed 89% sensitivity, 97% specificity, 96% PPV, and 93% NPV. When TestPack RSV performance was compared with that of virus isolation and DFA, the sensitivity was 87% and the specificity was 100%. Ortho RSV ELISA versus virus isolation showed 88% sensitivity, 87% specificity, 79% PPV, and 93% NPV. Ortho RSV ELISA versus DFA showed 91% sensitivity, 88% specificity, 81% PPV and 95% NPV. When Ortho RSV ELISA performance was compared with that of virus isolation and DFA, the sensitivity was 86%, the specificity was 89%, the PPV was 86%, and the NPV was 89%. The accuracy of the TestPack RSV in combination with ease of performance and no need for specialized equipment or special skills make it an attractive alternative to DFA for rapid direct detection of RSV.     

Dual-enzyme cascade-magnetic separation immunoassay for respiratory syncytial virus

A new immunoassay developed for the detection of respiratory syncytial virus (RSV) makes use of magnetic separation and amplification by a dual-enzyme cascade for signal generation. Magnetic particles are conjugated to monoclonal anti-RSV antibodies through the heterobifunctional crosslinker sulfosuccinimidyl 4-(maleimidomethyl)cyclohexane-1-carboxylate, yielding particles of high specific activity and low background. The dual-enzyme cascade is initiated by activation of a masked inhibitor for the enzyme rabbit liver esterase (RLE) by an alkaline phosphatase-antibody conjugate. The esterase activity is then measured to determine the degree of inhibition and, hence, the amount of specifically labeled antigen. These methods yield an immunoassay which is rapid and sensitive. Formation of the immunometric complex requires only 7 min and the total assay time is 40 min. The limit of detection for RSV fusion protein was found to be 1 ng or 10(-14) mol per test. Pre-clinical evaluation of the assay with 52 clinical specimens (nasal washes or aspirates) gave 96% sensitivity (25/26) and 96% specificity (25/26) with respect to a microtiter ELISA procedure and blocking antibody assay.     

Prospective evaluation of a dot-blot enzyme immunoassay (Directigen RSV) for the antigenic detection of respiratory syncytial virus from nasopharyngeal aspirates of paediatric patients

This study investigated the efficacy of a commercial enzyme immunoassay (Directigen RSV, ColorPAC) in comparison with the shell vial culture method (using Hep-2 cells) for the detection of respiratory syncytial virus (RSV) in nasopharyngeal aspirates from children with bronchiolitis. During the period 1995-2002, 4950 samples were examined. RSV was detected in 1660 (33.5%) samples, with a sensitivity of 80.9%, a specificity of 97.5%, a positive predictive value of 93.8%, a negative predictive value of 91.6%, and a testing efficiency value of 92.2% compared with shell vial culture. In 83 (5%) samples, the ColorPAC was positive and the shell vial assay was negative. Of these, 71 (85.6%) were false-negative by cell culture. The true false-positive results obtained by ColorPAC represented only 0.7% of all RSV-positive samples. In general, no statistically significant differences were detected between the different months and epidemic periods studied. Compared with ColorPAC, the shell vial culture method displayed a sensitivity of 95.8% and a specificity of 100%. Overall, the ColorPAC assay was an acceptable, simple and rapid method for the antigenic detection of RSV in paediatric respiratory samples.     

Evaluation of five methods for respiratory syncytial virus detection.

A total of 117 nasal aspirates were cultured for respiratory syncytial virus (RSV) and tested for RSV antigen by a direct fluorescent-antibody (DFA) test (Bartels Immunodiagnostic Supplies, Inc., Bellevue, Wash.), the Directigen enzyme immunoassay (EIA; Becton Dickinson Microbiology Systems, Cockeysville, Md.), the TestPack EIA (Abbott Laboratories, North Chicago, Ill.), and RSV EIA (Abbott). Agreement of two of five methods or a positive RSV culture were required to validate a result. A total of 57 of 117 (48.7%) specimens were culture positive in HEp-2 cells, A549 cells, or both. A total of 5 of 117 (4.3%) additional specimens met the criteria of a positive specimen; i.e., 62 of 117 (53.0%) specimens were positive. Results obtained from 77 of 117 (65.8%) specimens were concordant for all five methods. The sensitivities, specificities, and positive and negative predictive values for the culture and DFA methods were 91.9, 100, 100, and 91.7% and 91.9, 96.4, 96.6, and 91.4%, respectively. The sensitivities, specificities, and positive and negative predictive values for the three EIA procedures, Directigen, TestPack, and RSV EIA, were 75.8, 80.0, 81.0, and 74.6%; 93.6, 100, 100, and 93.2%; and 71.0, 100, 100, and 75.3%, respectively. New self-contained EIA configurations and the DFA method offer attractive alternatives to the culture method. Technical simplicity, rapid turnaround time, performance, and cost must all be considered when selecting a system for RSV detection.