Controversies in viral diagnosis.

A number of fallacies concerning viral diagnosis persist. It is said that viral studies are useless since there is no treatment for viral diseases, but suitable therapies are available for a number of severe viral infections. Viral culture results are thought to be too slow to affect patient management, but the average time for detection of a virus is three to four days, and greater than 70% can be reported within five days; detection of viral antigen can be provided in hours. It is thought that viral infections are best diagnosed by serologic tests. However, serologic tests requiring demonstration of a rise in titer or seroconversion are inherently slower than cultures and therefore less useful. Genetic probes are insensitive compared with cultures, and enzyme-linked immunosorbent assay methods for detecting viral antigen are no more sensitive than fluorescent antibody techniques and do not provide a means of assaying the quality of the sample. Finally, it is often stated that viral studies should be performed only in reference or regional laboratories. Regional virus laboratories should be located in teaching hospitals, and networks should be established to permit hospital laboratories to be involved at different levels.