Objective: To study the impact of the Risk-Scoring Tool (RST) as a strategy for targeting prophylaxis effectively in 33-35-week gestational age (GA) Canadian infants who range from low to high risk by evaluating the subsequent incidence of respiratory syncytial virus (RSV) infections resulting in emergency room (ER) visits and hospitalization.
Design: Prospective, descriptive study.
Setting: McMaster Children's Hospital and St Joseph's Healthcare in Hamilton, Ontario.
Participants: Premature infants between 33 and 35 weeks' completed gestation who were less than 6 months' chronological age at the start of, or during, the local 2005-2008 RSV winter seasons.
Methods: A validated, Canadian RST was used to calculate a total risk score based on seven risk factors. Only infants at moderate (RST score 49-64) and high risk (RST score 65-100) received palivizumab at monthly intervals from November to April and were followed during the respective RSV seasons. All parents received information on RSV prevention at hospital discharge. Parents of all recruited infants were contacted by telephone in May at the end of each season, and medical records were checked to determine ER visits for RSV-related respiratory tract infections and RSV hospitalization. Means, standard deviations, ranges, and percents were used to describe the variables for patients enrolled in the study.
Results: Over 3 years, 430 infants were recruited. Of these, 346 (81%), 57 (13%), and 27 (6%) were in the low-, moderate- and high-risk categories, respectively, based on their risk scores. A total of 78 (18.1%) infants received full courses of palivizumab. Six out of 57 (10.5%) infants in the moderate-risk group did not receive prophylaxis, while all 27 high-risk group infants received palivizumab. Seven (1.6%) infants were RSV-positive and five (low-risk) infants were hospitalized. One high-risk, RSV-positive infant, was seen in the ER, and discharged home. There were no statistical differences in the number of infants with RSV-related ER visits and hospitalizations within the risk category groups (p = 0.43). The limitations of this study include the observational design and the relatively small sample size.
Conclusions: The RST is a practical, easy-to-use instrument to guide judicious RSV prophylaxis for moderate-high-risk, 33-35-week GA infants. It is cost-effective, reducing hospitalization in infants who are most 'at-risk', while avoiding prophylaxis in a large segment (81.9%) of this GA cohort who are considered low risk for RSV infection.