Which syndromic case definition is most useful for RSV infections in infants?

The acute respiratory infection definition set by the World Health Organization (WHO) is suitable for initial screening for respiratory syncytial virus (RSV) among infants aged <6 months, while the alternative syndromic case definition is considered as the most robust for confirmation of cases in this population, suggests a study.

A total of 565 infants were tested for RSV, of whom 161 (28.5 percent) had laboratory-confirmed RSV infection. Among all case definitions evaluated, the most specific (95.8 percent, 95 percent confidence interval [CI], 93.8–97.8) was the one developed using latent class analyses (LCA; cough plus shortness of breath plus coryza plus wheeze plus poor feeding plus chest in-drawing). In addition, it also had the highest positive predictive value (51.4 percent, 95 percent CI, 34.9–68.0).

On the other hand, the WHO-acute respiratory infection (cough or sore throat or shortness of breath or coryza, plus a clinician’s judgment that illness is due to infection) was the most sensitive (98.1 percent, 95 percent CI, 96.1–100.0; negative predictive value, 96.3 percent, 95 percent CI, 92.2–100.0).

“Appropriate case definitions will vary depending on the content and setting in which they are utilized,” the authors said.

This study collected data on infants aged <6 months who were tested for RSV as part of routine clinical care at Children’s Healthcare of Atlanta between January 2010 and December 2015. The authors computed the sensitivity, specificity, and positive and negative predictive values of clinical features for existing syndromic case definitions used by the WHO and alternative ones constructed using LCA to detect RSV infection.

“RSV is a major cause of paediatric morbidity and mortality worldwide,” the authors said. “Standardized case definitions that are applicable to [a] variety of populations are critical for robust surveillance systems to guide decision-making regarding RSV control strategies including vaccine evaluation.”