In a study that identified independent risk factors for respiratory syncytial virus lower respiratory tract infections in a group of healthy term newborns, investigators in the Netherlands developed “a simple prediction rule” that they say can be used in clinical practice to identify healthy newborns at high risk for being treated as outpatients for these infections during the first year of life.
In the prospective birth cohort study of 298 healthy term babies born in two large urban Dutch hospitals between January 2006 and December 2008 who were followed for a year, the following were identified as independent predictors for respiratory syncytial virus (RSV) lower respiratory tract infections (LRTI): day-care attendance and/or having siblings, high parental education level, birth weight over 4 kg, and birth from April to September.
The risk of RSV LRTI was 10 times higher for children with these four factors, compared with children without these factors (Pediatrics 2011;127:35-41).
Using statistical analyses of the association between these predictors and the presence or absence of RSV LRTI, Dr. Michiel Houben of Wilhelmina Children's Hospital, Utrecht, the Netherlands, and his associates derived the prediction rule, with scores ranging from 0 to 5. The absolute risk of having an RSV LRTI ranged from 3% for a child with a score of 2 or less (20% of the children) to 32% for a child with a score of 5 and all four of these factors (8% of the children).
“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,” he and his coauthors concluded.
They noted that to date, clinical prediction models have only been developed for predicting hospitalization in preterm infants, and as far as they know, theirs is the first study that “attempts to predict the risk of nonhospitalized RSV LRTI for healthy newborns by using molecular detection of RSV.”
The primary outcome measured in the study was RSV LRTI, which was based on a positive RSV polymerase chain reaction test result and symptoms of acute wheezing or a moderate/severe cough. Parents recorded their children's respiratory symptoms with daily logs and used nose and throat swabs when the child had a respiratory tract infection. During their first year of life, 42 (14%) of the 298 children had an RSV LRTI.
With the formula they derived, 1 point was assigned for a birth weight over 4 kg, 1 point for being born from April to September, 2 points for being in day care or having siblings, and 1 point for a high parental education level. In an example they provided, a baby born in July (1 point) and who is in day care (2 points), who weighed 4.2 kg at birth (1 point) and has parents who are not highly educated (0 points) would have a score of 4 points, corresponding to a “probability of developing a RSV LRTI of 23%,” they wrote.
Because of the “extremely high” incidence of medically attended RSV infection, “children classified as being at high risk could be monitored more closely and lifestyle changes that reduce exposure could be applied,” Dr. Houben and associates added.
One of the study authors received research funding and speaker's fees from Abbott International; the other authors indicated they had no relevant financial disclosures.
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If clinicians used this type of prediction rule in their practices, Dr. Lance Chilton said it would be used to identify those at the highest risk – with scores of 4 or 5 – rather than using a low score as a basis to advise parents not to worry. Some of the factors that are in the formula are modifiable, he pointed out, noting that a score of 4 or 5 might influence parents to decide to take their children out of day care.
Dr. Chilton said that he is not aware of any clinicians who use a predictive scoring system to identify newborns at highest risk of RSV infection.
“If you asked a group of pediatricians what they used as a means of prediction as to who is at highest risk of RSV infection, most would come up with day-care attendance and older siblings, and none of them would have guessed that higher educational achievement would be positively correlated with risk of a medically attended RSV infection,” he said in an interview. “And most would say that they recommend that all babies stay away from coughing people and crowds of people during the winter virus season.”