Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1410 page)

   
Positive:
Because common causes of pararespiratory infections are usually derived from upper respiratory tract endogenous flora, positive culture must be interpreted in the context of quantity or bacterial growth, purity of culture, Gram stain findings, and clinical signs and symptoms.

   Limitations

   
Common pitfall:
Noninvasively collected specimens, which are more likely to represent endogenous rather than pathogenic flora, are often submitted for patient evaluation.

RESPIRATORY CULTURE, RULE OUT VIRAL PATHOGENS

   Definition

   Most respiratory viral syndromes are relatively mild and self-limited. Occasionally, severe disease develops for which specific diagnosis is needed to optimize therapeutic and management decisions. Viral culture may be used to provide isolates for antiviral susceptibility testing or further characterization for epidemiologic reasons. This test may be ordered to make a specific diagnosis for severe seasonal respiratory viral illness. Agents cultured typically include influenza virus A and B, RSV, and parainfluenza virus types 1, 2, and 3; adenovirus may be included.

   Special Collection and Transport Instructions

   Specimens should be collected according to general recommendations for virus culture of the specimen type.

   Specimens should be collected early in acute infection.

   Nasopharyngeal specimens are often optimal for diagnosis.

   RSV is a fastidious virus and should be delivered to the laboratory as quickly as possible. This virus may not survive freezing if prolonged transport is needed. Most specimens should be placed in a viral transport medium and transported on wet ice (4°C).

   Specimens for molecular diagnostic, DFA, EIA, or other diagnostic testing for respiratory viruses should be submitted according to laboratory recommendations.

   Use

   Method: