Respiratory Syncytial Virus Infection Workup

Updated: Nov 06, 2023
  • Author: Leonard R Krilov, MD; Chief Editor: Russell W Steele, MD  more...
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Laboratory Studies

Laboratory studies generally are not indicated in the infant with bronchiolitis who is comfortable in room air, well hydrated, and feeding adequately.

Nonspecific laboratory studies may include a complete blood count (CBC), assessment of serum electrolyte concentrations, urinalysis, and measurement of oxygen saturation. The CBC may reveal a normal or mildly elevated white blood cell (WBC) count and an elevated percentage of band forms. Blood cultures, although frequently obtained, are rarely positive for pathogenic bacteria. Arterial blood gas analysis may be indicated if carbon dioxide retention is a concern.

Specific diagnostic tests for confirmation of respiratory syncytial virus (RSV) infection are readily available. These tests can be performed on samples of secretions obtained by washing, suctioning, or swabbing the nasopharynx. Secretions can be analyzed for virus in the laboratory by means of culture, antigen-revealing techniques, or polymerase chain reaction (PCR). Molecular probes for revealing RSV in clinical specimens may be more sensitive than the aforementioned assays and are becoming clinically available, but they presently are more expensive. There are 6 commercially available multiplex PCR assays (nested PCR), with sensitivity and specificity of 100% and 89% respectively with some variability in performance.

The antigen detection methods offer the potential for diagnosis within hours and may be obtained reliably in the absence of a sophisticated virology laboratory. However, monitoring of test performance is critical for maintaining appropriate sensitivity and specificity. Specific tests for RSV may be indicated for therapeutic decision making (eg, withdrawal of unnecessary antibiotics), isolation of patients, and educating parents and staff about the nature of RSV disease.


Other Studies

Chest radiography

Chest radiography is frequently obtained in children with severe RSV infection. Typically, it reveals hyperinflated lung fields with a diffuse increase in interstitial markings. In 20-25% of cases, focal areas of atelectasis or pulmonary infiltrates are also noted. Generally, these findings are neither specific to RSV infection nor predictive of the course or outcome, except for the observation that infants who have the additional findings of atelectasis or pneumonia may have a more severe disease course.

Histologic findings

In infants who have died of RSV bronchiolitis, histologic study of lung tissue demonstrates mononuclear cell and neutrophil infiltration of the peribronchiolar areas, necrosis of the small airway epithelium, plugging of the lumens with exudate and edema, and atelectasis and hyperinflation.