Risk Factors Outside Of AAP Guidelines Identify More Preemies Needing RSV Prophylaxis

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Main Category: Pediatrics / Children's Health
Also Included In: Infectious Diseases / Bacteria / Viruses;  Respiratory / Asthma
Article Date: 11 Oct 2008 - 3:00 PST

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New data have emerged regarding three risk factors which may help pediatricians better identify which preterm infants are at high risk of severe respiratory syncytial virus (RSV) disease and may thus benefit from palivizumab (Synagis®) prophylaxis, investigators reported at the American Academy of Pediatrics (AAP) 2008 National Conference and Exhibition.

The risk factors include cigarette smoking, crowded living conditions, and young chronologic age.

"We believe that adding these risk factors for RSV prophylaxis to the list currently recommended by the AAP will allow pediatricians to target a subset of high-risk, preterm infants who might otherwise be missed," principal investigator Doris Makari, M.D., Senior Director of Medical Affairs at MedImmune, LLC. in Gaithersburg, Maryland, commented.

Preterm infants born at 32 to 35 weeks gestational age (GA), who represent the majority of the preterm population, have a significantly higher risk of severe RSV disease than full-term infants, she said.

In 2003, the AAP released guidelines that recommend the use of palivizumab in high-risk infants 32 to 35 weeks GA who are younger than six months of age at the start of RSV season, provided they have at least two of the following risk factors: attendance in day care, school-age siblings, exposure to environmental pollutants ( excluding tobacco smoke ), congenital airway anomalies, and severe neuromuscular disease.

However, new data regarding additional risk factors for RSV hospitalization have since been published, including infant exposure to any tobacco smoke, four or more individuals residing in a single home, and age younger than three months at the start of the RSV season or being born during the RSV season.

Palivizumab, a humanized monoclonal antibody, has been shown to reduce hospitalization due to RSV by 80% in infants 32 to 35 weeks GA.

Dr. Makari's study reviewed 3,876 medical records of infants 32 to 35 weeks GA born between 4/1/05 and 11/30/06. The records had been maintained by 382 pediatricians throughout the U.S.

Hospitalization for RSV was confirmed through RSV-specific ICD-9 code or microbiological confirmation of RSV during hospitalization for unspecified bronchiolitis.

1967 infants did not receive prophylaxis. In 528/1967 (27%) infants, palivizumab prophylaxis was requested by the treating physician but was not authorized. The most common reason for refusal was payer denial.

Overall, RSV hospitalization occurred in 44 (8.3%) of the 528 infants in whom palivizumab prophylaxis had been requested but denied compared with 42 (2.9%) of 1,429 infants in whom the drug had not been requested, respectively, p less than 0.01.

The requirement by AAP that two of five risk factors be present before RSV prophylaxis is authorized was not associated with RSV hospitalization. However, the addition of smoking, crowded living conditions or young chronologic age to existing AAP risk factors was strongly associated with RSV hospitalization.

Importantly, the addition of all three risk factors to the five AAP risk factors (requiring two of eight) was most strongly associated with RSV hospitalization (odds ratio= 2.41, p less than 0.05.

"We believe our data provide a rationale for adding smoking, crowded living conditions, and young chronologic age to the to the existing AAP guidelines as a means of identifying unprophylaxed infants who are at risk of severe RSV disease," Dr. Makari said. "Given the known risks of RSV disease, it would be regrettable to ignore a population who might be candidates for a treatment that has been shown to dramatically reduce RSV-related hospitalizations."

RSV is a major cause of bronchiolitis and pneumonia in children less than two years of age. The disease results in approximately 120,000 hospitalizations annually in the U.S. and is the leading cause of hospitalizations in children younger than one year of age.

The study was supported by MedImmune, which developed palivizumab.

Written by Jill Stein
Jill Stein is a Paris-based freelance medical writer.
jillstein03(at)gmail.com


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