Vidyya Medical News Service
Volume 6 Issue 336 Published - 14:00 UTC 08:00 EST 1-Dec-2004 Next Update - 14:00 UTC 08:00 EST 2-Dec-2004
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Improving diagnosis by molecular methods for difficult viral infections

In a study of 148 bronchoalveolar lavage (BAL) specimens collected by analysis from patients with suspected hard-to-detect acute respiratory infections, only about 1 in 3 cases that were identified as virus positive by molecular methods were also revealed through conventional cell culture analysis.

The investigators analyzed the specimens for the presence of 11 different viruses, as well as several types of pneumonia, plus Legionnaire's Disease. Respiratory viruses were identified in 34 of 117 BAL specimens (29 percent) obtained in patients with suspected respiratory infection and in only 2 of 31 control patients without respiratory symptoms.

The researchers used reverse transcription chain-reaction assay for their analysis. According to the authors, viruses in the lower respiratory tract are a leading cause of disease, hospitalization, and antibiotic use in patients with immunosuppressive and/or chronic lung diseases.

However, in 70 to 80 percent of the cases, the identity of the virus remains undetermined. (To collect BAL specimens, doctors wedge a bronchoscope into a small airway in the lung, and then instill saline solution through the instrument. The fluid is then suctioned back through the scope, bringing back cellular material for analysis.) The investigators said that their sensitive molecular tool better estimated the frequency of respiratory viral infection in hospitalized patients and permitted the identification of the cause of a respiratory event in patients who did not respond to conventional empirical antibiotic treatment.

The study can be found in the first issue for December 2004 of the American Journal of Respiratory and Critical Care Medicine.

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