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Base RSV Diagnosis on Exam, History, and Season; Tests Mislead


 

LAS VEGAS — Respiratory syncytial virus infection is a clinical diagnosis based on patient history, physical exam, and the season of the year, Dr. Veda L. Ackerman said at a meeting sponsored by the American Academy of Pediatrics' California Chapters 1, 2, 3, and 4 and the AAP.

“So if you try to tell me that you have a baby who is RSV positive on July 4th in your practice, I'm going to tell you that your RSV test has cross-reacted with another virus,” said Dr. Ackerman, of the section of pulmonology and critical care in the department of pediatrics at the James Whitcomb Riley Hospital for Children, Indianapolis. “We do not see RSV in the summer in the United States. It peaks in mid-winter and early spring.”

You can use RSV rapid tests to make a diagnosis, but these “have both a high degree of false-negatives and a high degree of false-positives,” she said. “You have to take that into consideration.”

Even with viral cultures— which are traditionally the preferred method—there is a high false-negative rate due to the lability of the virus. “So you can't take RSV positive or negative as a very good guideline for what you do,” she explained. “As therapy is largely supportive, proving that the baby has RSV really shouldn't matter to you, except for potential infection control.”

By age 2 years, 99% of children have been infected with RSV at least once and 36% have had a least 2 infections. This makes RSV “as contagious as varicella, and it has significant impact on missed days of school and missed days of work.”

Factors that increase one's risk of acquiring RSV infection include maternal education of grade 12 or less, day care attendance, school-age siblings, lack of breast-feeding, two or more people sharing a bedroom, multiple births, passive smoke exposure, and birth within 6 months before onset of RSV infection.

“Obviously you're much better delivering your baby in March or April than you are in December,” Dr. Ackerman said. “You're less likely to have that baby acquire RSV.”

Clinical features of RSV infection include nasal flaring; chest wall retractions; tachypnea with apneic episodes; expiratory wheezing; prolonged expiration; rales and rhonchi; croupy cough; and hypoxemia and cyanosis. Tiny babies infected with RSV may present only with apnea.

In a study of 213 infants younger than 13 months who had bronchiolitis, the best predictor of more severe disease was an oxygen saturation level of less than 95% oximetry (Am. J. Dis. Child. 1991;145:151–5).

“If you happen to not have [pulse] oximetry in your office, I urge you that it is one of the things that will help you tremendously, both in figuring out what to do with the child with asthma and what to do with the child with bronchiolitis,” Dr. Ackerman said.

Treatment for RSV infection is mainly supportive and includes supplemental humidified oxygen, IV hydration if needed, proper nutrition, and ventilatory assistance for respiratory failure.

A trail of bronchodilators is appropriate, “but to continue them if there's no response is not appropriate,” she warned.

Corticosteroids are not currently indicated for RSV infection but Dr. Ackerman said she would use them in a 9-month-old infant with a second or third episode of wheezing who happens to have RSV. “That's an asthmatic and that's a baby [in whom] I would use corticosteroids.”

She also would use them in a baby with RSV and heart failure.

Efforts to delay RSV spread include limiting contact with infected people, enrolling your child in a day care facility with few children, and washing hands frequently.

The James Whitcomb Riley Hospital for Children is in the midst of a handwashing campaign. Parents are given a brochure on admission which urges them to ask, “Doctor, have you washed your hands?” every time they see a physician touch their child. “My answer is supposed to be, 'Yes, I have. Thank you for asking,'” she said.

Other efforts to prevent spread include disinfecting surfaces exposed to infectious secretions, grouping hospitalized patients with RSV, and promoting breast-feeding.

One strategy to prevent infection in high-risk premature infants is to administer palivizumab (Synagis), which has been shown to reduce RSV-related hospitalizations in this patient population by more than 50%. “The down side of Synagis is you have to give it before exposure and you have to give it every 30 days,” Dr. Ackerman commented. “This is really a problem because you have to give it before you're ever exposed and you have to give it frequently.”

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