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New clinical predictor indentified infants at high risk for RSV LRTI
Houben ML. Pediatrics. 2011;127:35-41.
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A prediction rule can identify healthy term newborns at risk of having outpatient-treated respiratory syncytial virus lower respiratory tract infection during the first year of life, according to researchers in the Netherlands
The prospective birth cohort study found that day care attendance, siblings in the home, high parental education levels, birth weights of more than 4 kg, and birth in April to September put an infant at 10 times greater risk for infection with the virus.
Between January 2006 and December 2008, researchers observed 298 term, healthy children born at two large Dutch hospitals. Parents of the children kept daily logs of their respective infant’s health and collected nose and throat swabs when their children had lower respiratory tract infections (LRTI). The primary outcome was that 42 (14%) infants developed respiratory syncytial virus (RSV) LRTI, defined by the combination of positive RSV polymerase chain reaction results and an acute wheeze or cough.
The area under the receiver operating characteristic curve was 0.72 (95% CI, 0.64-0.80). For their clinical prediction rule, the range of possible scores was from 0 to 5. The absolute risk of RSV LRTI was 3% for children with scores of less than 2 (20% of all participants) and 32% for children with all four factors (scores of 5; 8% of all participants). Researchers found that 62% of the children with RSV LRTI also experienced wheezing during the first year of life vs. 36% who did not have the virus.
“Clinicians can use these features to differentiate between children with high and low risks of RSV LRTI and subsequently can target preventive and monitoring strategies to children at high risk,” the researchers wrote.
Pediatricians are very familiar with the major risk factors for severe RSV infection. We always worry about the infants born prematurely, or who are born with hemodynamically significant congenital heart disease. Such infants are great candidates for passive immunoprophylaxis and many of those more serious infections can now be prevented in those cohorts. But what about the rest of our birth cohort? Nearly every child will develop an RSV infection before their second birthday, underlying risk factor or not. In much of the world, these infections are seasonal and predictable, leading to increased utilization of health care resources in both the inpatient and outpatient settings. A subset of RSV infections will involve the lower respiratory tract leading to bronchiolitis and/or pneumonia, but it’s not always clear which healthy infants born at term are more likely to develop lower respiratory tract illness.
Given the frequency of RSV infection and its associated morbidities, it would be a major advance to have the ability to predict which healthy term newborns are going to progress to lower respiratory tract infection when they develop RSV infection. The work by Houben et al in the January issue of Pediatrics helps answer this question. Among nearly 300 newborns followed prospectively for their first year of life, 14% developed a lower respiratory tract infection caused by RSV. Not surprisingly, the independent risk factors that predisposed them to this infection included having siblings and/or attending a day care, and being born during or just before RSV season. Not as intuitive were the findings that birth weight greater than 4 kg and higher parental educational levels were also risk factors.
The ability to pinpoint risk factors for the development of lower respiratory tract RSV infection in term, healthy infants brings us closer to determining interventions that will be most effective at preventing these infections. Pediatricians can use this information to identify infants who are at risk to develop bronchiolitis and pneumonia so that aggressive anticipatory guidance can be delivered to the families as RSV season approaches. Family members of higher risk young infants can be informed of the signs of progressive RSV infection, and reminded about symptoms requiring medical attention. Perhaps most importantly, simple, straightforward infection control techniques can be reviewed with parents in an attempt to prevent household transmission of RSV from other siblings.
What will the future bring? Ideally, such a predictable seasonal epidemic infection as RSV will be controlled with active immunization, and any infections treated with effective therapeutic interventions. Possibilities for both are under intense investigation, but neither has yet reached fruition. As we learn more about the specific risk factors that predispose some infants to more serious RSV infection, we should not forget the simple lessons of infection control, particularly in households and day care settings.
— Joseph Domachowske, MD
Professor of Pediatrics, Microbiology and Immunology, SUNY Upstate Medical
Disclosure: Dr. Domachowske reports no relevant financial disclosures.
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