Rapid diagnostic testing for the identification of respiratory agents in the emergency department

Pneumonia, influenza, and respiratory syncytial virus (RSV) are common causes of illness in children presenting to an emergency department of clinic. Rapid tests to aid in their diagnosis are available. Sputum gram stain can be helpful in selected patients with pneumonia. Assays based on enzyme immunoassay are available for influenza and RSV and are quite sensitive. However, there are problems with using these assays on a routine basis in the outpatient setting. Physicians should be aware of how the frequency of a disease affects the predictive value of a diagnostic assay. If specific therapy for the infection is not available or is not indicated, a specific diagnosis is generally not required. Routine testing for influenza and RSV may be helpful in inpatients and in selected high-risk outpatients, but is otherwise of limited value.