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.

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.

Treatment & Management

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Media Gallery

Respiratory syncytial virus infection season, United States, by region and Florida. Image courtesy of Centers for Disease Control and Prevention.
Electron micrograph of respiratory syncytial virus (RSV). RSV is most common cause of bronchiolitis and pneumonia in children younger than 1 year. Image courtesy of Centers for Disease Control and Prevention.

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Author

Leonard R Krilov, MD Chief of Pediatric Infectious Diseases and International Adoption, Vice Chair, Department of Pediatrics, Winthrop University Hospital; Professor of Pediatrics, Stony Brook University School of Medicine

Leonard R Krilov, MD is a member of the following medical societies: American Academy of Pediatrics, American Pediatric Society, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Society for Pediatric Research

Disclosure: Nothing to disclose.

Coauthor(s)

Asif Noor, MD Assistant Professor of Pediatric Infectious Diseases, NYU Long Island School of Medicine

Asif Noor, MD is a member of the following medical societies: American Academy of Pediatrics, Pediatric Infectious Diseases Society

Disclosure: Nothing to disclose.

Chief Editor

Russell W Steele, MD Clinical Professor, Tulane University School of Medicine; Staff Physician, Ochsner Clinic Foundation

Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, Southern Medical Association

Disclosure: Nothing to disclose.

Acknowledgements

Ashir Kumar, MD, MB Professor Emeritus, Department of Pediatrics and Human Development, Michigan State University College of Human Medicine

Ashir Kumar, MD, MB is a member of the following medical societies: American Association of Physicians of Indian Origin and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Larry I Lutwick, MD Professor of Medicine, State University of New York Downstate Medical School; Director, Infectious Diseases, Veterans Affairs New York Harbor Health Care System, Brooklyn Campus

Larry I Lutwick, MD is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.