Objective: The purpose of the study was to develop and validate a clinical instrument predicting the risk of respiratory syncytial virus (RSV)-associated hospitalization (RSV-H) in premature infants born at 33 through 35 completed weeks of gestation (33-35GA).
Design: An RSV risk scoring tool (RSV-RS) was developed by entering risk factors for RSV-H, determined in a Canadian prospective study, into a multiple logistic regression model. The scoring tool was then validated externally with data from a Spanish case-control study (FLIP). The Canadian cohort comprised 1758 RSV-positive infants born 33-35GA, of whom 66 (3.7%) had confirmed RSV-H. The FLIP data set comprised 186 (33.4%) RSV-H cases and 371 (66.7%) controls.
Method: The primary outcome measure was RSV-H. The RSV-RS score was the sum of the weighted probabilities for each included risk factor multiplied by 100 and ranged from 0 to 100. Receiver operator characteristic curve analyses determined cutoff points to predict subjects at low, moderate, or high RSV-H risk.
Results: The RSV-RS included 7 risk factors and cutoff scores of 0-48, 49-64, and 65- 100 for low-, moderate-, and high-risk subjects, respectively. For the Canadian cohort, RSV-RS sensitivity in predicting RSV-H cases was 68.2%, with 71.9% specificity. With the FLIP data set, the RSV-RS had lower accuracy (61.3% sensitivity; 65.8% specificity) but showed significant positive association with increased risk for RSV-H.
Conclusion: The RSV-RS accurately identified 33-35GA infants at increased risk for RSV-H in a Canadian cohort. External validation with Spanish case-control study data further confirmed that the scoring tool is appropriate for the estimation of RSV-H risk.