Comparison of the NOW Influenza A & B, NOW Flu A, NOW Flu B, and Directigen Flu A+B assays, and immunofluorescence with viral culture for the detection of influenza A and B viruses.

To evaluate the Binax NOW Influenza A & B combination assay, we tested upper respiratory tract samples in parallel with the Binax NOW Flu A and Binax NOW Flu B assays, the Becton-Dickinson Directigen Flu A+B assay, and immunofluorescence, and the results were compared with viral culture. Of the 521 samples tested, influenza A was cultured from 113 and influenza B from 6. There were no significant differences in the performance of all rapid antigen tests, with sensitivities of 53% to 59% for detecting influenza A compared with culture and immunofluorescence (80%). The sensitivities for all rapid tests were significantly higher for nasopharyngeal samples than for throat swabs. The Binax NOW Influenza A & B assay performed as well as other rapid assays. Commercial antigen detection assays are useful tools for the rapid diagnosis of influenza; however, confirmatory testing is always recommended. The use of nasopharyngeal samples for all rapid detection methods should be strongly encouraged.

Viral etiology of acute respiratory tract infections in children presenting to hospital: role of polymerase chain reaction and demonstration of multiple infections.

BACKGROUND: Viral lower respiratory tract infections are a leading cause of hospitalization for young children. METHODS: We used polymerase chain reaction (PCR) and conventional methods of cell culture and antigen detection to establish the viral etiology of acute respiratory tract infections in 75 hospitalized children. RESULTS: One or more viral pathogens were detected in 65 (87%) children, with respiratory syncytial virus being the most commonly identified virus (36 children). Other viruses identified included influenza virus types A and B, parainfluenzavirus type 3, adenovirus, enterovirus, rhinovirus, coronavirus and human metapneumovirus. PCR increased the diagnostic yield significantly compared with antigen detection and culture, with 39 (21%) diagnoses identified by this method. Multiple infections were identified in 20 (27%) children. CONCLUSIONS: PCR-based methodologies offer increased sensitivity for the detection of most respiratory viruses in young children. The inclusion of PCR into diagnostic testing strategies is needed to broaden our understanding of the natural ecology of respiratory viruses and the significance of multiple infections.

Failure to genotype herpes simplex virus by real-time PCR assay and melting curve analysis due to sequence variation within probe binding sites.

Real-time PCR with melting curve analysis of PCR products is a rapid procedure for detecting and genotyping herpes simplex virus (HSV). When testing mucocutaneous samples for HSV by a real-time PCR assay targeting the DNA polymerase gene, we found that some PCR products had atypical melting curves that did not conform to the expected melting temperatures for HSV type 1 or 2. Sequence analysis showed that these strains had base-pair mismatches over the probe binding sites. An alternative assay is required to type such atypical isolates.

Evaluation of a PCR assay for detection of Streptococcus pneumoniae in respiratory and nonrespiratory samples from adults with community-acquired pneumonia.

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia, but it is undoubtedly underdiagnosed. We used a nested PCR assay (targeting the pneumolysin gene) to detect S. pneumoniae DNA in multiple sample types from 474 adults with community-acquired pneumonia and 183 control patients who did not have pneumonia. Plasma or buffy coat samples were PCR positive in only 6 of the 21 patients with positive blood cultures for S. pneumoniae and in 12 other patients (4 of whom had no other laboratory evidence of S. pneumoniae infection). Buffy coat samples from two control patients (neither having evidence of S. pneumoniae infection), but no control plasma samples, were PCR positive. Although pneumococcal antigen was detected in the urine from 120 of 420 (29%) patients, only 4 of 227 (2%) urine samples tested were PCR positive. Overall, 256 of 318 (81%) patients had PCR-positive sputum samples, including 58 of 59 samples from which S. pneumoniae was cultured. Throat swab samples from 229 of 417 (55%) patients were PCR positive and, in those who produced sputum, 96% also had positive PCR results from sputum. Throat swabs from 73 of 126 (58%) control patients were also PCR positive. We conclude that the pneumolysin PCR assay adds little to existing diagnostic tests for S. pneumoniae and is unable to distinguish colonization from infection when respiratory samples are tested.